RC Soaring FAQ

Edited by Murray Lane

Contributed to by many readers of the RCSE

Revised October 7, 1996

1.0 Introduction

This is the Frequently Asked Question (FAQ) list for the Radio Controlled Soaring Exchange (RCSE). This document is intended to answer some of the more common concerns of people getting into the hobby of RC soaring.

Some of the topics in this FAQ have set off flame wars in the past. In those cases I have tried to quote from someone whose credentials would lead one to believe s/he knows what they're talking about. Where that was not possible, I have drawn from the most understandable explanation available to me. In any case, you should understand there are different viewpoints and explanations for much of what we do in this hobby. Each of the entries in this FAQ should be viewed as someone's opinion, not gospel. Find an experienced flyer you trust and listen to them.

2.0 Beginners introduction

Sailplane plug (aka religious sermon):... don't think glider flying is just "launch, glide back"---It's very easy to get 30+ minute flights and about 1000' altitude. Remember, power flying is limited by the size of the fuel tank (about 10 minutes) and gliders are limited by the receiver batteries (about 2 hrs). And glider flying is *much* more challenging (my opinion, of course), while at the same time being easier to learn. And no fuel costs, no starting hassles, no cleanup afterwards... Also, many cities have ordinances prohibiting model engines, which means the flying fields are outside city limits. BUT, since sailplanes don't have those nasty, messy smelly things, we can fly in any large enough area!

Since a sailplane has no engine, it follows that it must always sink through the surrounding air. The trick then is to find some air that's going up faster than you'll sink through it... and for our purposes, there are two kinds of such air:

- air heated locally will tend to rise. The heating could be by the sun on a parking lot or a bonfire or a .... This is called "thermal soaring"---the columns of rising air are called thermals. This needs some skill/experience, and mostly involves smooth flying and a good idea of how your plane reacts. An easy way is to just follow more experienced fliers (some of which are birds) into them.

- wind striking a slope will rise to go over it. You just fly in front of the slope where the air is going up. With a steady wind this is easy to fly in, with challenges provided by aerobatics etc. This is called (surprisingly) "slope soaring." Landing is more challenging while at the slope unless you have a large field or something at the top.[2]

2.1 Clubs

When learning to fly model planes there are two routes you can follow. The first is slow, expensive, frustrating, and boring. The second is much quicker, much less expensive, and a lot of fun. You can 1) learn to build/fly on your own and with books, or 2) join a soaring club. When you have a question, no book or FAQ can address your exact problem as well as a club member. No book can take the controls and save your plane when it is out of control and headed toward the ground in a hurry. Join a club!

2.1.1 Local

Trying to find a soaring club in your area is the best thing you can do for yourself. Check with the local hobby shop or the public library. If that fails, look in the contest announcement section of Model Aviation magazine for a contest in your area. Call the contact person. Look in the addresses section of this FAQ. Post a message on RCSE. If all else fails, you might be able to organize your own club if you can find enough interested people. If you cannot find or create a local club, it is worth your time to drive a couple hours to the nearest club as often as necessary to get help building your model and learning how to fly it. If all else fails, buy a few good books and plan on repairing your plane a lot.

Once you find a club, let them know you are new to this hobby. You will probably be overwhelmed with help. Follow their advice in preference to this FAQ. They will know your situation better.[1]

Here's what one beginner had to say:

I just started doing RC planes myself. In fact, yesterday I flew my plane for the first time (with an instructor). He took off for me, got the plane at a real high altitude and then gave me the controls. I did OK (in my opinion) but did have to give him the controls twice in order to get the plane into stable flight again. I figured the controls would be sensitive but I did not realize HOW SENSITIVE. I only had to move them about 1/8 of an inch to turn.

There is no way I could have landed the thing without crashing.

By the way I am a full scale pilot. That did not help me at all. In fact I think it hurt. I didn't realize how much I use the "feel of the plane" when flying a real one. Obviously you have no feel whatsoever with RC planes.[2]

I once helped a stranger at the club field fly a new plane. The control surfaces had to be centered, etc., etc., but we got it up and back down to crank in more down trim on the elevator linkage. He got really excited and said it was his 6th plane, but the first that would make two flights. Seems he was a high-time commercial pilot who didn't think he needed an instructor to fly a toy. He had never figured out that when the plane is coming towards you, your right is its left. Every flight had consisted of a takeoff, turn to crosswind, turn to downwind that developed into a spiral dive into the ground or a tree. (He even pointed out the trees he had decorated.) After a couple of assisted flights, he decided he didn't need any more help and decorated another tree.[28]

2.1.2 AMA

For U. S. residents, an organization well worth joining is the Academy of Model Aeronautics (AMA). They are the modelers' main voice where it matters---they liaison with the FCC, the FAA and Congress. It is an affiliate of the National Aeronautic Association (NAA) and is the US aeromodeling representative of the Federation Aeronautique Internationale (FAI). Membership in the AMA also gets you $1,000,000 of liability insurance, without which most fields will not allow you to fly. You also need to be an AMA member to participate in contests. Besides, you also get a magazine, \QModel Aviation' which is rather good in itself, and it keeps you informed about the state of the hobby. So JOIN AMA!!! There address and phone number is given in section 10.3. Membership is $42 per year (and well worth it). [2]

2.1.3 LSF

2.1.4 Organizations outside the USA

2.2 What does it cost?

$200 - $250 is in the ballpark. $150 for a 4-ch radio, $60 for a 2m glider, covering, tools, glues, and other supplies.

2.3 How long does it take

2.4 Choosing your first plane

The most commonly recommended thermal planes on the RCSE list are the Gentle Lady by Carl Goldberg and the 2 meter Spirit by Great Planes. The Gentle Lady is a fine first plane (and a fine one to keep in your stable forever. In the right air, there is no better plane). It is a floater and will climb on a gopher belch. On the other hand it does not handle wind well. The 2M Spirit is a cleaner/faster plane than the Gentle lady and will serve you longer (assuming you don't crash it too many times). It does not climb as well as the GL and is a little more difficult to fly. Once you get past the beginner stage the poorer wind penetration of the Gentle Lady will restrict the days you can fly on. If you intend to start out flying on the slope, the Spirit is still an adequate choice. There are other planes out there (some nearly indestructible) that are better choices.

A beginner needs a plane which is stable and reacts slowly. Because beginners overcontrol, a small ship tends to react too quickly and get into more trouble than the beginner can get it out of. Consider 100" planes. The Airtronics Olympic II is no longer being manufactured as of this writing, but it is rumored it may be reintroduced. The Spirit 100 is also a good plane in this size range.[1]

If a beginner has some building experience, I would (and have) recommended the Paragon. It can really slow down and is one of the best thermaling planes. I'm not sure if they are still available, though.[51]

2.4.1 Class restrictions

2.5 Radio equipment

The radio to control your plane consists of several pieces of equipment: The transmitter (held in your hand), the receiver (carried in the plane), the servos (also in the plane, these move the control surfaces), the transmitter battery pack (in the transmitter), and the flight battery pack (in the plane).

In the United States there are 50 channels (numbered 11 through 60) available without a license. Each frequency has a bandwidth of 10KHz and lies between 72 and 73MHz. Pagers and other RF devices lie between the RC channels. If you have a HAM license you can use the HAM band to control your plane. "Toys" are controlled on the 27MHz frequencies. You should not use that band.[1]

2.5.1 Introduction & choosing the right radio

Don't bother with the cheap 2 or 3 channel sets---get a 4-ch system. It will come with NiCad rechargeable batteries and (usually) 3 servos; this is the most popular and most cost-effective kind of system. You can put the main pitch control (elevator) and the main turning control (in this case the rudder) on one stick, which is how most people (and thus most instructors) fly. The cheaper systems come with the controls on separate sticks (mode 1) and you will have tough time finding someone willing to teach you with that setup. They also use non-rechargeable cells, which can get very expensive, and sometimes have corrosion problems at the terminals. A "1991" system is so named because in 1991 the radio control frequency regulations changed, which effectively made the "old-style" radios unusable. The "old-style" radios have a separation between channels of 40 kHz. Today, a separation of 10 kHz is needed, even though R/C channels will still be 20 kHz apart---because the FCC in their infinite wisdom have created channels for pagers and such between the R/C channels, i.e. 10 kHz away from our frequencies. The Airtronics VG4 FM series is an inexpensive example, and is about $120 mail order. [U. S. specific]

If you can afford it, a system that has a "buddy box" is a really good idea. This is an arrangement where the instructor's radio is hooked up to yours, and he just has to release a button on his radio to take over control, rather than wrestling the radio from your grip. If you do this, be aware that you need to get the same (or compatible) radio as your instructor.[2]

2.5.2 Transmitters & receivers

Radios come in three basic flavors.

AM - Amplitude Modulation - The oldest technology. AM systems work well 90% of the time, but they are more subject to interference than FM systems. When interference does occur you will usually still have some control since the receiver will "average" the signal you're sending with the interfering signal.

FM - Frequency Modulation - Newer technology. FM systems are more resistant to interference. The receiver will lock on to the signal you transmit and ignore any other signals unless the other signal completely overwhelms your signal. When your signal is overwhelmed, the receiver will switch over to the interfering signal and ignore your signal. As a result it is unlikely your plane will ever see interference, but if it does, it may be fatal.

PCM - Pulse Code Modulation - Newest technology. This is simply a different way to encode a FM signal. It enjoys the inherent noise immunity of FM. The information is transmitted digitally and includes error detection information. If an interfering signal manages to overwhelm your transmitter, your receiver will recognize it as interference and ignore it. Your receiver still won't be able to acquire your signal, but it won't try to do what the noise is telling it. When a PCM receiver loses the signal it will either A) do nothing - leave the servos where they are; or B) put the servos in some default condition such as a gentle turn.

AM systems are slightly less expensive than FM. FM is significantly less expensive than PCM. I would recommend FM.

Computer radios are wonderful for advanced pilots. They are not a good idea for beginners. You will have enough to worry about without trying to program your radio.

The big radio manufacturers are Futaba, Airtronics, JR, and Hitec. There are other companies as well, but these are the biggies. Who makes the better radio is a religious discussion. People tend to be passionate about their preferences, but the differences are really pretty small. Futaba radios tend to be a little less expensive. Airtronics has a reputation for supporting soaring. Look at what most flyers in your club use and buy that brand.[1]

2.5.3 Servos

Planes use a servo to move the control surfaces. A servo is a small box with a wheel on it which rotates approximately +/- 45 degrees. This rotating motion is normally converted to a push-pull action. The force a servo applies is usually directly related to the size of the servo (and current consumption). Typical numbers are 2 to 80 inch-pounds. In 'normal' size model planes, even small servos are able to take the loads. In giant planes (1/4 scale) and high speed models, larger servos are necessary. The primary reason for choosing a particular servo is usually weight, size or cost, not needed force.[1] Relative qualities of servos

I have had quite a bit of experience with just about every type of wing servo on the market. A note about servos, all servos will degrade with time, it is just the nature of things, but how well they hold up during their useful lifetime (five years max) is the measure of a good servo. Here is a list with some background info:

Hitec HS-80(non-metal geared)...Light weight, not much torque but pretty fast. I have used these in my handlaunch plane and had no problems. However, I Have heard of guys having problems with gears stripping and having centering problems after any kind of hard landing. Not a bad servo for light duty use.

Airtronics 141...Metal geared, high torque, ball bearing. This has been around for about five or more years, sort of the grandfather of modern high speed/high torque wing servos. It was the first servo on the market to have metal gears, yet small enough to put in a wing. Most people who fly contests in California have used this servo with good success. Several problems that I have seen are: stripping of the one plastic gear in the drive train, gear shaft separating from notch in servo case, good amount of gear lash after a month or so. I have had several 141's freak out, jittering so bad that they were unusable. Entertaining to see your flaps waving to you while you fly! I quit using this servo because of the jittering and extreme slop in most of them.

Airtronics 401, the predecessor to the 141. This servo is no longer made, but it was the inspiration for the 141. The contest standard right before the 141. Guys used to use these until they stripped, and then buy a set of metal gears available locally (I think). The metal geared (modified) 401's worked great. So great that Airtronics came up with a production version.

Airtronics 501, micro, light, not much torque. See the Futaba 133 description. I have always wondered if they were the same servo!

JR 341, Small, light, fast, plastic gears. Because of it's lightweight, this servo has been used by several people in my club as a tail mounted elevator servo. It has been used as an acceptable wing servo as well. Daryl Perkins used to use them several years back in his F3B planes. They have adequate torque for driving a primary surface, but reliability of the plastic gears can be a problem. Most of these servos that I have seen have about a one year life expectancy. After that a stripped gear is inevitable. I remember seeing Don Edberg replacing gears for Daryl at the team selection in '92... not what you want to do in the middle of a contest. This is probably the best (only?) plastic geared mini-wing servo around...but it is plastic geared.

Futaba s-133/33/5102. Very small, very light, not a ton of torque. The futaba 133 has been the standard for true micro servos as long as I can remember. It makes 28oz/in of torque, which is a bit slim compared to other wing servos, but it is just adequate to drive a primary surface. I have used these for ailerons in unlimited slope racers, and for wing/fuselage in hand launch planes. Two reported problems are gear stripping, and jittering after a few months. The gears are a bit weak in the 133/33 so it is a good idea to have some spares. Some guys complain that they stop centering and start jittering after a while. Dirty control potentiometers are the cause of the jittering, and I think someone around here knows how to clean them(?). I have had a set of s-33's (the same as a 133, but manufactured with a futaba g plug) since 1984, they came with my first radio! And they work great. They are in my handlaunch and I have never had a problem with them. They are the same servos that were in the slope racer. I had to replace the gears when said slope racer met it's doom on the face of Torrey Pines, that was the only set of gears I have ever replaced. They still center great and don't have any slop. I guess I got a (really) good batch. To cure the stripping and reported centering problem, Futaba came up with the s-5102. It has a ball-bearing on the output shaft, and a brass gear set. Don Edberg uses these in his Diamant, and if I recall, Joe Wurts used these at the World Championships in 1991 for ailerons in his Eagle. This is the same case as the s-133 but with metal gears etc. It weighs a bit more than a 133 due to the metal gears. The centering can be a bit soft with this servo after a year of contest (hard) landings. But if you have a very thin wing, this servo will fit and you don't have to worry about stripping a gear.

Futaba s-3002, Small, very tough, metal gears, ball bearings. This servo is about the same size as the airtronics 141. It is a little smaller in length and height, but is a touch thicker, less than one tenth of an inch difference in thickness. This is my servo of choice. It centers very well, it is very fast, and it is very tough. It doesn't experience the heavy gear lash that a 141 does. To the guy who said that they were sloppy- I think your servos were VERY used. I have been using these for two years, and they are great. I use these for all control surfaces, wing and fuselage...and I trust them implicitly. It makes 44oz/in of torque, as much as any other mini wing servo. This servo is a little more expensive than a 141, but it is well worth the money.

Becker, I don't know part numbers, but I do know that these are the ultimate in model servos. They were very popular during the 'bad old days' of F3B. They make un-godly amounts of torque and have metal gears. Unfortunately they are VERY expensive, and impossible to get. I don't know if they are even made any more, but if you can get your hands on some, go for it![4]

2.5.4 Batteries

The batteries used in our planes come in several different flavors. The most common is the nickel-cadmium (NiCad). It's rechargability makes it very popular. Other batteries are nickel-metal-hydride (NiMH), lithium-ion, and common alkaline. Alkaline are not used often because they are more expensive (They are almost mandatory for the 8 hour LSF level V slope flight). The rechargeable batteries require appropriate care and feeding. The discussion that follows refers primarily to NiCads but the results can also be applied (loosely) to NiMH batteries. I am not familiar with the lithium ion.

NiCad battery packs are made up of individual NiCad cells. Each cell generates a voltage of 1.1 volts to 1.5 volts depending on charge and other factors. The pack voltage is simply the sum of the cell voltages. The capacity(C) of each cell depends on the size and formulation of the cell. Normally we use AA size cells which have a capacity of 500 to 900 milli-amp-hours (mAh). All the cells in a pack MUST have the same capacity. The capacity of the pack is the same as that for an individual cell.

NiCads have a very low internal resistance. This allows them to source very large currents (Electric flyers commonly pull 50 amps out of C-size cells). The NiCads we use in our transmitter and receiver are typically charged at a rate of C/10. For example, if we have a 500mAh pack we will charge it at 50mA. Once the pack is fully charged (after about 14 hours from a fully discharged pack) the pack should be disconnected from the charger. Continued charging heats the cells which causes them to be slowly damaged. You can buy chargers which will discharge and charge your batteries automatically without overcharging. Or you can just be careful.

NiCads have several faults. They develop internal shorts (see following article), they are subject to cell-reversal (caused by over-discharging), and they slowly self discharge (about 1-5% of charge per day). Despite what you may have heard they DO NOT exhibit "memory effect" in any situation you are ever likely to experience.[1]

Here's the problem. If the insulator between the plates in a cell has any holes, cracks, or defects, a little crystalline bridge will grow from plate to plate through the separation causing a short circuit. When this condition starts, the cell self discharges at a higher rate than normal. If it gets bad enough, the cell appears to be dead because of the internal short.

Even though the defect in the insulator may be there, the more you use a cell, the less likely it is for the bridges to grow. When you lay a pack up for the Winter it gives the bridges the perfect conditions for growing. Keep in mind that it isn't the layup which causes the problem. The layup only allows the condition to be more noticeable. In other words, you're not damaging your cells by just putting them away for the Winter, your just letting a defect that was already there show itself.

So, how can you avoid these problems. You can't do anything about the defect in the insulator. It's either there or it isn't. What you can do is slow down the growth of the bridges. One way is to discharge each cell individually to zero. DON'T DISCHARGE THE PACK AS A WHOLE BECAUSE YOU'LL RUIN THE CELLS!!! You have to do the cells one at a time. You can use a light bulb with two clips so you can hook the light bulb across one cell at a time and leave it for a day. Then move to the next cell. What you're doing is stopping the chemical activity inside the cells so the bridges can't grow. Once you've done each cell by itself, you put a short across the entire pack and store the pack with the shorting wire in place. The pack can be stored this way for years.

Now, having said all of this, we know no one is going to go to all this trouble. The next best thing is to just keep charging and cycling the pack as if you were using it every week. However, most of us don't want to bother and if you only do it once a month you're going to have bridges grow.

So, what do I do? I don't do anything! When I'm finished for the Fall I just put everything away that I won't be using. Not charging and cycling keeps the chemical activity in the cells low so the bridges grow more slowly. If I do find a bad cell in the Spring I don't get excited. It wasn't the Winter that caused the cell to go bad. The condition was already there and the Winter layup allowed the condition to show itself. I don't want to fly with cells which aren't perfect so rather than being upset if I find a bad cell, I'm happy that I found it!

If a cell is less than two years old I'll replace it. If the pack is more than three years old I dump the pack. Between two and three years old is a judgement call.[3]

There is a good site on WWW about NiCads that may help to answer most of the questions here and explain why they need to be "trained" before use:




>I'm thinking of building my own tx and rx battery packs. I seem to remember something about matching or balancing the cells in the packs. Could you elaborate more about this? <

Matching is not required as today's NiCad cells are quite uniform in capacity. Of course you should use cells of the same capacity rating.

> Also should I hook the cells up in series? <

NiCad cells should only be used in series, + to - and so on through the pack to achieve the overall pack voltage of 1.2 volts times the number of cells hooked together in series.

> What is the best way to connect the batteries together? Solder or spot weld? <

Soldering to cells may destroy the nylon seal. They should always be welded together. You can buy cells with solder tabs already welded on and then interconnect them with small pieces of #22 wire (stranded). It is better to buy the packs already assembled and then just add your own connector. They are available through Tower [Hobbies] in this way. There is also an ad for FMA direct in R/C Report (August 96) where they are sell receiver packs for $11.95 and transmitter packs for $24.95 including the connector of your choice. Their phone number is 800 343-2943

> Any other things I should know about connecting cells together to make battery packs? <

Hold the cells together with CA or hot melt. Tape the exposed ends of the cells so they cannot short, use heat shrink over the pack if you can get it.[46]

2.6 Building your plane

2.6.1 General guidelines

These guidelines assume you are building a thermal duration/general purpose built-up plane such as a Spirit or Gentle Lady. If your plans do not have outlines of the ribs, make your own. Either trace around the ribs or make a Xerox copy of them. You will need these when you repair your plane. Make sure your building surface is flat. If there is a warp in the table top, you will build a warp into the wings which will make the plane fly badly. Try building on a standard interior luann door. They are very flat. Don't disassemble your house, go to the hardware store and buy one with a hole punched in one side. On top of this place a piece of 2'x4' acoustic ceiling tile. When you build the plane you will use T-pins to hold the wood in place. You can push the pins through the balsa into the ceiling tile. Roll your plans out on the ceiling tile. Carefully cover the plans with plastic kitchen wrap and pin down the corners. Build directly on top of the plans.

If your plane has a spoiler option, build it. Spoilers are too useful to leave out. They greatly improve the accuracy of your landings. They help you avoid the doofus who walked into your landing circle while you were on final approach. They help your plane fly out of the brick-lifter thermal that is trying to put your plane into orbit (yes, that is a real problem).

As you build your plane, concentrate on making it strong. Many people try to minimize the amount of glue they use to save weight. For a beginner, WEIGHT IS NOT IMPORTANT, DURABILITY IS. You will crash your first plane many times. It needs to be strong enough to withstand this punishment and fly again with minimal repairs. Use lots of fillets. Make sure there are no gaps when you assemble the plane. Test fit before gluing. All joints should be tight. To fill gaps get some baking soda (not powder) from the kitchen. Work the grains into the gap. Put a drop of instant (thin) CA on the joint. The CA will wick into the baking soda and it will turn into concrete. The bond will be much stronger than the wood. Use the same procedure to make small fillets, but build the soda up a little more before dripping on the CA. Make larger fillets with balsa.

Use continuous pieces of wood for your spars, leading edges, etc. A joint will dramatically weaken the wing. If you absolutely have to have a joint, place it as far out towards the tip as possible. Make an angled joint, do not butt join the pieces. Wrap the joint tightly with a strong (not necessarily heavy) thread. Use lots of CA. If you must have multiple joints (such as the top cap and bottom cap of the main spar) NEVER align them. Put several inches between the joints. Again, no joints if at all possible.

All your trailing edges (wing, rudder, elevator) should be as sharp as is practical. The sharper they are, the more efficiently your plane will fly. You have to compromise between razor sharp and being so weak that bumping the trailing edge causes damage. Some light fiberglass epoxied to the bottom of the trailing edge will allow you to get the edge a little sharper. Don't make the edge so sharp it cuts you (I'm serious).

Build an antenna tube into your fuselage. This is a 1/8" diameter plastic tube that runs from the "cockpit" to the end of the tail. It allows you to run the receiver antenna out the back of the plane. If the antenna is not in a tube you will accidently glue the antenna into the fuselage.

When you get ready to mount the radio gear (see section 2.6.2) place the equipment to minimize the amount of lead you must add to balance the plane. The nose of the plane will carry a couple ounces of lead (section 2.7). Directly behind that will be the battery. Next back will be the servos. Last will be the receiver. When you install the battery and receiver wrap them in a stiff but compressible foam (softer than Styrofoam). This will help protect them when you crash.

Beginners always ask about aileron control versus rudders. They have studied how to fly full size aircraft and know that you control elevator and aileron with the stick and rudder with your feet. It therefore follows that the right stick used for elevator control must also control ailerons and the left stick controls the rudder. Wrong. The right stick controls elevator and your primary turning control. For a beginner polyhedral ship like you have, this means the rudder. The left stick controls your secondary turning control surface (no such thing on your plane) and spoilers or flaps. If you were building an aileron ship (your not, right?) you would put ailerons on the right stick and rudder on the left because the ailerons are the primary turning control for aileron ships. Trust me, this is the way almost everyone flies model gliders. It is easier to fly this way.

You may want to put in a little washout after your plane is built. Washout prevents tip stalls which can be deadly for beginners. I assume you covered your wings with a heat activated covering such as Monokote. Assemble the plane. Have a helper hold the fuselage flat on a table. Grab a wing tip an twist the leading edge down about one-half inch. Do not bend the wing, only twist it. Use your hot air gun to heat the covering (top and bottom). Remove the heat, wait a bit for it to cool and release the wing tip. Do the same to the other wing. As the plane sits in the sunlight the washout will slowly undo itself. As you become a better flyer you will need less washout (eventually none).[1]

2.6.2 Servo mounting

Your servos will sit in a 1/8" thick piece of plywood (airply) called a servo tray. This tray will be exposed to lots of punishment when you crash and must be securely mounted. Some advise using epoxy to mount the tray, others use Shoe Goo. The procedure is the same either way (except don't use fiberglass with Shoe Goo).

Try this method for installing ply servo trays. After cutting and fitting the tray to the fuse (and cutting the holes for the servos) roughen up the contact area inside the fuselage (if installing into a fiberglass fuse). Tack the tray into the fuse with CA (foam safe if you need to), recheck that the battery will fit past the tray. Mix up some slow curing epoxy and take some out of the batch and mix with Cabosil, Aerosil, or what ever you have, and make a fillet between the ply and the fuse (popsicle sticks work well for this). Next cut a pc. of ~3 oz. glass cloth to fit across the ply and up the fuse sides and using the straight epoxy resin cover the ply tray working the cloth right up the sides. Go easy when working around the fillets, since they are quite "soft" at this point. After the epoxy has cured cut the cloth away at the servo cutouts with an Exacto knife. I have never had a servo tray show any signs of "coming loose" with this method.[5]

You are absolutely right about "GOO" as the way to install a servo tray. Unfortunately, I was the subject of a "GOO" test this past weekend. My Super V 2M did a wicked golden arch during a launch. It went in at mach 9 totally destroying the plane --- except for the servo tray and the fuse around the servo tray --- both were totally in tact. Another facet of that "research" project is that my receiver, which was attached to the servo tray (on top) with velcro, remained in place and suffered no damage (verified by Airtronics). This is the way I will install servo trays and receivers from now on.[6]

One thing I would like to point out. If you are going to epoxy your plywood tray into the nose of your fiberglass fuselage then you should be sure that the tray extends forward and back into the fuselage past the hatch opening. The last time I epoxied a plywood tray into the nose of my plane (I believe it was my Falcon), I created stress risers at the ends of the tray and the fuse started showing stress marks and cracks at those locations from landing and dorks. Since then I started using Shoe Goo which allows the fuselage to flex and absorb the shock of landing.[7]

2.6.3 Tow hook mounting

The location of your tow hook greatly influences how high your launches are. The farther back the tow hook, the higher the launch and the poorer the plane tracks on launch. If you move the towhook too far back, the plane WILL crash on launch. As a beginner you will want the tow hook fairly far forward. As you get better you will want to move it back. You can put multiple tow hook locations in your fuse or put in a movable tow hook. I recommend a moveable tow hook. To install one, locate where the plans recommend placing the tow hook in the plane. Epoxy a layer of heavy fiberglass at this location. The fiberglass should be the full width of the fuselage and four inches long centered on the plan towhook location. Get (or make) a bolt two inches long and 3/32" to 1/8" in diameter. One inch of the bolt should be threaded, the upper inch should be smooth. Get two nuts, two one-half inch washers, and a lock washer. Cut off the head and put a 95 degree bend in the bolt where the threads meet the smooth portion of the shank (angle should be slightly acute). This is your new towhook. Cut a slot in the bottom of the fuse extending one inch in front of and behind the plan towhook location. The slot should be as wide as your tow hook. Make sure the slot runs exactly along the centerline of the fuselage. Round the ends of the slot. Create a wood block out of spruce or other dense wood. The block should be one-quarter to one-half inch thick and about two inches square. Trim as necessary so it fits neatly in your fuselage. Drill a hole through the center the wood block. Put a nut and washer on the towhook. They should be twisted on all the way down to the bend. Place the block in the fuse and push the threaded portion of the towhook through the fuse slot and the block hole. Put the washer, lockwasher, and nut on the portion of the towhook sticking out the top of the block. Adjust the nut on the outside of the plane so there is about 1/4" between the towhook and the bottom of the fuse. Move the towhook to the plan location and tighten the internal nut. The towhook should point backward toward the tail.

As your flying skills improve you will want to move the towhook for better launches. When moving the hook back, mark its current location before moving it so you can know how far you moved it. Never move it back more than 1/4" between test launches and 1/8" is recommended. When the plane starts to become hard to control, slide the hook forward a little.[1]

2.6.4 Wiring

Using a microphone jack in place of the on off switch:

Radio Shack has what your looking for. Submini 3/32 2.5mm phone jack closed circuit type cat. no. 274-292 and the cat. no. 274-290 phone plug to go with. Just wire so that power flows through the charge plug to the battery and interrupts flow from battery to receiver when the plug is inserted. And so that it completes the circuit between battery to receiver when the plug is removed. This can save about 10 grams over the normal battery switch. And it is an example of the kind of technical soaring gems you can get out of a Waco tech news letter.[8]

Editors note: If you use this method attach a big red "remove before flight" ribbon to the plug. Also consider that the phone jack was designed to carry low current levels and may not be reliable with the (relatively) high currents drawn by the servos. Having said that, I've never heard of a problem that was traced to poor contacts on the phone jack.

2.6.5 Visibility

When you cover your model you should consider how to make it more visible. You will be flying your plane up to one mile away (yes, really). At those distances you will need all the help you can get to see it.

The problem here is sometimes called contrast gradient in photography. The upshot of this is that if you have a high contrast between the object and the background you can distinguish it from the background. The eye works initially by scanning for edges, it first picks up the edges of an object (the detail comes later) and then the brain takes over to make sense of the data. You can blind test this in a very dimly lit room with a strange object, if the shape makes sense you can recognize it. Equally if the object has soft edges it may not be seen or recognized.

With models we know the shape from almost every angle so recognition is not a problem. What we need to be able to track it is a good contrast with the background. Unfortunately the changing conditions require different colour schemes to achieve this. A white model is very easy to pick out in a blue sky, or against the ground. This is particularly true of sailplanes in flight, if you are above them you can easily see the aircraft. I once had a pair of Tornado's fly below me when I was parked in lift over a prison (taunting the poor bastards in the exercise yard), in the K 8 you could hear them but they were only visible when their camouflage didn't quite mix with the background and not so easy to see after you had them spotted. A bit frightening to say the least, although there was a momentary temptation to put the nose down and yell "ATTACK, ATTACK, ATTACK". The point is that their camouflage for low level flight had two things going for it; the contrast was low and the pattern disrupted the shape.

So for long range visibility we need to design for the conditions. The contrast gradient is what we are looking for because colour of itself fades out quickly at distance. Even dayglow colours are not much use at 500 metres. So what colours give good contrast? Black should be good against grey skies but it seems to make the model look smaller for some reason. Red is a favourite in the U.K. (particularly transparent red Solarfilm on open structures), it seems to suit our conditions best, plenty of cloudy and grey days, but it is not quite as good on blue days. White and yellow are good on blue days. Orange is good but a bit close in tone to a grey sky at distance. I had a yellow model with fluorescent orange undersides, it looked like a Buttercup and was great on sunny days, but easy to lose on grey days.

The shade is perhaps the key element, pastels are not too good being essentially a light tone. Solid red comes out in black and white photography as being around a 60% shade of black and this seems to be what is required. It does not really matter if the colour is green, blue or purple for U.K. conditions, at distance it is only the shade that you see.

My solution is to paint the extremities of the model in darker colours. The whole tailplane is in a dark colour, usually bright red as is the underside of the wing, the top surface having red tips. On small models I would tend to paint the nose too.

The reflective tapes are o.k. but I find that their flash in sunlight sometimes blinds you to the outline of the model with a possible loss of orientation. At extreme distances they only act as a marker, which may be what is required. The hologram tapes I really hate for snobbish reasons, they look cheap and tacky, that's what comes of being trained as a designer.[9]

Editors note: I have found yellow on the top of the wing and blue or green on the bottom works very well. Always put the light color on top and the dark color on the bottom.

2.7 Static plane trim

To get static trim on your new or rebuilt plane do the following steps:

1) Place the plane on a balance box and add (or remove) nose weight to balance the plane at the CG point shown in the plans. If no point is shown, balance at 35%. A balance box is a simple contraption. To build one, but down a piece of plywood about 8" by 14". Stand a pair of 14" 2x6's on edge on either side of the plywood so the whole thing makes a 'U' shaped channel. Place a 1.5" long, 1/4" diameter dowel on each 2x6 about 2/3 of the way along the 2x6 and perpendicular to it. The dowels should line up with each other exactly. Glue/nail all this together. Place the plane (fully assembled) in the channel so the wings rest on the dowels. Slide the plane back and forth on the dowels until the plane balances (touching nothing but the dowels). Measure the distance from the CENTER of the dowel to the leading edge of the wing (both wings MUST measure the same or the plane is twisted on the balance box). Divide this distance by the root chord of the plane. This should be about 35%. Note that if you have swept wings or other wing 'malformations' this will not be accurate, but it is fine for 95% of the planes out there. This isn't meant to be perfect, just a good first start.

2) Take a three foot length of string. Make a small loop in each end. Hook one end over a hook in the ceiling. Hook the other end over the towhook on your fully assembled plane and hang the plane upside-down from the ceiling. The plane should not be touching anything except the string. Tape finishing nails to the tip of the high wing until the wings are within a couple inches of the same distance from floor to wing tip. Remove the plane from the string. Push the nails into the balsa block at the wing tip so they are totally enclosed in the wing.[1]

2.8 First flight

2.8.1 Special pre-flight

Okay, your plane is assembled, covered, and balanced. Your radio is installed and you've watched the control surfaces move as you move the sticks on the transmitter. You can`t wait to get it in the air. Calm down. At this point I have to remind you to get help from an experienced flyer. You've put a lot of hard work, time, and money into your plane. You don't want to crash it now. At this point the experienced flyer will check several things. These must be checked on a new plane or after any crash. The correct answer to all of the following questions is yes. If you get a "no", fix the problem and start over.

Are all electrical connections tight? Is the receiver antenna fully extended? Are the receiver and battery protected from mechanical shock? Are all the control linkages tight? If you grab a control surface and wiggle it does the servo hold it steady? Are the hinges solidly attached? Are all the snap links closed? Are the control horns screwed down tight on the servos? Do a frequency check (section 2.8.2) and turn your radio on. With the trims centered do the control surfaces line up with their respective stabilizers? Stand behind your plane. Push the control stick right. Did the trailing edge of the rudder deflect to the right? Did the rudder deflect 20 to 30 degrees? Push the stick left. Did the rudder follow? Did the rudder move about the same distance in both directions? Release the control stick. Is the rudder still aligned with the vertical stab? Push the stick forward. Did the elevator droop down? Did the elevator deflect 20 to 30 degrees? Pull the stick back. Did the elevator rise? Did the elevator move about the same distance in both directions? Release the stick. Is the elevator still aligned with the horizontal stab? With the throttle pulled all the way back, look at the spoilers. Are they completely closed? Slowly push the throttle stick forward. At first nothing should happen. Then the spoilers should start to open. If you used magnets to help hold them closed they may pop up a little instead of moving smoothly. Is that what happened? Continue pushing the throttle stick up. Are both spoiler blades moving at the same rate? Push the throttle stick all the way up. Are both spoilers open the same distance? Are they open at least 70 degrees off the wing surface? Slowly pull the throttle stick back. Do the spoilers move smoothly? Move the throttle stick all the way back. Did both spoilers close ALL THE WAY? Cycle the spoilers open and closed slowly a few times. Do they work properly every time?

If your plane has a wing span greater than 100 inches, skip to the normal pre-flight section. For smaller planes the next step is a hand toss. Bigger planes are too heavy to hand toss reliably. They are more likely to be damaged.

Find a large open field. A high school football field or park will do nicely IF THERE ARE NO PEOPLE AROUND. Never fly around non-flyers. A corollary to Murphy's law says you will hit them. The field should be reasonably flat. There should be little or no wind. Consider that you WILL crash into any fence posts, playground equipment or picnic tables within 100 feet. Complete the normal pre-flight (section 2.8.2). Hold the plane in your left hand (I don't care which hand you write with, I said LEFT). You should be gripping the fuse between the center of the wing and the trailing edge. It should feel comfortable and reasonably balanced. If the wind is blowing hard enough to move the plane at all, it is blowing too hard, go home. Hold the transmitter in your right hand (Americans don't use those wimpy flight trays). Grip the right control stick with your thumb and forefinger. Now establish the mind set that you are NOT going to control the plane during this flight. You will only move that stick if things are going seriously wrong. Face into the breeze. The noise it make as it blows over your ears should sound equally loud in each ear. Lift the plane over your head and reach back as far as possible. Look at the plane. Is it flat? Check pitch, roll and yaw. All should be aligned with the breeze. Throw the plane hard straight ahead. Do not throw it up. Do not throw it down. Throw it straight. If you have thrown it correctly it will move out ahead of you on a straight line. If it curves gently use the stick to GENTLY straighten it out. Do not attempt to land the plane. Let it continue on it's course until the ground comes up to meet it. Congratulations, you're not a virgin anymore.

If everything went smoothly you are ready to move on to your first launch. If the plane did not fly fairly straight you have to figure out what went wrong. First check for damage to the plane. Repair any you find. There are two likely sources for problems: 1)You did not throw the plane flat, 2) You did not build your plane straight. Hand tossing the plane a few more times should eliminate number 1. If you've decided your plane is not straight there are three places to look. If the plane rolled when thrown you have a wing twist or warp (this is the worst). If the plane pitched (dive or climb) you have a problem with decalage. Check the wing saddle and horizontal stabilizers. If the plane yawed left or right (probably leading to a roll) your vertical stabilizer is crooked. Fix any problems and start this section over.[1]

2.8.2 Normal pre-flight

It's a beautiful day and you've arrived at the flying field. You've assembled your plane and you're ready to fly. Right? Wrong. You have to do a few checks before EVERY flight.

1) Check the frequencies of the other flyers before turning on your radio. Normally your club will have some kind of frequency control. Ours uses clothespins with channel numbers on them. You must have the clothespin attached to your antenna before you turn on the radio. Yours may be as simple (and error prone) as simply calling out your channel number and listening for a response. No response means your channel is clear. Check with your tribal elders. Failure to follow your clubs convention may cause a "shoot down". This occurs when your transmitter signal jams the signal from the flyer legitimately using that channel. The receiver in the plane does not hear any signal clearly and decides the best place for it to be is underground. The results are not pretty.

2) Check that the receiver and transmitter are fully charged. You can look at the ESV on the transmitter to verify the transmitter pack is charged. The flight pack is not so easy. You can measure the battery voltage but that won't help unless you've characterized your batteries (another FAQ). If you treat your flight pack and transmitter pack the same (charge together, run together, turn off together) you can rely on the transmitter ESV. Just stay out of the yellow zone on the meter.

3) Perform a range check. This only need be done after you assemble your plane at the field, not before each flight. Get your frequency pin. Place your plane on the ground turned on. With your antenna collapsed, turn on your transmitter. Standing next to your plane you should be able to control your plane with no problem. Have a helper stand next to the plane and wave every time s/he sees the rudder move. Walk away from the plane periodically pushing the rudder stick. Watch for your helper to wave. Keep moving away until your helper doesn't wave or you get to about 200 feet. If your helper stops waiving at less than 100 feet you have a problem.

4) Extend your antenna. I know this sounds dumb but you would be amazed how many people fail to do this. The plane works just fine until it reaches the end of the launch. At that point it flies out of collapsed antenna radio range Then it just burrows into the ground or flies away. Dumb.

5) Give your plane a good shake. You should not hear any rattles. The control surfaces should not wiggle.

6) Using the transmitter deflect all the control surfaces. Watch the surfaces move, don't just listen. I once broke my elevator control rod on a hard landing. Prior to the next launch I listened to the controls wiggle and launched. It went up the line beautifully. Nothing happened when I tried to do a loop. I was lucky that the elevator hinge happened to hold the control surface in a neutral position. The plane eventually landed itself.[1]

2.8.3 Launch

Your experienced flyer will do the first launch. This is what s/he will do. I assume the launch will be off a hi-start (Operating a winch would require a whole FAQ). A correctly executed launch is a near-hands off operation. Little control is necessary. The hi-start will be stretched appropriately (section 3.4.1). Attach the ring to the towhook and throw the plane. The plane will immediately rotate from horizontal to near vertical. Some slight rudder control may be necessary to make sure the plane flies straight. As the plane arcs over the spike holding the hi-start down the hi-start parachute will slip off the towhook. Yes, it really is that easy. There are two reasons an experienced flyer should do the first launch. 1) You will try to overcontrol the plane before you are two mistakes high and turn this simple launch into a lesson on repairing your plane. 2) If a gust of wind hits your plane at the moment of release your plane will crash unless it receives the correct control inputs very quickly. You don't have time to think which way to turn or how hard.[1]

2.8.4 Flight

Your plane has just come off the hi-start. The experienced flyer has done some minor trimming and is handing you the transmitter. It's time for the most important lesson you can learn. Take the transmitter, but don't touch the sticks. Watch the plane, it is flying smoothly and isn't crashing. Lesson #1: The plane flies best without you. That's great but the plane is starting to get a little distant. Move the rudder control trim four clicks to the right. Your plane will start a gentle right turn. Note that you haven't touched the sticks yet. Let the plane do a full 360 degree turn. If there is any breeze you will note that the plane does not describe a circle, but an oval. Now move the rudder trim six clicks to the left. The plane will straighten out. Before it has a chance to start turning left, move the rudder trim two clicks right. Put in three clicks of down trim. Notice how the plane picks up speed. Take the three clicks back out. It may take a while for the plane to slow back down. Okay, the best part of your flight is over. It is time to touch the sticks. You are going to attempt to duplicate the turn you did earlier using the trim adjustment. This time you will turn left. Push the stick gently to the left. The top of the stick should probably move no more that about 1/8". Remember the bank angle you saw before and try to maintain that. Do not press the stick forward or back. Do not worry about the planes apparent speed, worry about the bank angle. When the plane is pointing straight into the wind again push a little right stick to cancel the turn and release the controls. Most likely what happened during that turn is you pushed the stick too far to the left, the plane started a roll, nose toward the ground. You panicked, pulled full up elevator (overstressing the wings). The plane pulled up into a stall and nosed down again. Hopefully at this point your experienced pilot took over and stabilized the plane. Over controlling is the number one problem of beginners. Be gentle. In any case, the plane is now down to about 50 feet and it is time to think about landing.

One other issue before addressing landing. Being a good student you did your first flight on a near windless day. Eventually you will start flying in the wind. When you do you will notice the plane goes downwind a heck of a lot faster than in goes upwind. This causes two problems. If you look at the speed at which the plane covers ground while going down wind you will conclude the plane is flying too fast and pull back on the stick, causing a stall. Wrong. The planes airspeed does not change when it flies downwind. Do not pull back on the stick. The other problem is getting too far downwind. When you turn the plane back into the wind it's ground speed will be much less than it was when going downwind. It may take a long time to get back. You may run out of altitude before you get back. If your plane is a long way downwind you may never find it. Do not fly more than a few hundred feet downwind until you learn the capabilities of you and your plane.[1]

2.8.5 Landing

You have made it to the only non-optional portion of your flight. Your plane is about fifty feet high and slightly upwind of you pointed into the breeze. Your experienced pilot will be making this landing. First s/he will put in a few clicks of down trim. This ensures the plane is well above stall speed for the maneuvers that follow. The pilot will initiate a fairly hard turn and straighten the plane out headed downwind. Depending on the speed of the wind, the planes airspeed, and sink rate the pilot will fly the plane downwind for anywhere from 0 to 15 seconds. S/he will then turn back into the wind with the plane pointed more or less straight toward him/herself. The plane will slowly settle toward the ground. Turbulence will randomly cause the plane to roll and yaw. The pilot will use the controls to keep the plane on track. As the plane gets within about a foot of the ground the pilot will gently pull back on the stick to flatten the glide and slow down. The plane will not rise during this flare maneuver, just not sink so fast. As the plane runs out of energy it will settle on to the ground and slide for 5 to 15 feet before stopping with the nose just touching the pilots toes.

After a number of flights your experienced flyer will decide you are ready to land you own plane. You will forget to add the down trim which will contribute to your problems later. You will make a flawless downwind turn. You will take too long to initiate your turn back into the wind and end up with the plane much too far away. As the turbulence causes your plane to roll and yaw you will get confused which way to turn since the plane is now pointed toward you instead of away from you. Instead of turning against the turbulence you will turn with it. Your plane will start to spiral in. Suddenly realizing your mistake you will snap the rudder around the other way and pull back on the stick to make your plane go up. True to your commands your plane will slowly begin to cancel the roll and slow down, causing a stall. The inner wing tip will hit the ground first followed quickly by the nose. After the dust settles and a long walk you will find only minor damage which can be repaired at the field.[1]

2.9 Flight trimming

After building your plane according to the manufacturers instructions your plane will fly okay, but there is plenty of room for improvement. The adjustments you make are called flight trims and have little to do with the trim levers on your transmitter. Your experienced flyer may make these for you but sometime after you do a full solo flight you should do them yourself so you can understand your plane better. The adjustments should be made in the order shown.

The first adjustment you make will be to your CG. You will use the dive test to determine how to move your CG. Ideally this should be done in the early morning of a windless day. You don't want thermals or turbulence confusing you. Launch the plane and adjust the trim levers so the plane flies straight at a nice cruise speed (a little on the slow side). You should be at least 200' high at this point. With the plane flying across your field of view, put the plane into a 30 degree dive. Let the speed stabilize and release the controls. Watch what the plane does for a few seconds (don't crash!), then use the controls to return to level flight. Land the plane. The plane should have slowly pulled itself out of the dive. If the plane pulled out of the dive quickly (usually pulling up into a stall), remove nose weight. If the plane increased it's dive rate (tucks under), add nose weight. How much weight you add or remove depends on how violently the plane pulled up or tucked under. For a 100" thermal plane you would add or remove about one ounce for fairly violent climbs or dives. Repeat the dive test with the new nose loading (remember to trim for level flight before diving). For Newbies it is better to have too much nose weight (so the plane pulls up a little too quickly) than too little. Don't bother with weight changes of less than 1/4 ounce.

The next item to adjust is the control surface throws. There is no point in having any control surface deflect more than about 25 degrees (except for flaps and spoilers). More deflection than that does not give you more control, it simply generates more drag. Less than 25 degrees may not give you enough control authority in an emergency. To set the control throw measure the length of the control surface parallel to the fuselage. Many elevators are 3/4", we'll assume that's what you measured. Multiply that measurement by 0.42 (0.75 * 0.42 = 5/16"). Using the transmitter move the elevator full up (pull back on stick). Turn the plane off so the elevator stays up. Put a straight edge along the bottom of the stab and measure the gap between the straight edge and the trailing edge of the elevator. If the measurement is greater than the number calculated earlier (5/16") move the control rod in on the servo arm or away from the hinge at the control horn. If the measurement is less, move the other way. Turn the plane back on and check the new throw. Repeat his for the rudder. If your rudder has an unusual shape, measure the throw at a middle point. The control throw does not have to be exactly 25 degrees, just around there.

Next, adjust your trims. On a windless day launch your plane and adjust the elevator trim so the plane flies at whatever speed you like to see it fly at. Then adjust the rudder trim so the plane tracks absolutely straight. Fly it straight toward or away from you to check this. Land the plane without touching the trims. Look at the trim lever position. Is it in the center of the trim range? If so, your done. If not, turn the threaded clevis to center it. Write down which way you turned it and how many turns. Repeat the test flight. Now you'll find out you turned it the wrong way. By writing it down you now know the correct way to turn and how much.

The final adjustment is the towhook. Mark the current position of the towhook on the fuselage. Center the elevator trim and launch your plane. Watch how it climbs. If it tracked smoothly up the line you should move the towhook back. If the plane turned from side to side you should move the towhook forward. Move the towhook in 1/8" increments. Repeat your adjustments until you have to provide a little steering on the way up but mostly the plane flies itself. Note that if you move the towhook back too much the plane will be totally uncontrollable and WILL crash on launch. Move that hook backward in SMALL steps![1]

2.10 Repairs

You will crash. When you do you'll have to evaluate if the plane is salvageable. Don't try to make that decision at the field. Most planes are repairable, but it may not seem like it when you've just watched your pride & joy dive in from 200 feet. Pick up ALL the pieces (no matter how small) and take them home. Wait a day or two until you can look at that pile of balsa objectively. If the damage is severe (wings in multiple pieces) remove ALL covering and look for hidden damage. If the damage is less severe cut the covering back a couple inches away from the obvious damage. Slice out any damaged pieces at an angle so your joints are not butt joints. Completely remove any ribs you don't have all the pieces to.

Now is the time to decide if it is worth repairing the plane or if it is time to buy a new one. Consider how long it will take to build a whole new plane. Consider if you have learned all that this plane can teach you. In most cases it is better to repair what you've got.

Each repair situation is too different to give more than general advice. Any spar breaks should be significantly over-reinforced. Use lots of thread wrapped tightly around joints and glued with CA. Check alignment every step of the way, it is really easy to build a warp or twist into the wings. Fiberglass is wonderful stuff - use it.

After you've completed the structural repairs (but before re-covering) assemble the plane. Look for alignment problems. Bend the wings like you've seen them bend on launch. Listen and look for other damage. When your satisfied everything is correct you can re-cover the plane. Repeat all the checks in section 2.7 and 2.8.1.[1]

2.11 Second plane

Most beginners want to move on to a second plane before they have learned all their first plane can teach them. It's your choice but I would recommend flying the same plane for at least a year unless it suffers an irreparable crash. Also consider that a new set of wings on an old fuselage can completely change your planes flight characteristics. Try longer wings, different airfoils, etc. A Phillips Entry on Oly II wings dramatically improves the way that plane flies. Talk to other club members, find out what they like.

When choosing between another polyhedral ship versus an aileron ship you might consider contest performance. The contest scores in our club clearly show that rudder/polyhedral planes beat aileron ships in thermal duration flying. Those results are independent of the pilots (i.e. give a good pilot a polyhedral ship and he will beat the equivalent pilot with an aileron ship).[1]

After following RCSE quest for perfect Second sailplane (Intermediate), my vote still goes to the Pierce Aero GEMINI MTS. The Gemini seems to fit the requirements: Around $85, excellent flier, STRONG, NO bad habits. Only drawback it needs lots of carving & sanding. With 2 oz. glass on fuse it will match strength of fiberglass molded fuse, and can be made just as clean. I have flown it with 2M, 100", and 115" wingspans. The standard 100" works best as designed. The longer wings float better but you give up control, especially on landing. It could use spoilers; top and bottom are best to cancel pitching moment (no computer radio compensation)

My first was one of first 50 kits made and lasted many years. It finally met its demise upon launch with reversed elevator on a night flight! (By this time I now had a computer radio that could select with great precision the wrong aircraft number!)

Number two is still flying with 118" wing. I use top spoilers of the Graupner blade type, and Split flaps on the bottom at the TE. The flaps are about 1 by 14 inches of 1/64 ply, taped on, reinforced with .007 carbon batten strips. I trimmed the flaps down in size, incrementally, with scissors to balance the pitching moment.

Both planes excellent fliers, and seem to enjoy vertical-eights to kill off energy while returning from a thermal. As an intermediate plane you don't have to worry about its strength; it wont break in the air or on winch launch. You have to watch for the ground, though. [10]

3.0 Thermal soaring

3.1 The plane

3.2 The lift

Gliders get their motive power from two primary sources: rising bubbles of warm air called thermals, and wind that has been deflected upward by a ground obstructions called ridge or slope lift. This section deals with thermals.

An article follows which gives more information, but in general thermals are a bubble of warm air. They have a `core' where the air is rising faster than at the edges. They form as blobs of air heated by the ground (or other heat source) that break loose and climb through the atmosphere. Thermals drift with the wind. Since your plane is (hopefully) in the thermal it will drift too.

Thermals are found primarily by watching your plane (see section 5.4). If one rises under your right wing it will lift that wing more than the left. This will cause your plane to bank to the left. When you see that happen you should A) turn hard against the thermal induced bank and drive back into the thermal or B) turn hard with the thermal induced bank and make a 270 degree turn. Straighten back out and drive into the thermal. Personally I prefer option A. You may also detect a thermal by the tail rising unexpectedly. Turn 180 degrees and drive back into the thermal. Once into the thermal your plane will begin to rise (or at least sink less). You must now `core' the thermal. Search for the portion of the thermal with the greatest lift. I do this by starting a turn about 100 feet in diameter. It does not matter if the turn is clockwise or counterclockwise. If someone else is already in the thermal turn in the same direction they are (to reduce the chance of collision). Hold your rudder stick at a fixed angle so the plane would maintain a constant circle assuming no outside influences. Watch the plane carefully. At some point in your circle the plane will increase its bank angle because of the thermal. Turn slightly against the increased bank angle to try to return to the bank angle you started with. Around 180 degrees later your plane will tend to flatten out. Turn slightly harder. Try to keep your bank angle constant throughout the circle. After a few circles you will have `cored' any medium sized thermal. Keep circling and your plane will climb. Remember to keep the bank angle constant and ignore the planes position relative with the ground. The plane and thermal will drift with the breeze. If you are in a small thermal you must decrease the diameter of your turn. In extreme cases you will see people stand their plane on one wing tip and turn in just a few feet (That's hard to do). In large thermals you should flatten out your circle - make it larger. You can get a clue how large the thermal is by how fast it lifts. Large thermals tend to lift slower. That is a tendency, not a rule.

Beware of bricklifters. These are thermals that are so strong that they will lift anything. Once you stumble into one you can do no wrong. You hardly have to worry about coring the thermal `cause everywhere is up. That's fine while you're at 200 feet. Once the thermal has lifted you to 3000 feet you're in trouble. You'll get up there and find out your having problems getting out of the thermal and your plane is getting really small. There are two ways to get out of trouble. Neither is guaranteed. If you have a fairly slow polyhedral plane (like a GL) pull the control stick all the way back to the lower right corner (this technique will not work with a straight wing plane). Hold it there. Your plane will do some nasty turns and start spinning. If you are still not dropping, open your spoilers and hold the spin. After you drop out the bottom of the thermal close your spoilers and release the controls. Don't try to straighten your plane out, it will take care of itself. The second method works better with faster planes. Simply pick a direction and keep going. Move your elevator trim all the way down. Push in a little down stick to help get started then release it. Don't let the plane get going too fast, but you want to move as fast as you feel comfortable with. If you are still climbing open your spoilers. Don't turn, don't try any maneuvers. Eventually you will get out of the thermal. Close your spoilers, slowly move your elevator trim back to neutral and let the planes speed bleed off.[1]

I highly recommend the article by Roland Stull in the last proceedings of the Madison Soaring Symposia. See the classified ad in RCSD for how to order that volume.


What do thermals look like?

Copyright 1995 by Wayne M. Angevine

May be freely redistributed on Internet as long as this message is included.

Model sailplane and free flight fliers are interested in the structure of thermals, which provide the energy for their flying. Here is my attempt to describe thermals. I'm an atmospheric physicist working in the boundary layer. This is not a scientific article, but my views based on extensive reading and observations.

The short answer to the question is that thermals are columns of rising air. A longer answer requires what may seem like a digression into boundary layer physics.

The boundary layer is the layer of air near the earth's surface that is affected by the surface on scales of an hour or so. The sort of boundary layers we're interested in are *convective* boundary layers, which occur in the daytime over land in weak to moderate wind conditions. There are other sorts, but they don't produce thermals as such. I'll also assume relatively flat and uniform terrain, and at most fair-weather cumulus clouds. Boundary layer physics is a subfield of atmospheric physics or meteorology, but the scales (and therefore the forces) of interest are different. It is easy to become confused if one tries to apply basic large- scale or storm-scale meteorological concepts to the boundary layer.

A convective boundary layer is a few hundred meters to 3 km thick, depending on the amount of incoming solar energy, the amount of moisture in the ground, the larger-scale weather (high or low pressure), the wind speed, and other factors. Call the boundary layer height zi. The bottom of the boundary layer is a *surface layer* about 0.1*zi thick, say 100-200 m. The surface layer is heated by contact with the surface. The top of the boundary layer is a temperature inversion (hence zi, inversion height).

So to first order, thermals are columns of warm and therefore buoyant air that rise from the surface layer to the inversion. The spacing between thermals is about 1.5*zi, say 1-2 km. The thermals themselves are somewhat less than half that, say 500-1000 m in diameter. Most thermals span the boundary layer vertically. There is, of course, a distribution of sizes. Between thermals are broad areas of sink. The sink is weaker than the lift because it covers a larger area. The opposite is true at the top of the boundary layer, but we rarely fly that high.

There are, as always, complications. Sometimes we fly in the surface layer and sometimes in the lower part of the boundary layer. Rising air in the surface layer (the lowest 100-200 m) is in the form of small plumes, themselves a few tens of meters in diameter. These plumes converge near the top of the surface layer to form thermals. The surface layer to boundary layer transition is not sharp, so we often find ourselves flying in either well-organized thermals or disorganized plumes, or some of both.

Thermals evolve over time, are influenced by terrain, and are shaped by and move with the wind. Boundary layer thermals form and dissipate with time scales of 10-30 minutes, surface layer plumes faster. This can lead to the apparent phenomenon of "bubbles" or detached thermals or plumes. Plumes and thermals respond to irregularities in the surface (different amounts of vegetation, houses, and so on) by forming more often in some places than others. Dark ground (if it's not wet!) and sheet-metal roofs are well- known thermal concentrators. If the wind is light, thermals may stay attached to the hot spot. If not, thermals may form repeatedly over the hot spot and drift downwind. Thermals drift with the average wind over their height, so they may travel at a higher speed and in a somewhat different direction than the surface wind. Thermals also tilt if the wind is stronger at higher altitude, the usual case.

Thermals are not uniform, nor do they have sharp edges. The edges interact with the surrounding air, so thermals have a warm, usually fairly smooth core surrounded by turbulent edges. The air around the edges may be in the form of blobs and may be either rising or sinking. This leads to the common idea that thermals are toroidal (donut-shaped). It's probably more accurate to think of thermals as vertical cylinders. Roland Stull (see reference at end) writes, "...the best model might be the 'wurst' model...", that is, that thermals look like vertical sausages. Air detrained from the thermal edges is cooled, and cannot be recirculated into the thermal except at the ground. Vortex rings of the size of thermals are not observed. Stull also writes, "Real thermals are not perfect columns of rising air, but twist and meander horizontally and bifurcate and merge as they rise."

The strength of thermals is controlled by the amount of sunlight and the surface conditions. If the surface is wet or moisture is being emitted by healthy plants, a larger fraction of the incoming heat from the sun will be used to evaporate water than to heat the air. Water vapor does contribute to buoyancy, but less than heat does. These factors probably account for most of the difference between soaring conditions in the western and eastern U.S.

So far I've described the situation in the middle of a day with light wind and high pressure. I wish all contest days were like that! If the wind is stronger, turbulence driven by wind shear may interfere with the formation of thermals and the lift will be light and spotty. If the barometric pressure is low, there will likely not be an inversion to define the boundary layer top. This will tend to produce larger thermals that are farther apart, at least until the rain starts!

Do thermals rotate? They do, but not predictably. Even dust devils don't have a preferred direction of rotation (see Stull, p.449). Thermals are too small and too short-lived to be affected by the earth's rotation (Coriolis force) or by the equator/pole thermal gradient. Their rotation is determined by local terrain. Rotational velocity in the core of a typical thermal is small compared to the vertical velocity.

Those who are interested in following up the topic further can consult the following references. An Introduction to Boundary Layer Meteorology, by Roland Stull (Kluwer), should be in any good University library. The chapter on convective boundary layers is quite readable. A recent paper on imaging of the boundary layer is by Schols and Eloranta, Calculations of Area-Averaged Vertical Profiles of the Horizontal Wind Velocity from Volume-Imaging Lidar Data, in the Journal of Geophysical Research, vol. 97, pp.18,395-18,407, 1992.

3.3 The ideal flying site

The perfect flying site is a large, freshly paved parking lot several miles out of town. A well maintained sod farm is on one side of the parking lot. The whole thing is surrounded by a five foot earthen berm. There are no power lines or trees in the area. The sun heats the parking lot creating a bubble of warm air. The berm protects the warm bubble from any breeze until it is hot enough to break loose. The sod provides a soft surface to launch and land on.

Thermal sites are easier to find than slope sites. Mostly you just want a big open field with few trees or other obstructions. You want few people (other than flyers). Dry is good. Sod farms surrounded by open fields are really nice.

Be very careful about launching and landing around non-flyers. Because our planes are nearly silent people will not notice them until they get smacked in the back of the head. Not good. Most fiberglass ships carry more than enough energy to kill someone.

3.4 Launch methods

3.4.1 Hi-starts & bungee cords

To launch your plane you don't need an engine. If you can find a club, they will probably have a winch you can use. That is the best launch system. They can be expensive, so you probably don't want to buy one for yourself. Next choice is a hi-start. You can get one for under $50 (US). It is simply 30 meters of 8mm surgical tubing with 125 meters of string attached. You nail the end of the surgical tubing to the ground and stretch it out to about 100 meters. Attach the string to the towhook on the bottom of your plane and throw the plane. The tubing acts like a big rubber band and pulls the plane into the air. Launch height is 50 - 200 meters depending on the wind. If you have a small launch field, you can get a short hi-start with only 8 meters of tubing and 25 meters of string.

Be sure to launch into the wind (with the wind blowing into your face). When you launch with the hi-start, throw the plane, don't simply let go. I've seen more planes crashed by not throwing than any other single cause. Assume the hi-start line will break just as you release the plane. The plane MUST be up to flying speed when you let go. Finally, don\Qt throw the plane at an angle. Throw it flat. The plane will rotate by itself as soon as you release it. This is easier than it sounds.

A normal launch on a hi-start triples the length of the surgical tubing. Beginners should launch with no more than double the relaxed length. After you get a little experience you should put more tension on the hi-start by backing up further. Do this slowly. Stop when A) the plane takes off with all the excitement you can handle or B) the surgical tubing is 4x it's relaxed length. i.e. if you have 25 ft. of tubing don't stretch it to more than 100 feet (75 feet of stretch). [1]

3.4.2 Winches

3.5 Hand launch

Hand launch planes are great for learning how to find and ride thermals. Unfortunately most flights are less than two mistakes high, so they are not for beginners. For those who already feel comfortable with flying larger planes, some suggestions are offered on hand-launch planes.

[Regarding finger holds] I've tried a finger hole near the CG, a finger hole near the wing trailing edge and a peg through the fuselage near the wing trailing edge. The peg has been my favorite. I used a 1/4 inch dowel that went through the Kevlar fuselage sides, protruding about 3/8 inch on each side of the fuse. It doubles as the rear servo mount (two servos in tandem). I faired it in with a 1 inch long triangle of 1/4 inch balsa, which also helps spread the loads to the center servo mount.

To throw, I use a two-finger grip (middle and pointer fingers with the fuse between them) and rest my fingertips on the peg. DON'T hook your fingers over the peg!

I'm sure that finger holds are a very personal choice. I like the peg in part because I flew a lot of Free Flight HLG, which uses a similar finger rest built into the wing trailing edge. YMMV. Some of my flying buddies have thrown my plane and don't like the feel at all.[24]

Whatever type of throwing "thing" you use, start with [the hole/peg] 2/3 aft from LE as a location, and go from there, it will definitely be in the ballpark. Some people throw from 2/3 fwd from TE, some from the TE, but never seen anyone outside of that range, so the middle (2/3 aft from LE) will be a good starting location.

Holes, no holes, or throwing sticks border on religion.[47]

The question of how best to obtain good launch height was recently E mailed to me, it prompted a bit of a narrative that seems appropriate to share with the exchange. I apologize if there have been previous threads on the subject, but I hadn't noticed any, at least for quite a while. Hope this provides some "usable" ideas on the subject. PLEASE note that I do not have a PHD in physical medicine or the like, but through lots of practice and trying many techniques have managed to come up with a non-painful method of obtaining good launches that I hope some folks find helpful!

About hand-launching Monarchs: The single most important thing is your FOLLOW-THROUGH!!! The longer you can keep your fingers on the ship, accelerating the whole time, the higher it will launch! Technique is really the biggest factor in launch height. I'm told that my launches are at least as high as the highest in our area, with a 9.5 ounce Monarch "C"! Of course, I really can't tell being underneath the thing, but Don and a lot of other folks have told me as much. What the heck--I'll gladly take their word for it!

Anyway, my grip on the fuselage is such that the forward bottom part of the fuse is flat in the palm of my hand. This feels a little weird at first, but what this position does is place your wrist in a "rearward bent" position prior to and during launch. This means that as you progress with the throwing motion, your wrist has more movement ("travel") from start to finish, giving you more "contact" time (and muscle) to accelerate the ship forward and up. It is a subtle little method that a lot of people overlook, but it DOES add power to the launch by employing more of your wrist strength. Holding the fuselage by your fingertips during launch robs you of much of this advantage. Try it!

Next, it is important to get your whole body into the launch (I know that sounds like one of those RIDICULOUS workout videos, but it really isn't THAT extreme-I wouldn't do it if it was!). The simplest way I can describe it is that you do NOT want to be FACING IN THE DIRECTION YOU INTEND TO THROW!!! If you face the direction you intend to throw, you lose all the power that the simple act of rotating your body has to offer! This can amount to a huge loss of power, and a big increase in pain! It forces you to obtain most of your power from your shoulder and elbow. I was launching this way when I first got into handlaunch, and nearly gave it up because I REALLY dislike PAIN. Practice facing 90 degrees from the direction you are throwing, and rotating your body in the direction of your throw as you move your arm forward in the throw (just remember to take a look in the sky before you throw; mid-airs at launch speeds are spectacular!). This takes an incredible amount of "load" off of your shoulder and elbow, while assisting in the acceleration (there's that word again) of the ship through the throw. When I finally figured this out, I found I could launch all day with no problem! Hand launch gliders got a whole lot more fun after this!

Finally, I find it helpful to keep your throwing arm extended (elbow straight or nearly so) at the start of the throw. This serves the purpose of allowing you a maximum amount of contact time/total travel during the launch, which gives you basically the same advantage as the wrist thing mentioned earlier--longer follow through; more acceleration!

If you think about it, big league pitchers, tennis players, and javelin throwers employ some of the methods I've attempted to describe, but HLG's require a blend of special techniques that are best developed by----- PRACTICE!!!!!.[48]

3.6 Estimating distance

I have obtained a simple rough estimate of height (actually, distance) by using the little metal "button" on the end of the transmitter antenna as an "aperture". Move the transmitter until the button is lined up between your eye and the plane and estimate the relative size of the button and the plane. The button is about the right size to be useful as a reference dimension. For example, if a 2-m (78 in.) plane is one-half "buttons wide", the button is 1/4 inch in diameter, and the antenna tip is 30 inches from your eye, then the ratios place the plane at about 1500 feet distance. (Altitude estimates need some information on angle to the plane as well.) What is nice is that you don't have to take your hands off the transmitter or your eyes off the plane. To obtain a handy reference height, measure the size of your button (or glue on a button of useful size) and the distance from eye to antenna tip in the position you would normally hold the transmitter. Then calculate this reference height. Of course, this height estimate can only be done if you do not have a frequency flag hanging on the tip of the antenna.[39]

4.0 Slope soaring

4.1 The plane

Slope ships are generally smaller and more aerobatic than thermal duration ships. Thermal ships will work on the slope, but they turn slower and lack the exhilaration of slope ships. Using them for combat is highly discouraged. On the other hand, a thermal ship can fly in much weaker slope lift than a slope ship. I would recommend flying your thermal ship a few times on the slope. If you like it, buy a slope ship.

Some recommendations for slope ships:

Go for a foamie! Two that come to mind are the Apex, 48" span and the Visionary at 64". Both are excellent for getting over the hump, learning curve wise. Add to that they are quick to build, and very crash resistant. Transporting the Visionary can be a problem as it's all one piece. Best to take some measurements first...[11]

For those out there who roll up their eyes at the very mention of flying wings (I was one of them) check this out...We fly a LOT of slope combat, with mostly various foamies, as we count "KILLS" only when the opponents plane hits the slope. Recently a new flying wing, the "ZAGI" has become far and away the most popular. Three reasons-(1) Performance-it flies great, is aerobatic and very forgiving, it is so easy to fly it lets you look for the enemy more actively instead of just flying the plane-and will pull off wild "HI-G" maneuvers with ease. It also has a certain entertainment value, as it does fly differently than a "real" plane, but is fun when you accept it's foibles. (2)Toughness-it is as nearly indestructible as anything I have seen, when I recover mine, I heave it back up on top our hill by throwing it like a boomerang, then hike back up. We throw them out upside down, spin them out frisbee style, whatever-no worries. (3)Cheap-quick-easy, "kit" consists of wire-cut foam wings, roll of tape, elevons, pushrods. Glue halves, wrap with tape, stuff in radio-FLY. The point of this rambling monolog is that wings CAN be worthwhile, and don't need to be as big a hassle as I have read about in RCSE recently. BTW if anyone wants a ZAGI, call MCLEAN'S MODELS at (714)363-7331, but I don't know if he has any left, he just makes racing and scale planes, and was selling ZAGIs for a friend of his in the California Slope Racers club.[12]

4.2 The lift

Ridge or slope lift is created when the wind hits a ground obstruction and is deflected upwards over it. For example, if the wind is blowing over the ocean and hits a 100 ft. high cliff above the beach the air will be deflected upward and (possibly) around the cliff. If you are standing at the top of the cliff and throw your plane toward the ocean, the air going upward over the cliff will lift your plane.

4.3 The ideal flying site

The perfect slope soaring site is a Devil's tower in Wyoming. You want a large bump that sticks up over 100 feet above flat terrain. The terrain should not have any trees or other obstacles to slow the wind down. If the bump is round you can fly no matter which direction the wind comes from. The top of the bump will be covered with grass for smooth landings. Your house is up there so you can fly whenever you want to.

Ok, you're not going to find a site that good, but there are a few really excellent sites and many good ones. Most sites only work well when the wind is blowing from a certain direction. The wind should blow perpendicular to the slope within +/- 45 degrees. Look for steep slopes at least 15 feet above the surrounding terrain. The slope and surrounding terrain should have a minimum of vegetation to disrupt the wind for at least one-quarter mile upwind. Small boulders such as rip-rap will not significantly affect the air flow. The slope area should be at least 100 feet wide. The top should be wide enough to land on (about 15 feet), and smooth enough to not rip your plane up. You should have reasonable access to the top. "U" or "V" shaped notches in hillsides work well to funnel the wind. The more you can exceed these requirements, the better.

4.4 Launching

For a Spirit, you will need 10 - 15 MPH winds. As you gain experience with the site you may find you don't need as much. A Spirit can handle up to about 25 MPH if you add ballast. To launch, aim the plane straight into the wind with a 10 degree down angle on the nose. Throw the plane straight and hard. You want it to be up to flying speed by the time it leaves your hand. Trim and stick positions should be neutral on launch. The plane should slowly descend below you, picking up speed. Let the plane fly about 40 feet away and gradually turn the plane left or right and run parallel to the face of your slope. As your speed picks up, nudge the nose up a little and your plane should climb slowly. Run the plane down to near the end of the slope and turn INTO the wind to make a 180 degree turn. Bring the plane back in front of you and down to the opposite end of the slope. Again, make a 180 degree turn INTO the wind. By now the plane should be well above you. NEVER, EVER turn downwind when slope soaring. Experiment with moving closer to or farther away from the slope. If the wind is not coming straight into the slope you may find one end lifts better than the other. When you want to land, let the wind blow the plane back over your head (but not behind you). If the wind is blowing at exactly your air speed, you can make a vertical landing. Note that as the plane gets close to the ground you will enter the ground effect and the plane will appear to speed up. Do not allow the plane to get downwind of the slope. A rotor will exist on the lee side of the slope. If your plane gets into it, you will have a very difficult time avoiding a crash.[1]

5.0 Improving your skills

The following discussion refers primarily to thermal duration flying. Though I have done some slope soaring, I haven't done enough to feel qualified offering more than basic advice in that area. Perhaps a hot shot slope pilot would care to contribute their thoughts...

5.1 Flight plan

Thermals drift with the wind. They tend to form repeatedly at the same location. These facts can be used to increase the likelihood of you keeping your plane up. In order to use these facts you must form a flight plan prior to launch. The flight plan will be designed to maximize your chances of intercepting a thermal. Consider a very simple flight plan. After releasing the towline you fly straight upwind until you are at half your launch height, then turn around and come straight back. With this plan, half you air time is wasted. The air you flew back in is exactly the same air you flew out in. Since there was no lift on the way out, you know there will be no lift on the way back. Consider a different flight plan. After releasing the towline you turn the plane 45 degrees to the right and fly straight until you are at two-thirds your launch height. You then turn 90 degrees left and fly until you are at one-third of launch height. You then turn your plane 135 degrees left and head straight back. With this plan, your plane was always flying through new air. Your chances of intercepting a thermal are dramatically increased. You will want to customize your flight plan to the site and conditions your flying at. If there is an area that frequently creates thermals, you'll want to make sure it is part of your flight plan. If you see other planes sinking in an area, make sure that is out of your flight plan. Don't launch your plane until you have a flight plan in mind, but don't be afraid to abandon it if conditions warrant.

5.2 Turns

Beginners seem to have terrible problems with turns. I believe there are two reasons for this. 1) Beginners over control the plane, 2) They don't understand the details of how the plane turns. Lets look at how a polyhedral plane turns in detail. The pilot pushes the control stick to the left. The rudder deflects to the left. This causes the plane to yaw so the right wing is ahead of the left wing in the air stream. Because of the yaw some of the air hitting the right wing tip is pushing on the bottom of it instead of just on the leading edge. That air is deflected downward, and by Newton's second law, the wing tip is pushed upward. This causes the plane to bank to the left. We are nearly one second into the turn at this point. Think about how the wing applies an upward force on the plane. When the plane is flying level, all the force is used to hold the plane up. Now that the plane is banked, part of the force continues to hold the plane up, but part of it now pushes the plane to the left. The plane begins to turn. Because part of the lift generated by the wing is now being used to turn the plane, there is less available to hold the plane up. The plane begins to sink noticeably faster. As it does it picks up speed, generating more lift until the amount of lift equals the weight of the plane. At this point the plane reaches about a 25 degree bank angle and the pilot returns the rudder to neutral. The plane continues to turn, but the bank angle begins to reduce because the left wing tip is more nearly level than the right wing tip. This causes it to generate more lift and raise the left wing tip. As the wings flatten out, the lift that was turning the plane is applied to lifting the plane. At this point the plane has not slowed significantly, so the lift exceeds the weight of the plane and it begins to climb, nearly making it back to the altitude it started at.

The typical beginner turn works slightly differently. Because of the delay between pushing on the stick and the plane beginning to bank, the beginner thinks nothing is happening and continues to push the stick to the gimbal stop. As the plane begins to sink faster due to the banked wings the pilot unconsciously pulls back on the stick to maintain the same speed. This tightens the turn and slows down the plane. The inner (left) wing is now traveling too slowly and tip stalls. Because a stalled wing generates little lift, the plane begins falling. This causes the plane to speed up and un-stall the wing tip. Meanwhile the plane has lost fifty feet.

When you are turning your plane recognize that it takes a little while to start and stop a turn. Anticipate this and don't over control. Know that the plane will lose a little altitude during the turn, but will get most of it back when you exit the turn. You don't need to use the elevator to slow down. Practice making S-turns until you can make smooth turns with little altitude loss.

5.3 Circles

Once you find a thermal, what do you do with it? Of course, you circle in it. Hopefully you will find many thermals and thus spend a lot of time circling. It makes sense to be good at it. The key here is to make sure you turns describe a circle relative to the air, not relative to the ground. Ignore the planes position relative to the ground. Begin a turn and maintain a constant bank angle throughout. Try tightening or opening the turn up. Practice entering and exiting the circle smoothly.

5.4 Thermal clues

Thermals are invisible, so how do you find them? There are several ways. The best is to look for another flyer already in a thermal. Note that hawks and other birds fall into the `flyer' category. When a thermal breaks loose from the ground air rushes in to replace the blob of air that started moving up. If this happens nearby you will feel a sudden change in wind direction. Use this information to modify your search pattern. You will be most able to sense the wind changes on your bare skin, so fly naked! When a thermal lifts off, it sometimes lifts dust and insects into the air. Any birds in the air will swoop down on the insects. If you see birds whipping around near the ground, try flying over them. You may find the thermal. Use your nose. If you can smell the horse barn half a mile upwind you know there are no thermals in that direction. A thermal would lift the scent away.

5.5 Landing

For sport flying landing is simply what you do at the end of a flight. For contest flying, you need to land at an exact spot at exactly the right time. In order to do this repeatably, most contest flyers develop a landing pattern. The details of the pattern will vary depending on your skills, your plane, and obstacles (i.e. trees), but most patterns are pretty standard. With the wind hitting your right shoulder, and the landing pin 25 feet off your left shoulder, make the downwind leg of your box pattern. The plane will pass right to left 100 feet ahead of you and 40 feet high. It is 40 seconds until landing. Fly downwind for 70 feet and turn left 90 degrees. Hold this course for 100 feet and turn left 90 degrees. The plane is now about 15 feet high, 45 feet from the pin and headed straight for it. Adjust your glide to pass about a foot over the pin. When the plane is about five feet short of the pin open full spoilers. The plane will hit the ground a couple feet short of the pin and slide to a 100 point landing. If the wind is blowing hard you will want to reduce your downwind leg. If it is very gusty you may want to come in a little higher and faster to maintain airspeed and control. If you find yourself a little late, you can cut the corners a little. If you are early you can stretch the corners out a little. [1]

6.0 Tools

6.1 Necessities

The following list of tools is pretty much required to construct a built-up model glider from a kit. If your budget is not so tight, you would do well to buy some additional tools from the next section.

Exacto knife or single edge razor blades - For cutting, whittling, etc.

Exacto Razor saw - For cutting heavier woods like spruce.

Thin CA - For gluing most anything (especially fingers!).

Five minute epoxy - When you need a slow bond.

Thirty minute epoxy - When you need a really slow bond (joiner boxes).

Clothespins converted to clamps - Remove each stick and put it back into the spring so the flat sides are adjacent. Useful for many clamping chores.

Wax paper - Epoxy and CA will not bond to this. Use it to protect things.

Baking soda - Great for filling gaps when used with CA. See section 2.6.1

Pencil - You get to figure this one out.

Selection of small screwdrivers - For attaching control horns, etc.

Rubber bands - More clamping devices.

Needle-nose pliers - Almost as useful as the Exacto knife.

Sandpaper & t-stock sanding bar - Makes a great sanding block.

Vasoline - Prevents gluing, also lubricates joints.

T-pins - For holding your plane down during construction.

2" wide tape - Use your imagination. Also good for patching holes in Monokote.

6.2 The well equipped workshop

Dremel tool w/attachments - Once you start using this, you'll wonder how you got by without it.

Set of small files - For trimming to an exact fit.

6" steel ruler - Great for measuring lengths as well as measuring out baking soda.

Masking tape - For writing on or taping where you want to remove the tape later.

[The ideal workshop] Lots and lots and lots of electrical outlets. Never enough. Don't need many circuits, just lots of places to plug in. Where you are going to put your work bench, put the plugs low, and build the bench with receptacles at the front, so that your Dremel tool cord doesn't pull your new model onto the floor. Just plug your bench into a receptacle.

Lots of light. Probably 4 4-foot 2-lamp fixtures with Daylight or Full Spectrum lamps should be close. The Daylight and Full Spectrum lamps will give a more realistic view of colors, as compared to sunlight. Cool White (the common lamp color) can give some strange results when you get the model outside. Check with the cosmetics dept. of a dept. store for horror stories of mismatching makeup or clothes before these colors of lamps were available.

Put the fixtures near the bench near the wall, otherwise you will be working in your own shadow all the time. Paint the walls and ceiling with *gloss* white paint to reflect as much light as possible. No use letting it absorb into the walls where it doesn't do any good.

Consider a large (4' x 8') bench in the middle of the room. A friend of mine did that, and it seemed very handy. He could have a wing going on one side, and a fuselage going on the other side, with supplies & tools in the middle. He used a sheet of sign makers plywood as a surface---it has a finished primed surface that is dead flat. A little pricey, but beautiful to work on. He built the framework underneath with 2X6 lumber to support the surface, and put a 1/2" ply shelf on the braces underneath.[13]

For a building surface, I currently use a large 1" (they also make thicker...) piece of dense particle board and I support it every 18" with a 4x4. This gives me a sturdy table. In a small shop I built in my cabin, I used a left-over 2x6x24" glue lam beam. This gives about the most sturdy building table I have ever seen. I have a left over 20 foot piece for my new shop...

For a pinning board, I have used with great success those dropped ceiling panels as are used in large office buildings. I use the large size which are 2x4 feet and can be found with a smooth white finished side. They come in 10 packs for about $15 and as such can easily be replaced. One of my friends uses the same ceiling panels and has built his bench so that one drops in and provides a much larger area around the pinning area for added support. I like being able to throw one away after it's truly cut-up...

If you do any vac-bagging, a big key is to make sure the table is absolutely level![40]

6.3 Field box

Your field box is a workshop with a handle. It will hold your transmitter, all the stuff you need to put your plane together, and a selection of tools and supplies for quick field repairs. You might even put your lunch in it.

Buy a fishing tackle box or toolbox. It should be large enough to put your transmitter in. Lots of drawers or subdividers is an advantage. Add all of the small tools from the `necessities' list. Also, add:

Plastic grocery bag - to put over your transmitter when it starts to rain.

Sun blocker - `Cause sunburns hurt.

I'd add double-sided servo tape. Handy for lots of things -- servos, mounting wings after a rear hold-down bolt breaks (don't ask)...

6.4 Altimeter watches

7.0 Materials & construction techniques

7.1 Glues

There are four types of glue commonly used in building model planes. Each has advantages and disadvantages.

7.1.1 Aliphatic glues

These are organically derived glues. Elmer's or Titebond glue are common examples. They are sometimes used in model building, but typically take several hours to harden.

7.1.2 CA

Cyanoacrylate. This instant glue was originally developed to bond skin after injury/surgery. It does that really well. It also bonds balsa wood really well. For that matter, there isn't much this stuff won't bond to. CA comes in several types:

Thin - Very low viscosity, cures in 5 - 15 seconds. This is what you will use most of the time.

Thick- High viscosity, Cures in 30 - 120 seconds. Good for filling gaps, but baking soda works better.

Foam friendly - Does not attack foam. Most CAs will dissolve foam. This stuff doesn't. Takes a little longer to cure.

Odorless - Has no unpleasant odor. Takes a little longer to cure.

For those with type-A personalities, there is an accelerator that can be sprayed on CA which causes it to cure instantly - when five seconds isn't fast enough. Kicked CA will bubble and get very hot. The resulting bond will be weaker than an un-kicked bond.

CA must be stored with some care. Failure to do so causes the nozzle to clog and the CA to harden prematurely. Before closing up a bottle, look through the translucent nozzle and knock any drops of CA back into the bottle. Gently squeeze out some air to confirm the nozzle is empty. Put the cap back on and store it in the freezer. (It has been suggested that storage in the freezer is a bad idea because of the condensation of moisture from the air inside the bottle. I don't know about other areas, but it works well in dry Colorado.) Don't buy the 2 ounce bottles unless you plan on using it quickly. They will usually harden before you finish them. Health concerns

Remember that CA was designed to glue your skin. That includes eyes, lips, etc. It can burn you if it cures quickly. There is no way to remove it from fabric (except with a knife/scissors). Handle with care. I've not heard of any specific problems associated with breathing the vapors, but I can't believe it does you any good. Work in well ventilated spaces and try not to breath the vapors.[1]

7.1.3 Epoxy

Epoxy is created by combining a resin and hardener. Once mixed the compound cures and hardens. Hardened epoxy creates an incredibly tough bond. The bond will tolerate more flexing than CA, though it becomes more brittle with age. When you buy epoxy you will find several varieties. The most common are 5 minute, 30 minute, and 2 hour epoxy. Most are mixed in a one-to-one ratio but other ratios and times are available. The times listed are the working time of the epoxy - how long you can push it around before it gets too hard to work with. The time before you can handle your new construct is typically triple the working time. The time before you the epoxy reaches 90% of its final strength is about ten times the working time. Low temperatures and high humidity can substantially extend these times.

Use 5-minute epoxy in those situations where CA does not give you enough time to position the components being bonded. Use 30 minute or 2 hour epoxy for wing joiner boxes. Use 2 hour (or longer) epoxy on bagged composite wings. In general, the longer it takes the epoxy to cure, the stronger the resulting bond will be. Epoxy has a very long shelf life, but takes longer to cure the older it is.[1] Health concerns

The latest issue of Epoxyworks (Gougeon Brothers, West Systems) had the following warning:

"if used to clean epoxy from your skin, vinegar can promote overexposure to epoxy and subsequent allergic reactions. Common household vinegars, both distilled white and apple cider, contain 4 to 10% dilute acetic acid. They also contain low percentages of alcohols and mineral salts. When applied to remove epoxy, vinegar slightly dissolves it then penetrates the protective layers of skin, carrying epoxy into your subdermal tissues. This increases the chance of an allergic reaction, and may also increase the reaction's intensity. Any wiping, rubbing or agitation of the contact area will likely worsen the situation.

"You can safely use vinegar to clean your tools. You might also use it occasionally to get epoxy off of your skin without much risk of health problems. You'll further reduce the risk by gently washing with soap and warm water after using vinegar this way.

"However, you shouldn't use vinegar to clean epoxy from your skin on a regular basis. It's much safer to use a waterless skin cleanser or other detergent-based products with a strong emulsifying action. These won't drive epoxy into your sensitive subdermal tissues.

"Working clean and wearing protective clothing, such as gloves and long sleeves, is the best way to reduce the need to expose your skin to any cleaning agent in the first place."

Epoxyworks mentioned you can subscribe by filling out the subscription form at the web site-- http:/www.cris.com/~gougeon.

7.1.4 Other

Various other `glues' are sometimes used with model building. Beware of RTV which releases a gas that attacks electrical connections and components.

I use a glue very similar to Shoe Goo with great success: This is the Pacer Zappa-Dappa-Goo. Its the same thing, I think, except that I think Pacer puts more solvent in it (smells like MEK) It works great for putting in pushrod cables, and servo trays. My Shoe Goo dried in the tube, so I had to pay hobby-shop prices. I planted my new Ron Vann Laser after failure testing a carbon-fiber wing-rod last Saturday. This "spot landing" was one where I had to use a spade to dig out the safety nose, but the servos and cable housings stayed intact. The flexibility is also greatly appreciated when the fuselage expands and contracts at different rates depending on the different materials used in the composite matrix. (Technobabble for the fiberglass getting longer slower than the pushrod tube)

I know others who use silicone sealers with luck, but the Goo types of glues are easier to manage because they are easily thinned. The flexibility makes it really easy for putting in the tail-posts, tow-hook block, and other wooden pieces.[14]

In response to your query regarding "GOO", there are a number of brand names for basically the same product. "Shoe Goo" is one of the more popular brands. It is marketed for use in repairing worn out tennis shoe soles. The particular product that I use (because it is available in our large discount hardware stores such as HomeBase, Home Depot, etc.) is "GOOP". It comes in a tube and is available in different strengths (i.e. Household, Industrial). I am using the Household Goop. GOOP is manufactured by ECLECTRIC PRODUCTS, INC. of Carson, California.

The label says it contains "Tetrachloroethylene". I have no idea whether or not that is the base ingredient. I only know that it works.[6]

7.2 Woods

Several types of wood are used in constructing model planes. The following items were posted on RCSE.

Balsa has a high strength to weight to COST ratio. The strength to weight ratio of balsa is one of the worst of any of the materials commonly used in model building. Some median values for strength to weight for materials are:

Strength to weight of various materials









Kevlar in Epoxy


Uni S-gass in Epoxy


Uni Carbon in Epoxy


(Note that these are all relative strengths in comparison to Carbon)

The good thing about balsa is that the size of the member that you have to use to get adequate strength usually will be thick or stout enough to avert slenderness or buckling problems.

7.3 Fiberglass, Carbon Fiber & Kevlar

These three man-made materials are frequently used in more advanced sailplanes. They are always held in place with epoxy. Some excerpts from RCSE:

<Anyone built a carbon or carbon reinforced fuselage and then put the Rx

aerial inside the fuselage?> griff@vesta.chch.planet.co.nz


<A friend is making such a fuse' and would like to install aerial inside.>


Carbon is not radio transparent and it will act like a Faraday cage and reduce or eliminate the reception of the signal. I always take my aerial out close to the towhook and tape it along the bottom of the fuselage. Leave about 250 mm hanging loose so that if can flap around. On T-Tails it has been found to be a good idea to run the end of the aerial up the front of the fin on the outside, some have even extended the aerial to do this although this might entail a retuning on the aerial input.

From a structural viewpoint it is not really such a good idea to make a carbon fuselage. The old saying is that "if it don't bend it will break", to a large extent it is true for fuselages. Carbon makes a very stiff structure but stiff structures are susceptible to shock loads such as hard landings, they can shatter. So to make them strong enough you need to use more material than is really necessary for the flight loads. It is far better to use carbon for stiffening specific areas such as openings.

A better plan is to use Kevlar or any good Aramid material combined with an inner and outer layer of thin glass cloth to allow post mold finishing. It is radio transparent. Kevlar has great shock loading capabilities when combined with a good Epoxy laminating resin. Do not use polyester it is too brittle to accept the flexures that occur when landing. A kevlar fuselage is likely to be lighter than an equivalent strength carbon version if you are careful.

Cloth choice is everything, go for a very tightly woven thin cloth, the holes in a loose cloth have to be filled with resin and this is heavier. We have used a super material for fuselages but it is almost impossible to get outside of eastern Europe, this was called "Russian Kevlar" it is a chocolate brown colour when wetted out, very tightly woven and thin.

Another tip is to understand your materials. Kevlar is hygroscopic, so it tends to soak up atmospheric moisture. If you use a piece that has been lying around for some time it will have a significant moisture content. The trick is to cut your cloth to size for the mold and cook it at 100 degrees Centigrade for an hour or so. Use it within a couple of hours of cooking and it sucks up resin harder than a parched camel. It's even better if the cloth is hot as it goes into the mold. You need less resin and the wetting out is much more effective. If you have some scientific scales try weighing a piece of kevlar before and after cooking.

The other thing is to understand the stress paths in the molding and tailor your use of materials to cope with it, but that is a subject that would take a very long time to cover.[9]

I have been a bit undecided about the use of carbon in fuselages and going by the experiences for and against on the list, I felt it was time today to gain some experience. After programming the fail-safe, I took a receiver, battery and servo to the local fishing tackle shop and explained to the staff what I wanted to do. (They are used to me buying Berkley Stainless leader for foam cutting and other heavy duty connecting tackle and once expressed an interest in my winch for shark fishing from the jetty) With no antenna on the trusty Graupner MC20, I could walk about 50 metres before the fail-safe came on. (This rather impressed me, especially as 52 metres would have been the center of a main highway, and this was about 5:20pm on friday afternoon) I returned to the shop and stuffed the receiver antenna down the first carbon fishing rod blank I came to. As I went to walk out the door, not 2 metres from the transmitter, the fail-safe came on! I found 4 different blanks of mainly carbon content and tested each, with pretty much the same result. By now the other customers were wondering what the hell I was doing and were giving me strange looks. I also found that I could get fail-safe lockout with a rack of carbon rods between me and the transmitter. This appeared to be a very effective screen and there was a distinct line which I could cross and have lockout of signal. The rods were throwing a shadow, if you like, and in the shadow the receiver went to fail-safe instantly. There exists in our club, the opinion that carbon itself can act as an antenna. I think that although it is possible, I don't think it is likely and will seek to disprove this theory in the near future by testing a carbon tow antenna on my receiver. I will not be building any carbon fuselages in the near future. This is purely a basic test and is by no means conclusive. Many things about radio is still a mystery to everyone, but this has some pretty simple conclusions I will leave to the readers to draw for themselves.[41]

Torsional stiffness of a wing structure is critical for a flying wing. The designer of your aircraft is correct in suggesting fiberglass instead of kevlar.

Kevlar is a great material for most of our uses, its strength is very good. But, the problem (or advantage, depending on how you look at it) with kevlar is its relatively low elastic modulus. Compared to carbon fiber, kevlar will "stretch" more for a given load than carbon fiber. That's why kevlar structures are much more durable than carbon fiber or fiberglass structures. The fiberglass elastic modulus is not as good as carbon fiber, but it is better than kevlar.[15]

[Editors note] In the spring of 1996 a raging debate occurred on RCSE about the relative merits of Kevlar and fiberglass fuselages. Frank Weston (WACO) performed the following experiment.

The purpose of this test was to determine which material is superior for construction of open size sailplane fuselages.

Two WACO BETA fuselages were constructed. These fuselages were as close to identical as possible except one was constructed of 1.4 oz. plain weave glass, one of 1.7 oz. plain weave Kevlar. West System 105 resin and 206 hardener were used for both fuselages, and similar reinforcements and layup schedule were used for both fuselages. Both fuselages were tested at a weight of 3 oz. The length of the BETA fuselage is 49 inches.

The Torsion Test. A solid wooden plank was mounted to the fuselage at the normal wing mount position. This plank was then clamped securely to a work table. To counterbalance the weight of test apparatus at the tail, the nose of the fuselage was prevented from rotating about the pitch axis, but was free to rotate about the roll axis. A 15 inch lever arm was mounted at the normal tail position. Weights were suspended from this arm, and the amount of twist at the end of the lever was measured for each weight. Each fuselage was tested twice.


Torque in-oz. 37.5 75 112.5 150

avg glass twist 1.75 3.13 4.63 5.75

Kevlar twist 1.00 2.13 3.13 4

Conclusion: The glass fuselage twisted significantly more than the Kevlar

The Bend Test. Fuselages were suspended as for the torsion test. Weights were suspended from the tail, and the displacement downward of the tail was measured. Each fuselage was tested twice. Results:

Weight oz. 6 12 18 24 30

avg glass bend 0.25 0.57 0.9 1.13 1.38

avg Kevlar bend 0.13 0.25 0.5 0.75 0.88

Conclusion: The glass fuselage bent significantly more than the Kevlar

The Crush Test. Each fuselage was clamped firmly on it's side on the top of a solid work table. Weights were placed on the fuselage in the area of greatest diameter. The amount the fuselage crushed was measured.

Weight in oz. 64 128

glass crush 0.16 0.25

Kevlar crush 0.000 0.016

Conclusion: The glass fuselage was easier to crush than the Kevlar

The Crash Test. This test was conducted in two parts. For both parts, the fuselages were loaded with lead to simulate flying weight of about 52 ounces. 4 oz. was mounted in the v-tail position, 18 oz. was mounted internally, and 24 oz. were mounted to a spar which served as a wing. The fuselage CG was in the normal flying position.

For the first test, the fuselage was suspended at its CG from a tree limb about 20 feet high. The fuselage was suspended as a pendulum, and would strike the ground at an angle of approximately 30 degrees when released. The fuselage was released at about a 5 degree angle from true. Each fuselage was released at an arc distance of 1,2,3,4,5,6,7, and 8 feet, and each distance was tested five times. Results:

Neither fuselage suffered any damage.

Conclusion: Maryland sod is pretty soft this time of year, and it takes a pretty hard crash to damage a fuselage.

For the second test, the fuselages were dropped vertically onto a thick doormat over a concrete floor. Each fuselage was dropped five times from each height, starting at 6 inches and increasing in 6 inch increments. Each fuselage was dropped at a 5 degree angle from dead vertical. Results:

Neither fuselage suffered any damage until a height of two feet was reached. At two feet, on the fifth drop the glass fuselage suffered slight damage to the tail boom just forward of the V-tail. It was still flyable. On the first drop from 2.5 feet, the glass fuselage failed at the wing mount, and forward of the V-tail. It was un-flyable without repair. On the fifth drop from 2.5 feet, the Kevlar fuselage was closely examined. The only damage evident was a little crazing of the Kevlar/epoxy skin in the forward wing mount area. The test was ended, and the Kevlar fuselage is still flyable.

Conclusion: A Kevlar fuselage is more crash worthy than a glass one, particularly when landing vertically on carpeted concrete.

General Observations: It was obvious from the onset, that the glass fuselage would be no match for the Kevlar. Just handling the fuselages would be enough to convince an experienced pilot. The actual cost of the Kevlar fuselage is about $16 more in terms of time and material. The glass fuselage was more uncomfortable to construct due to fiberglass particles from sanding. WACO will continue to offer 100% Kevlar fuselages and carbon reinforced Kevlar fuselages. If a weight savings of 4 to 8 oz. in open size ships is significant to you, you might want to try a Kevlar fuselage.[16]

From a chart in the Aircraft Spruce & Specialty Co. catalog:

Construction characteristics of materials









Weight (density)
























impact resistance







7.4 Built up construction

Reply to: RE>[RCSE] What is the lightest cover

Weight tip #1 Do not use an iron on covering with adhesive on it. With an open structure wing you cary a lot of adhesive you will never use.

My personal preference is for transparent Micafilm from Coverite. Their white

should be lighter than the colors. You need to brush an adhesive onto the structure. I have had great results with Coverite's Balsarite, others recommend water soluble Balsaloc. Maybe I have just gotten so high with balsarite that I think I have done a good job. Micafilm is laminated film with thousands of little fibers that make it all but tear-proof. A stick or twig that might split monokote and create a long tear, will often only dent the Micafilm. It also takes paint well for markings.

Here are some numbers that float about from time to time.

From the article "Heat Shrinkable Coverings" by Lee Murray in the February 1988 issue of Model Aviation:

Covering characteristics






Weight (oz/1000 in2)

S. Monokote

Top Flite



Oriented Film


S. Monokote

Top Flite

Opaque Yellow


Oriented Film


S. Monokote

Top Flite

Trans. Orange


Oriented Film






Oriented Film


Black Baron




Oriented Film






Oriented Film




Opaque Red


Oriented Film




Opaque Yellow


Oriented Film




Trans. Red


Oriented Film


Indy RC film

Indy RC

Opaque Orange


Oriented Film



Opaque Red


Oriented Film















Top Flite









N/W Fibers






N/W Fibers/Film

0.8 using Balsarite


7.4.1 Advantages over composite construction

Built up planes are almost always less expensive than composite planes. Not only because of the cost of the materials in the plane, but because of the tools used to create it.

Repairing a built up plane is easier than repairing a composite plane. By the same token, it is easier to modify an existing built up than an existing composite.

7.5 Composite construction

There have been several answers to the question about foam wing reinforcement posted recently. They have all correctly stated the 'proper' way to reinforce the structure of a wing under bending loads.

However there has been a slight lack of attention to the exact mechanism of failure in sailplane wings. Premature wing failure usually can be divided into two categories: failure due to poor wing construction (poor bonding of structural components), and failure due to poor design.

The first mode can be eliminated by careful attention in the building process. Making sure that composite materials are thoroughly saturated by the matrix (epoxy) will create a MUCH stronger wing. Eliminating voids where main structural components interface is another good strategy. Skimping on the epoxy in critical areas can be disastrous.

The second major cause of premature wing failures is due to poor wing design. Stress risers such as servo holes and spar termination points are the cause of most of the wing failures that I have seen. A crack in an ideal material creates a stress concentration factor of about six. That is, the material is about six times weaker with a crack than without, depending on the crack size this stress concentration factor increases. This is basic 'Griffith's crack criterion' stuff. In our case we do not have ideal materials, and our loads are not uniform, so the intensity factor goes up even more! The moral is not to put any holes in the wing in the most critical areas. Don Edberg did an article several years ago where he found that the stress intensity goes down by about 200% after the first 13 inches out from the root. This is the MOST critical area of the wing DON'T PUT ANY HOLES IN THE FIRST FOOT OF WING! And don't even think about ending a spar there!

A final area worth addressing is the nitty gritty of a wing failure. When a beam (wing) bends, the top is under compression and the bottom is under tension. The result is a shear stress. The wing skin/core/spar interface is the location of almost all wing failures. It is very rare to have a spar then skin fail. The shear at the interface will usually manifest in a failure of the foam core surface. The foam is much weaker in shear than the skin, thus it is the foam that fails resulting in a delam-fold. This is the case in a stressed wing structure. In a spar system, the spar/reinforcement/skin interface is critical. The reinforcement must be an integral part of the spar. The failure mode is usually at the reinforcement-spar interface. The spar material (wood or composite) is usually weaker in shear than the skin or reinforcement or bonding material. Thus like the stressed wing example the weakest link fails, resulting in a fold. So the solution is to reinforce the weakest part of the wing.

The big thing to remember is to reduce the number of stress risers. Reinforce the top surface more than the bottom. I have always seen wings fold on tow, rarely while performing a negative-G maneuver. And make darned sure that the reinforcement is part of the spar, not slightly off to the side or accidentally not glued to the spar.

I am about to start building a wing for a competition XC glider for a friend who is short on building time right now. The wing span is about 150" and will be constructed in three sections. The airfoil will be a 7012. Root chord is about 11". The foam cores have been cut assuming a 1/16" balsa skin. For ease of construction I would like to build the main panel without a traditional fully penetrating wood spar, using glass and CF beneath the balsa skin for strength.

My current plan is:

Wing Top:

1) a diamond of unidirectional CF, about 4" wide at the root, tapering to about 1" at each end of the panel (centered on the 25% MAC)

2) a diamond of bias weave glass, about 6" wide at the root, tapering to a point about 3/4 of the distance from the root to the end of the panel in each direction (centered on the 25% MAC)

3) a diamond of straight weave glass, about 10" wide at the root. tapering to a point about 1/2 the distance from the root to the end of the panel in each direction.

Wing Bottom:

1) a diamond of unidirectional CF, about 3" wide at the root, tapering to about 1" at each end of the panel (centered on the 25% MAC)

2) a diamond of bias weave glass, about 4" wide at the root, tapering to a point about 3/4 of the distance from the root to the end of the panel in each direction (centered on the 25% MAC)

3) a diamond of straight weave glass, about 10" wide at the root. tapering to a point about 1/2 the distance from the root to the end of the panel in each direction.

The tip panels will be joined with a short brass tube and wing rod with some glass reinforcement on top and bottom of the joiner box.

This layup is based on SWAG's and TLAR! Is this too much? Is this not enough? Does anyone have experience with this sort of layup on anything larger than a HLG or sloper? I would appreciate and comments, suggestions, equations, etc. to design this.[19]

I build XC ships to withstand nuclear attack, but by just about any building standards your proposed layup is way under built. The tip panel joiner system should be about as strong as a "medium strong" (11/32" steel) joiner on a 100" plane. With no spar you need blue foam or (better) spyder foam. With CF over blue foam, the following center section layup is probably strong enough. Note: CF weight is about 5 oz./yard.

All over: 1 layer CF + 3/4 oz. skin coat glass.

Doubler: 4' wide (2' each side), full chord: 1 layer CF (taper the last foot)

Tripler: 2' wide (1' each side), full chord: 1 layer CF (taper the last 6")

4-pler: 1' wide (6" each side), full chord: 1 layer CF (taper the last 3")

The layup above is strong enough if everything goes well. A manufacturing defect (a gap between two core panels) caused a spectacular foldup on a very hard launch. I don't think the overbuild is greater than a factor of 2.

The 1/16" balsa might have 1/2 the strength of 5 oz. CF (less absolute strength by far, but thicker and resistant to buckling failure). You could probably run a lighter layup of CF (3 oz. instead of 5 oz.) with the balsa skin, but the blue foam or better is mandatory.

BTW, for doublers, etc., don't center them up at 25% of the MAC. Center them over the fat point of the airfoil where they will do the most good.

XC planes take quite a beating way up there. In my experience, about half the new planes that get trotted out with pride on contest day go home in a bag after vaporizing at altitude. Be one of the other half.[20]

>Does anyone out there have any idea of what kind of layup to use on a (light, <2 oz.) hand launch fuselage. I'll be using the lost foam method. Also, since I heard that using acetone to dissolve the foam makes a sticky mess, I will probably use a dremel router. Any ideas on this. Thanks;

> Mike Ziaskas, San Diego


Don't worry about the "sticky mess". Any residue can be washed away with lacquer thinner.

I use a layup consisting of 4oz cloth, then 8 stripes of carbon tow (about 1/4" wide each), then 1.5 - 2oz kevlar.

Pre-preg the cloth by laying it out flat on waxed paper, applying epoxy with squeegee, then covering with more waxed paper and squeegeeing away as much epoxy as possible. This results in a high (near 50:50) glass:resin ratio. Peel away the top layer of waxed paper and use the bottom layer as a carrier sheet to position the cloth over the foam plug. Don't overlap the wrap more than about 1/4". Use a squeegee to press the cloth against the plug and keep the edges straight.

Lay the CF tow over the cloth spaced evenly around the circumference of the section. Then wet out and lay the kevlar outer layer similar to the cloth procedure. For a smooth finish, thin some epoxy about 30% with alcohol and add microballoons until an enamel-paint consistency results (LOTS of microballons). Paint it on (it'll want to sag, so keep rotating and brushing it until the alcohol flashes off). Then sand until you just barely see fabric.

You won't get to 2 oz., but 3oz is achievable.[21]

Dean Morris wrote:

>1) Is this type of composite construction the exclusive domain of blue, gray, and spider-foam, or can white foam be used effectively? <

White foam can be used quite effectively for most types of ship. I have built ships ranging from a 13 oz. chuckies right up to 3m F3J ships using glass over white foam. You do have to be careful about the amount of vacuum you use, and also the thickness of mylar. Too much vacuum or mylar which is too thin will result in slightly wavy (bumpy) surfaces, due to the bead structure, and inconsistencies in foam density. Due to the lower density, you have to be very careful when installing spars, etc., to avoid "hangar rash" on the cores. Chuckies will be fine with 16 kg/sq.m foam (1 lb, I think), but larger ships need 24kg (1.5lb) or even 32 kg(2 lb).

>2)In the case of Blue & Spider foam, is it really necessary to have a vacuum pump capable of 18" of vacuum, or is my "aquarium" pump capable of "getting the job done"? <

A smaller pump should be adequate for blue foam. Do a dry run using only a wing core with mylar and breather, and see if the mylar pulls down tightly over the LE of the wing. If it does that reasonably well, you should be OK. (btw I use 0.25 mm mylar.)

>3) Can someone please provide me with an idea of what weight of fiberglass to use on HLG, 2-meter, and 3 meter size wings <

This is a difficult one. It depends on what foam you're using, what kind of durability you want, etc. A few examples: Chuckie wings (1.5m span), 16 kg(1 lb) white foam, 2 tows of 12K carbon tow spar - 2 layers of 1 oz., (1 at 0 degrees, 1 at 45 degrees). 3 meter (F3J), 3 piece wing (very light layup): - 24 kg white foam, strong CF spar system, centre panel has 2 layers 3 oz. (1 at 0 deg. 1 at 45 deg) + 1 layer 1oz (pinhole control). Tips are 1 layer 3 oz. + 1 layer 1 oz.

>4) What are the primary advantages/disadvantages of this type of construction over that of balsa or Obechi sheeted wings? <

IMHO - advantages: time, cost, less finishing work, lower weight (esp. on chuckies). disadvantages: I'll let you know when I find some;-)

7.5.1 Advantages over built up construction

7.6 Wing incidence

>I am trying to set up the incidence on the wings for my Shadow 120. This is a typical ARF with presheeted wings, wing rod hole and incidence hole pre-set in the wing, and the wing rod hole pre-drilled in fuse. My job is to drill two matching incidence holes in the fuse. I tried it once and it came out wrong. Yes, incidence is VERY important on 120 inch sailplanes since the thing had a hard roll tendency which was difficult to correct. I am trying to correct the situation and I am interested in some good hints on how the pro's set up these small holes.

>thanks for any help.



If you have one, a Robart incidence meter (glorified level) can be used for the job. Otherwise you can make a sighting jig that will do the job.

1) Take the wings (off the fuse) and a short piece of 1/2" tubing or dowel. Remove the incidence pins in the wing if possible.

2) Tape a 12" x 2" piece of thin cardboard, balsa, etc. to the wing root on each side. As much of the thin sheet should stick up above the wing as possible. You can cut some notches in the sheet to clear anything that will stick out of the wing.

3) Put the wings together on the tubing or dowel (if you can get the wings close together on the joiner rod you can use that).

4) Trim the top of the sheeting while the wing roots are correctly aligned. If everything up to this point is straight, the top edge of the sheeting will line up when the incidence in both wings is the same.

5) Install the wings on the fuse. Align the wings so that the root lines up with the "airfoiled" part of the fuselage. Don't worry, it won't. Just split the difference. (And yes, I know you can't see well because of the sheets. Tough.)

6) Sight across the top of the sheets to verify that the guy who carved the original plug for the fuselage needs a white tipped cane. Juggle things until the sheets are aligned and the biggest misalignment with the fuse is near the back and on the bottom (out of sight, out of mind).

7) Carefully mark the position of the wing. Fine pencil lines at several points are accurate enough for this job.

8) Rip everything off and decide who gets moved. If possible, hog out the holes in the root rib enough to allow the alignment pin to move enough. Then put in a blob of epoxy, slide everything back together and wiggle it 'till you're happy with the alignment. Wait for the glue to go off.

If you can't move the pin in the wing, just hog out the fuse holes and move the receiver tube.

9) Go fly.[20]

This may sound difficult, but it is very easy to get an exact match between wings every time. I have tried the Robart incidence meter, and I was not satisfied with the alignment. It was too dependent on the flap position, this is much less sensitive. I get much closer this way. I have used this on Synergy 91, Synergy III, Spectrum 2m, couple of home brew, and some Oly 650 (for my kids).

The easiest method that I have used to set wing incidence is the following:

Overview: Using 2 arrow shafts strapped to the wings (one per wing), using the arrow shafts as extensions of the mean chord of the wings, and then aligning the arrow shafts.

1) Set one wing with alignment pin hole drilled and the alignment pin epoxied into place. Use the wing saddle as a guide for getting it close. This wing is the reference and it's alignment is done. Now, on the other side, glue the alignment pin into the wing and drill out an oversized hole on the fuse approximately where the alignment pin will need to be. Remember, the alignment of the wing to the fuse is not as important as the alignment of the wings to each other (assuming that the wing / fuse alignment is close).

2) Get 2 fiberglass arrow shafts and 2 #64 rubber bands. If the flaps have already been cut out, then they need to be taped into place so that they will not move into a cambered or reflex position. Place the arrow shafts about 8" to 10" out from the root on the bottom of the wing so that there is about 1" to 2" of arrow shaft behind the flap and 10 to 15" of arrow shaft in the front. Use the #64 rubberbands over the top of the wing to strap the arrow shafts to the bottom of the wing. The arrow shaft should touch the bottom of the wing in 2 places. At the trailing edge and at the point of max thickness. If you need to lower the arrow shaft (because it touches the bottom of the wing at 3 or 4 points), cut 2 small hard balsa blocks, and using them at the trailing edge to shim the arrow shaft.

3) With the model resting on a table or some type of stand, you stand at the wing tip of the non-aligned wing and sight from the front tip of one arrow shaft to the front tip of the other. Twist the wing as necessary to align the arrow shafts at the tips. If they are perfectly aligned, you will be able to raise your point of view up a little and see the top edge of the second arrow shaft as a constant width from the leading edge of the wing to the tip of the arrows. If one arrow is up or down, then adjust the wing whose alignment pin has not been set. If necessary, make the hole in the fuse more oval in the direction that is needed.

4) When the alignment is to your satisfaction, pull the wing out far enough to grease the alignment pin with Vasoline and put a piece of masking tape over the hole in the fuse and another on the wing with the alignment pin sticking through. Poke out the masking tape on the fuse to the same as the oversized hole that you drilled out. Now mix up a batch of 5 min and add microballoons until it is nice and thick, and spoon it into the hole in the fuse. Now join the wings and RE-ALIGN to your satisfaction. This is the critical part. Now sand bag the wings in place (or hold the whole assemble if you are patient, but check the alignment every once and awhile), and when the epoxy is mostly set, pull the wings out.

Paul Clark, SKY PILOT ONE, from Osaka, Japan commented in Digest #488 on the importance of incidence to stability of RC sailplanes. Relative incidence of the wing and tail, and CG location are complimentary attributes which together control pitch stability. They have a chicken-egg relationship which cannot be broken.

First some definitions: Incidence refers to the angle between a flight surface and a somewhat arbitrary reference plane, typically called the "fuselage reference plane". This horizontal plane is usually set up so that it is level on the drafting board (or computer screen) in side view, and the fuselage is drawn over it. A boat analog is the water line. A positive incidence angle is always leading edge up.

Incidence angle may be specified in two ways. It is typical for modelers to specify what I call "geometric" incidence. This uses the chord line of the airfoil as the section reference line. The chord line connects the trailing and leading edges (line of maximum length). Alternatively, there is what I call "aerodynamic" incidence which uses the "zero lift line" as a section reference. When the angle between the zero lift line and the freestream air is zero (angle of attack = zero) there is zero lift. The zero lift line is above the chord line for positively cambered airfoils. A pretty good rule of thumb is that this angle is about one degree per percent camber. Thus the geometric angle of attack of a 3% camber airfoil at zero lift is about minus 3 degrees. The importance of this concept is that the effective incidence of different wings can be compared even if they have different airfoils.

Notice that I have slipped in half a definition of angle of attack. This is the angle between the section reference line and the flight path (in the case of wings) or between the section reference line and the local flow in the case of tails. Again, there is "geometric" and "aerodynamic" angles of attack. What is nice about aerodynamic angle of attack is that all wings (of similar aspect ratio) will make about the same lift coefficient at the same aerodynamic angle of attack. A pretty good rule of thumb is that the wing will make 0.1 Cl per degree of aerodynamic angle of attack.

The incidence of the wing controls only the angle of the fuselage in flight. The "deck angle" (there's that boat thing again) is the angle of the fuselage reference plane relative to the direction of flight. If a wing mounted at five degrees of aero incidence is trimmed to fly at a Cl of 0.5, then the deck angle will be about zero. If the aero incidence is zero, then the fuselage will be nose up with an angle of plus five degrees, and so on. Typically, wing incidence is set to give the lowest drag at the speed of interest.

Stabilizer incidence is set to trim (balance) the moments (torques) about the CG. These moments arise mostly from the wing pitching moment and the CG location compared to the wing aerodynamic center (typically taken as the quarter chord of the mean aerodynamic chord). What counts in setting tail incidence is the angle of the tail relative to the local airflow which is a function of wing angle of attack. So what really matters is the angle between the wing and tail, not the incidence of either one independently. This relative angle is called "decalage". For instance, a given setup might require that the tail be set at four degrees less incidence than the wing (four degrees of decalage). If the wing is set at four degrees, then the tail is set at zero. This plane will have a deck angle of about plus one degree at a Cl of 0.5. The same plane could be modified so that the wing has an incidence of 10 degrees in which case the tail would have to have an incidence of six degrees and the deck angle would be minus five degrees at a Cl of 0.5. (We're talking aerodynamic angles here.)

It is worth pointing out that moments generated by the wing and stabilizer both increase as the speed squared, but the moment generated by the center of gravity is constant (straight and level flight assumed).

A detailed discussion of CG location is beyond the scope of this note, but suffice it to say that there is a CG location, called the "Neutral Point", at which the aircraft is astable in straight and level flight. As the CG moves forward, pitch stability increases. The degree of stability is often specified by the distance of the CG is in front of the neutral point, in mean aerodynamic chords. This is called "static margin". A static margin of 0.2 Cmac is typical, although I'm sure many fly with less.

As the center of gravity moves forward with increasing stability, the download on the tail increases (or lift diminishes) so that it must have a greater negative angle of attack and less incidence.

So, perhaps it is clear (after all this) that increased pitch stability requires increased decalage to trim the forward CG. But it can be looked at from the opposite point of view as well: Increased decalage provides more stability, but it requires a forward CG to trim the airplane!

Decalage can be adjusted in several ways. The wing can be shimmed to adjust its incidence. The tail can be shimmed or adjusted as a whole to adjust incidence. Lastly, all the fixed surfaces can be left alone and the elevator can simply be retrimmed.

Perhaps this discussion also provides a better picture of pitch stability. If you imagine the tail balancing the nose weight you can see that at high speeds the tail wins and the plane pitches up. At low speeds the noseweight wins and the plane pitches down. As the CG moves aft and decalage is reduced this effect is diminished. When the CG reaches the neutral point, this effect is extinguished and the plane is astable.

Also, if decalage is reduced in flight, the plane must speed up until the tail can again balance the noseweight (down elevator trim increases speed). Conversely, increased decalage slows the plane down until stab down force again balances noseweight (up elevator trim decreases speed). [22]

7.7 Sheeting/covering wings

If you are building wings in which the flight loads are carried by spars, then by far the simplest way to apply sheeting, and also foolproof, is to use transfer tape. No clamping, weight, or vacuum is required. You just put the tape on one side of a wing core, then peel off the backing. Press the leading edge of the core against the sheeting. It will stick instantly. Then, take the whole thing, sheeting side down, and roll it slowly into the appropriate wing saddle so that the entire core is pressed firmly against the sheeting. Do that for both sides of each wing. It's best to do the bottom surface first. Then, trim the trailing edge and taper it properly so that the top sheeting will not have to bend where it encounters the bottom sheeting. Before applying the top sheeting, you will want to put transfer tape along the tapered portion of the trailing edge, as well as on the core. If you want to reinforce the trailing edge/control surfaces you can apply light (0.5 - 0.75 oz.) fiberglass, etc. on the outside after sheeting. You might be able to apply it to the inside of the sheeting and let it set up before applying the sheeting, but I haven't tried this. I don't know how well the glass/epoxy (or carbon/epoxy) would bond to the transfer tape. Transfer tape works with either balsa or obechi. However, I believe that it is only suitable for white foam cores. After sheeting the wing you just trim and sand the leading edge of the core/sheeting, and apply your leading edge stock. You can use epoxy or UFO for gluing the leading edge on. The tape will last for years without delaminating.

You can order transfer tape from Dodgson Designs in Bothell, Washington, near Seattle. Email: dodgsonb@eskimo.com.

By the way, I have built quite a few vacuum bagged wings, both wood sheeted, and skinned with fiberglass/epoxy. I like this method of construction, but it is messy and does take more time and equipment/supplies than using transfer tape. You do get a stiffer wing than when using transfer tape, but I doubt that it is much, if any, stronger. Ten thousand Windsongs, Lovesongs, Sabers, Anthems, Camanos, Pixys and Pivots can't be wrong![23]

Transfer tape is the method of wing skin attachment that Bob Dodgson has been using for about 10 years or more. It is 3M product #924 and we use the 3/4" width. You can get it at framing shops, office supplies etc. I wouldn't use anything else after getting used to this stuff. It is a double sided adhesive that has a paper backing on it. You apply it sticky side down and then peel off the paper. The method I use is to put one strip across the LE and TE and peel the paper off. Then starting at the TE apply strips full span not more than an 1/8th of an inch apart work from root to tip and when you approach the LE you will overlap it until the whole panel is done. The while the backing is still on (except for LE and TE) I take a soft cloth and rub the whole thing down and then just peel off all the backing. The trick is to use a dust buster and go over the skin and foam core first to remove dust. You will get a strong bond! Then you just lay your skin on starting at the LE. Have your wing cradle on a flat surface and do the bottom of the wing first. You will be pressing the skin on with the wing in the cradle. When you are pressing the skin on, start from the middle of the wing and press from the center to the tip and then from the center to the root working your way from the LE to the TE. This makes for a strong wing with a uniform amount of adhesive that is still light and no mess. It works great for stabs also! The tape is also available from Dodgson Designs for $6.00 a roll. A 2m plane will take two and larger planes will take three.[24]

Finishing sheeted wings without using plastic heat-shrink coverings can mean savings in cost, weight, and time. One decision is how to color the lower surface of the wing to improve visibility. A method I've used with success is epoxy and colored tissue paper. If you're sheeting wings you most likely already have laminating epoxy and numerous colored tissues are available through artist supply stores and card shops. A dollar goes a long way when it comes to tissue paper.

Cut the colored tissue of choice to the planform you want to cover. Some of the folds and wrinkles can be removed from the tissue paper ahead of time using an iron. Pour out a line of epoxy spanwise onto the surface, then overlay the tissue. Wet out the tissue using an old credit card or a scraper, removing as much of the epoxy as possible. It has been my experience that the tissue is a bit easier to position once there is a little epoxy on it. Make sure that the epoxy has fully penetrated all of the tissue paper and that the paper is flat over the entire surface. Use the scraper to smooth out any wrinkles and move out any air bubbles, especially near the edges of the paper.

Keep in mind that the color of the tissue will darken from the epoxy. Because of the fibrous nature of tissue paper it is translucent such that some of the imperfection in your sheeting may show through. The finished surface is also slightly rough. I'll leave it to the aerodynamics experts to debate whether this is an advantage or a disadvantage. Also, if you used several colors of tissue you may want to make separate pots of epoxy. As you scrape away the excess epoxy some of the fibers are pulled up and will slightly color the residual epoxy.

Let the epoxy fully cure and you will have a durable colored surface that is cheap, easy and fast and to apply, and effective. What else do you want?[19]

7.8 Hinges

You might try arrow shaft hinges. They operate smoothly, are strong, and cause only small disturbances to the air stream. Their disadvantages are they are a little heavy and more difficult to install. I have only used them for flaps but they should work fine for any control surface with up to +/- 90 degrees deflection.

Go to an archery store and buy two aluminum arrow shafts (per hinge). One arrow shaft should fit nicely inside the other with no slop or play. The inner shaft should slide and rotate smoothly. You can probably buy the arrows from the discount bin since you're going to remove any feathers or tips anyway. Cut a small slot every 10 - 15 cm along the outer shaft. The slot should cover an arc of about 100 degrees for a 90 degree hinge. The slots should all cover the same arc (that will make more sense later). The slot should be as wide as the screws used in the next step. Slide the inner shaft into the outer shaft. Carefully drill pilot holes into the inner shaft through the slots in the outer shaft. All the holes should line up with each other. Screw in sheet metal screws into the holes. They should stick out about 6-8mm. At this point the hinge action should be obvious. Cut the control surface away from the wing so that the wing is slightly thicker at the cut than the outer shaft. Dig out a little foam so the hinge is almost totally contained inside the wing. Bore small holes in the control surface foam to accommodate the screws sticking out of the hinge. Roughen the outer shaft opposite the side with the screws sticking out. Put a little Vasoline in the hinge slots, then epoxy the screws into the control surface. Be careful not to get epoxy on the arrow shaft! After the epoxy cures, mix up more epoxy and glue the outer shaft to the wing. Be sure to align the hinge so you get the proper motion.[1]

I know there are as many opinions about control surface hinges as there are people reading this e-mail.

I have searched high and low for a good hinge tape that works on all of my planes. While the stuff sold by Airtronics and Charlie Richardson is great, I have a problem paying $1 to $2 a foot for this stuff.

The best tape I've found is 3M 845 Book Tape (3M P/N 3M845-15). This stuff is a 1.5" wide, mylar based tape that will stick forever. What's even better is it cost about $.09 a foot. I use one strip on the top of the wing only and have never had a problem with it pealing or cracking.[25]

7.9 Spars

As Don Edberg already pointed out, carbon fiber is NOT bad in compression. Its actually very good in both compression and tension. The problem with carbon fiber is in the way it is used. Because it is so strong, you can conceivably use very little carbon fiber to have seemingly adequate compression or tension strength in a structure. But, because you have so little material, the structure will suffer from buckling in compression due to the slenderness of the carbon fiber member (usually a layer). So you have to use a lot more of the expensive carbon fiber layers to get adequate resistance to buckling in compression. You might as well use fiberglass on the compression face of the member since you have to have a thicker layer. Another way around this carbon buckling problem is to adhere the carbon to another thicker member like wood sheeting or spars or even more fiberglass. The problem you then need to watch out for is strain incompatibility in the composite structure. You generally don't need to worry about the thin carbon fiber layers used on the bottom face of wings unless you expect to pull a lot of negative G's (like on an aerobatic model). :-)

Ron B Cheroske is getting nearest to the point. The problem is that you are looking at it from the material strength rather than the structural viewpoint. The fact that carbon is strongest under tension is of itself irrelevant, its the application that determines the usage.

The top spar is always under compression and the lower one is under tension. Be careful here because the term top only has meaning for a given loading direction. The shear web is there to prevent the top spar buckling, some form of shear web for at least some part of the span is necessary. Now materials under compression usually perform worse than those under tension, so much so that you can use 33% or 25% of the top spar material for the bottom spar. For heavy winch towing where the zoom launch puts a substantial negative load on the wing I always use about 50% for the bottom spar.

Carbon actually has poorer compressive strength than glass so glass could be used instead. The penalty however may be extra weight, although this is likely to be minor in a model. The other problem is that it is better to use materials that are compatible with each other with temperature change, so carbon top and bottom is probably the best idea. The shear web can be eliminated if the carbon spar cap is wide, an inch or so, and you are out beyond 50% of the half span, the load has dropped off to about a third or less of the root load.

I have heard of people suggesting that the wing can be strengthened by beefing up the bottom surface, it ain't so, wings usually fail at the end of the joiner or somewhere towards the wing root due to stress risers and top spar failure. Strengthening the bottom surface may actually make the situation worse and is heavier than reinforcing the top surface

Have a chat to a stress engineer, (o.k. most of us married one) and ask about cantilever beams. The field is well understood and easy to understand, there really should not be any myths or misinformation about this area. Alternatively, blow your mind and read Ferdi Gales structures book, B2 Streamlines carry it.[9]

Forget the COM, Moment of Inertia, and all them great formulae... Let's think conceptually here. The compressive force in the top spar must equal the tension force in the bottom spar. Either that, or the wing will fly off of the fuselage, or crush the fuselage. For all of you nitpickers out there, this assumes that the spar carries all bending loads... I add material to the bottom spar, and I've reduced the stress on the bottom spar for a given bending moment, but did not change the stress on the top spar (the force on the top spar is unchanged with the same bending moment and spar depth). Of course, what I did do, is increase the stiffness of the spar. If the failure is a compressive failure (almost all model wing failures are...) the wing will fail at a smaller flex due to the increased stiffness (use COM and Moment of Inertia here...). If I increase the spar depth, the forces decrease for a given wing bending moment. Of course, the converse is true, which is why skinny wings have big spar caps.

Hidden in the above is a hint, which I will now spell out clearly. For a plane that sees mostly positive g's, use more material on the top spar cap than the bottom. You will be happy that you did.[37]

Joe Wurts is correct about the effects of changing only one spar cap not changing the stress in the other. Here is why.


: --> Fs |


: |

: h1 |

: |

----+--- Neutral Axis |

: |

h2 : |


Fs <-- : |


: ^

: L | Fv

This is a simple case to illustrate the principles involved. A vertical force, Fv, is applied at distance L from the plane at which we want to calculate the loads in the spar caps. The tension and compression LOADS (not STRESSES) must be equal because there is no spanwise load applied and forces must balance in the spanwise direction. There will be vertical shear forces in the spar caps to resist Fv, but we will not worry about them now.

Assume no thickness for the spar caps so that

h1 + h2 = t = thickness of the wing

The moment balance equation becomes

M = L * Fv = h1 * Fs + h2 * fs = Fs (h1 + h2) = Fs * t

Thus, the loads in the spar caps are totally independent of the location of the neutral axis. If you increase the cross sectional area of one of the spar caps, the neutral axis will move closer to it, but the load will stay the same. The STRESS in the unchanged cap will remain constant, while the stress in the thicker cap will decrease. Increasing the overall thickness of the wing will reduce the loads in both spar caps, but changing one of the spar caps will not affect the load in the other. This analysis is valid for situations where the thickness of the spar caps is small compared to the overall thickness of the wing.

For homogeneous materials (i.e. solid spruce spars like are used on a lot of homebuilt aircraft), the failure mode will usually be a tension failure on whichever surface is in tension. For structures with long skinny spars, you generally see a buckling failure in the spar loaded in compression. The function of shear webs is to prevent the buckling. Making the spar that will be loaded in compression thicker increases its moment of inertia and makes it more resistant to buckling.

Regarding Joe's comment about the stiffness of the wing, if you recognize that the elongation of the unmodified spar cap will be the same, the greater distance the neutral axis means that you will get a larger radius of curvature and the tip will deflect less. Isn't it great when you can actually find a set of equations the describe what you KNOW has to happen?[28]

I think that I've opened a can of worms on the spar cap issue, that has evolved to bagged wing stuff. i.e., what is the best lay-up on a bagged wing?

For simplicity, I'll not mix different stiffness materials. That is, no partial glass/carbon lay-ups. From numbers and experiment, the best lay-up on a strength/weight standpoint is with the upper surface being 2-2.5 times thicker than the lower surface. This is highly dependent on the camber and thickness used. The sample for the above is with an Eppler 374 airfoil. This is not the best stiffness/weight, but the best from a most bending moment in the positive g situation. A further caveat is that the foam used is useful from a buckling stiffness perspective, in other words, no white foam. My very first vacuum bagged wing had white foam and folded on about its fourth launch. One wing folded over the other, and it fluttered to the ground. When I got to it and picked it up, it looked entirely undamaged, as the wing flopped back into place and the skin was unbroken![37]

It's interesting that the original opening of this thread had to do with the reinforcement of spruce spars with carbon fiber on the bottom surface. I guess there aren't many sailplane folks in California who remember that there are still people who use spruce spars in built up wings - to which my tests are indeed directly applicable.

Since my original tests (run some years ago) had to do with strengthening of spruce spars, I knew that a thin layer of carbon tow on the bottom of the spar increased its breaking strength by about 30% (in the tests I ran). I even know why and how it strengthens it. I was surprised when knowledgeable people quickly resoponded to the original post - saying that the Cf didn't strengthen the spruce spar.

In my do-it-yourself test, the foam only takes the place of the spruce of the original post. The net effect of reinforcing a more flexible material (foam or wood) with a stiff material (CF or strapping tape) on the tension side, is certainly relevant to wings where wood spars carry most of the loads - whether they have foam cores or not. Since people in areas other than California do use spruce spars, and even fly sometimes even with built-up wings, I thought the information might be valuable to them - particularly since some others had told them otherwise. [38]

Herk Stokely is indeed correct that reinforcement of the lower spar cap of a built up wooden spar will increase the strength of the spar system. It does this by lowering the maximum stress in both the upper and lower caps, for a given bending moment.

When the spar caps (or skin) is very thin compared to the depth of the spar (as in composite skinned foam wings) the loads in the upper and lower caps must be the same in magnitude. The caps function basically in pure tension or compression. When the spar caps are properly sized they both operate at the same fraction of their failure stress - that is, they fail at the same time. When one spar cap is strengthened without significant thickening the load on the other cap is unchanged and the failure load is unimproved. However, when the caps are thick compared to the overall depth of the spar (as in a built-up spruce spar) the story is different. In this case the spar caps are operating both in tension and compression as well as in bending. By reinforcing one cap, its independent bending stiffness is increased and this slightly unloads the other cap at a given bending moment.

I have run some sample cases. Assume that the overall depth of the spar is 1.0 inch; that the bending moment applied is 200 in-lb; and that carbon fiber is 10 times as stiff as spruce:

1. Spruce spar caps 1/4 inch square top and bottom. This symmetrical arrangement has a maximum compression stress in the outermost upper fiber of the upper cap of 5486 PSI, and a maximum tension stress in the outermost lower fiber also of 5486 PSI.

2. Upper cap of 1/4 inch square spruce. Lower cap of 1/2 inch wide by 1/4 inch deep spruce. The neutral axis is 1/3 inch up from the bottom. The maximum compression stress is reduced to 5389 PSI, a 1.8% reduction compared to case 1 above. The maximum tension stress is reduced to 2695 PSI, a 51% reduction.

3. Upper and lower caps of 1/4 square spruce, but the lower cap is reinforced on the lower side with 0.060 inch of carbon fiber, 1/4 inch wide. The neutral axis is only 0.257 inches up from the bottom. This results in a maximum compression stress in the upper cap of 4543 PSI, a 17% reduction compared to case 1. The maximum stress in the lower wood cap is 1207 PSI, a 78% reduction. The maximum stress in the carbon cap is 15,740 PSI.

From these examples it is clear that reinforcing one spar cap will reduce the stress in both caps, but the biggest effect by far is on the cap which is reinforced. Effects on the other cap are modest. [22]

7.10 Pivots, bell cranks, and control horns

[Installing a pivot] The problem definitely lies in the "pivot-support structure". If properly done, you should have very little, if any slop. Without going into the why's of the slop in your pivot-support structure, let me tell you how I resolved the problem.

First you should understand that I have invented very few things in my life and the few things I did invent I later found out someone had the audacity to improve on my invention prior to my inventing it. What I am about to share with you is something I learned from one of the sages in our club. Instead of shaving the brass pivot rod tube flush with the vertical stab, allow about a 1/16" to extend on either side of the stab. Once you have the horizontal stab positioned correctly, tack the pivot tube with CA (be sure to rough up, with sandpaper, only that section of the pivot tube that will be glued - the exterior 1/8" of both ends). Be careful not to have the CA run down the tube particularly on the outside as it will freeze the bell crank to the pivot tube. If some CA gets on the inside you can always clear it with the proper sized drill bit. Now that you have the pivot tube tacked, simply use some 5-minute epoxy to form a fillet around the pivot tube one side at a time. Make certain that the vertical stab area around the pivot tube is roughened with sandpaper and cleaned before applying the epoxy.

Since I began using this technique, I have not had a single problem with a "floating" stabulator (God forbid I should say "flying stab"). BTW, it will be necessary for you to bevel the area around the pivot rod tube of each stab in order to get a nice clean fit between the stabulator and the vertical stab. If the brass pivot rod tube is already installed in the stabulator, simply glue a 1/16" or thicker, if required, balsa shim onto the root rib and sand flush with the airfoil. Locate and drill the holes for the pivot rod and the locator pin and then bevel the area around the pivot rod tube -- I use a counter-sink bit and rotate it by hand.[6]

7.11 Labels

Sweet and simple...I created what I wanted to have on the decal in my favorite word processor (MS word) with whatever style print appealed to me, and printed it out on the laser printer. I then took standard clear plastic package tape (like they use for UPS packages, etc. This brand name happens to be 3M Highland 3710 tape) and laid down a strip over the printing. Rub it on nice and solid, then cut out what you want to use. Soak it in water (articles recommend no more than 3 minutes...I found it didn't make much difference if you went longer. Let one soak for 30 minutes w/out difficulty), then just 'rub' the paper backing with your finger until all the paper rubs off. The actual print will be embossed in the tape. Once the tape dries, the adhesion quality returns, and you can simply tape it on your plane/radio/whatever-where ever you want. Works pretty slick, and is low-cost.[26]

7.12 Mixers

From: Vince Mitchell

Is there a way to mechanically mix a v-tail for a skeeter without compromising too much weight, or $?


There sure is. I have used a simple sliding tray for years and have never had a problem. The gist of it goes like this.

Servo #1 is hard mounted in fuse. A second servo is mounted such that the fixed servo #1 can slide it back and forth in the fuse. A pushrod runs from each side of the sliding servo to the tail surfaces. Thus when you ask for elevator, #1 slides #2 back and forth, moving the tail surfaces in unison. When you ask for rudder, #2 rotates, pushing one pushrod and pulling the second. The tail surfaces now operate opposite each other affecting rudder control.

As for the mounting of the sliding servo, I have always used small scraps of servo rails glued to short sections of roughed up outer pushrod sleeves. These slide on sections of inner rod, mounted to the fuse via light balsa bulkheads, usually half height or less. Remember that in a hard landing the shock of servo #2 is taken by the mounting and gear train of servo #1. Thus the mounting of #2 does not need to be bomb proof. To save some complexity and weight, trim the mounting tabs from a mini servo and superglue the two scraps of outer nyrod right to the case.[17]

This does work fine, there are only 2 problems. 1 mechanical slop in the linkages and tray (chopper ball links should stop this). Secondly if (when) you crunch it the elevator servo has to try and stop the mass of the rudder servo, a guaranteed recipe for stripped gears.

Dubro make a servo top rocking mixer (for choppers?) that gets round this, however there is some interaction of channels at full throw, it's not too bad though.[27]

Bill Kournikakis had a question about inexpensive electronic mixers, so I thought it appropriate to attach below my description of one, which I have used successfully in two applications and think well worth describing here.

There is a clever little device that I recently bought, which can perform a variety of interesting electronic functions of use in inexpensive RC sailplanes.

The device is called a "Digital Aircraft Doohickey", or D.A.D., and was reviewed in the 11/93 Model Airplane News. It sells for $40 from Hobby Supply South, 5060 Glade Road, Acworth, GA 30101, (404) 974-0843.

The D.A.D has four modes of operation, set by toggling a pair of small DIP switches on one end of the device. Note that these four modes are all mutually exclusive, i.e., only one can be selected at a time.

- master/slave mixing of two channels

- elevon, V-tail, flapperon mixing

- ATV and/or exponential servo response

- servo pacing (movement slowdown)

The amount of mixing, etc. is further defined by toggling one or more of six remaining DIP switches on the device, making it a very flexible unit indeed. It measures 1.7" x 1.1" x .7", and weighs all of .6 ounces. The current draw is not specified, but it claims to be "low power". There is no obvious high current component visible on the device (LED's, etc.), and my guess is that it draws only a few mA. It is accompanied by a 10-page user's manual, which clearly describes how the device is employed in all of its modes.

I have used the device to mix in down elevator with flap deployment on a 2M floater, and have also used it to perform V-tail mixing in an HLG. It seems to work well, and I wouldn't hesitate to recommend it.[49]

If you want to use a mixer for 2 channels only and don't want to spend the $ for a new radio. Try either a Christy (sp?) mixer from ACE at your local hobby shop or the Quillen mixer from

Quillen Engineering

561 North, 750 West

Hobart Indiana 46342-9438

The Quillen mixer was a construction article in the Dec '94 & Jan '95 RCM's and it allows for old (upgraded RF) radios, new radios, and mixing for 25% flaps, 50% flaps, 50% mixer and 100% mixer using a microcontroller to do the mixing. Art Quillen sells these in various forms of completion anywhere from just the controller program on disk for $5 all the way to a complete assembled unit (less connectors) for $29 ('95 prices). I built my first one from an unassembled kit and loved it. I have also built several more from scratch and they work out great.

This may help if you are limited in budget and do not need extravagant computerized functions. It will definitely not help if you have some money burning a hole in your pocket or have already had your heart set on taking the plunge.[50]

8.0 Contests

8.1 Introduction

8.2 Contest directors (CDs)

8.3 Thermal Duration

8.3.1 Frequency control

8.3.2 Launch order/windows

8.3.3 Pop-offs

8.3.4 Landing circles

8.3.5 Timers

In most contests you try to fly for some period of time. Your timers job is to keep track of when your flight officially starts, ends, and let you know how much time you have left. Your time officially starts when the winch or hi-start line drops off your plane. Your time ends when you touch anything that is in contact with the ground. Note that this makes it possible to stop your time without landing. I know one pilot who was late coming down from a thermal. He flew his plane through some tall grass several hundred feet from the landing circle (stopping the clock), then rose out of the grass and flew his plane toward the landing circle. He had a lousy landing score, but his time was within one second. Your timer will also usually watch for indicators of lift (planes, birds, bugs, etc.), threats to your safety (full size aircraft, low landing approaches by others...) and so on.

8.4 Slope

8.4.1 Speed

8.5 Scoring

9.0 Glossary

All definitions by [1] unless noted otherwise.


Almost Ready to Fly - A kit that requires very little assembly. ARFs are generally considered poor flyers.


A chemical which causes CA glues to cure almost instantly. Note that accelerator (a.k.a. kicker) often causes the CA to boil resulting in a weaker bond. The combination of thin CA and accelerator gets very hot very quickly. It can smoke, scorch balsa, and cause second degree burns. See section 7.1.2


Bill Swingle asked about rules of thumb regarding aileron size/deflection. The following information is from AEROSPACE VEHICLE DESIGN by K. D. Wood and THEORY OF WING SECTIONS by Abbot & Von Doenhoff. These are college texts I used back in the 60's & 70's. The K. D. Wood book in particular is just full of charts and rules of thumb and is not terribly technical, so it might be of interest to modelers. Unfortunately, it doesn't have airfoil data for any of the modern sections.

Abbot & Von Doenhoff present data for flapped airfoils (you can consider ailerons to be flaps that move in opposite directions) that shows the section lift increasing even up to 70 degrees deflections. However, drag starts rising significantly beyond about 30 degrees. For ailerons, the drag is probably a killer. 30 degrees is probably reasonable, but I seem to remember that the Cessna 150 had 45 degrees up and 30 degrees down, so if you use aileron differential, the up aileron could easily go beyond 30.

K. D. Wood's book give some general ranges of the control surface sizes and deflections for full scale aircraft.

Control surface sizes and deflection




Fraction of wing area

0.09 - 0.10

0.075 - 0.085

0.16 - 0.20

Fraction of local chord

0.18 - 0.29

0.50 - 0.60

0.50 - 0.55*

Deflection (degrees)

15 - 25

15 - 30

10 - 30

* He also notes that elevators as small as .25 chord can be sufficient for "high speed designs"

A word of caution: this is what works for full scale aircraft. Low speed designs tend toward larger control surfaces and our application is definitely low speed. Also, the Reynolds number effect is going to get us. My advice is to look at models that fly well and copy them. That's what the big guys do. The Cessna 170 was a scaled up 140. The 180 was a 170 with a bigger engine and a bit more cabin room. The 172 and 182 were the 170 and 180 with a nose wheel. The 150 was a 2/3 size 172....etc., etc. The Cardinal was the first significant departure from this family tree in ages.[28]


There are hundreds of different documented airfoils. In addition, there are thousands of minor tweaks people make to the documented airfoils which can radically change their flight characteristics. Each airfoil flies differently. Most are named after their inventor. Some of the more popular airfoils are:

Clark-Y: flat bottomed, flies ok, old design, easy to build.

RG-15: flies fast, Medium age design

SD7037: Flies medium fast - wide speed range, new design.

E3021: Medium age design, a tad slow but good all around.

Each design has advantages and disadvantages. If you want an in depth answer, get SoarTech #8 (someone on this exchange sells it). Until you start designing or modifying others designs none of this matters. Simply ask for a good plane.

Alphabet soup

F3B, F3J, etc.


See aspect ratio.

aspect ratio

A few days ago I sent out a critical reply to a discussion on aspect ratios. I did not however provide any insight or answers. I apologize and will make amends now. Many people have asked for value of the best AR, instead of technical jargon. So I wrote a program that looks at all of the drag components and optimizes AR for a Maximum L/D condition. NOTE: The optimum AR depends highly on flight condition (High lift, low lift etc.), so I picked max L/D as a good overall optimization point. First a quick discussion on the optimization process, (without long equations) Cd=Cdp+Cd(vortex)+Cd(lift dependent viscous), Where Cdp is the parasite drag and is a function of (Re#, wing thickness, and skin friction coefficient). Cd (vortex) is the inviscid vortex drag and is a function of (lift coefficient, Aspect Ratio and inviscid wing efficiency (e inv)). The Last term is the lift dependent drag coefficient and is a function of (Cdp and lift coefficient) For best L/D Cdp=Cd(vortex)+Cd(lift dependent) (a fact, trust me). Combining these equations and balancing RE# effects with AR effects, an optimum AR can be determined.

Here are some results.

Starting assumptions: Velocity=35ft/s, Average chord =8", e inv = 0.98,

Weight =6 lbs.

Results: OPTIMUM AR =12.5, corresponds to 100" span

NOTE: overall wing efficiency at this condition (e = Oswalds efficiency factor) is 0.8

Using the same method and calculating optimum AR for a full-size glider Starting assumptions: Velocity = 90ft/s, Average Chord =4 ft., weight =1000# (I made these numbers up, I don't know how accurate they are) Results: Optimum AR = 25, wing efficiency =0.74

These results clearly indicate that as RE# decreases, optimum AR also decreases, which is why Full-size AR are not efficient at model RE#'s. Also wing efficiency decreases as AR increases, due to viscous effects. These last two facts are what I previously posted without the explanation. NOTE: These are approximate values, I used numerical CD methods to approximate the drag components. Accuracy could be improved by using wind tunnel drag data for your specific airfoil. (If you have the data available at your desired RE#) Well I hope this helps. If anyone would like a better explanation and the governing and optimizing equations, then e-mail me your mailing address, and I will be glad to send it to you. So why believe me? I am an Aerospace Engineer for NASA Ames Research Center, where I am a Test Manager at the National Full-Scale Aerodynamics Complex. I am also completing a masters degree this march, specializing in applied aerodynamics. (Final exams are coming soon so all of these equations are fresh in my mind)[29]


On breezy days the air you are flying in is turbulent. From an engineering perspective, this turbulence can be described as base wind speed with a rotating vector added. For example, if your base wind speed is 10 KPH, with a 4KPH rotating vector, the rotating vector will sometimes add to the wind speed, and sometimes oppose it. The windspeed will rotate through 14KPH (10 + 4), 10KPH (Rotating vector pointing down - sink), 6KPH (10 - 4), 10KPH (Rotating vector pointing up - lift), 14KPH... Of course, this is a gross simplification of reality, but it works for our purposes.

If you are flying through this breeze at 2KPH above your stall speed you will spend around a third of your time in a stall. The plane will not fall out of the sky because the inertia of the plane will carry it through the momentary stalls. However, these momentary stalls will ruin the way your plane flies. It will feel mushy and sink faster than expected. If you were to dial in a few clicks of down trim, enough to increase your airspeed by at least 2KPH, your plane would cease the momentary stalls and fly much better.

Adding ballast forces your plane to fly faster, taking you out of the momentary stall region. It also increases your inertia so the rotating vector has less of an impact on your plane. Unfortunately, it also forces you to use more of your energy budget (potential + kinetic) to hold up a chunk of lead. On turbulent days this is a good trade off.

Frank Deis (1974 NATS winner) is writing an excellent book that covers this and many other RC soaring topics. When it is published, I'll let you know.

Paraphrased - What are good ways to put ballast in a plane?

The best way (IMHO) is 1/2" brass tubes at the CG in the wings. You pour lead plugs slightly smaller than the tube. When you need ballast, you slide it into the wing. Add balsa sticks to fill any extra space in the tube.

Another way is to glue a piece of hook velcro inside the fuse (at the CG). Glue the loop velcro to the lead. Simply press the lead into the plane and your ready to go. It\Qs quick and works well. The velcro takes shear forces very well, even a severe crash will not cause the lead to break loose.

For 2-meter and larger planes, don\Qt bother with less than eight ounces of lead. If you think you need less than that, you don't need any at all.[1]

Safety issues which need to be addressed when considering melting and casting lead:

1) The melting of lead should always be done outdoors, as outdoors is the only place considered to be a well ventilated area. Indoors, even with an exhaust fan, is _not_ a well ventilated area.

2) Be careful when it comes to choosing materials for the making of a mould or form. Dry wood is OK, but as mentioned in a previous post, it needs to be lined. Also, forms usually cannot be glued together, as the heat from the molten lead rapidly deteriorates the glue bond. Nails or screws need to be used.

3) As an additional note, there are some who use "plaster of Paris" as a mould. This is a rather handy material, as you can press the nose of your favorite model into a container of plaster and have a fairly accurate mould for casting a lead slug which can then be inserted neatly into the front end of your plane. However, several fellow modelers have had negative experiences using this technique. The complaint is that it seems the plaster never dries out, even after a couple of weeks in a dry environment, and steam is released when lead is poured into the mould. After being presented with this scenario by Bruce Abell (Australia) we came up with the following explanation: The plaster is dry; that is, it is not damp. But there is water being held in a chemical bond with the plaster. In fact, it's that chemical bond between the plaster and water (hydration) which makes the plaster harden. As with other chemical reactions, this reaction can be reversed with sufficient heat. Thus hardened plaster can be broken down into its original components, plaster and water, by heating. Pouring molten lead into a plaster mould breaks the chemical bond at the surface of the mould, releasing water in the form of steam. This can be quite dangerous, as the molten lead can be forcefully expelled from the mould by the pressure of the released water vapor.

Everything we do is dangerous to some extent. Being forewarned allows us to take precautions which will reduce to a minimum the risks involved. Always melt lead outdoors; be careful when choosing materials for moulds and forms; be aware of the dangers inherent in using plaster moulds.[49]

Watch the fumes from [lead]. This stuff is BAD! I worked as a cable splicer for the telephone company and we got a lot of lectures on health problems related to inhaling fumes from the solder pot (lead). I personally use bird shot from the local gun shop. Find one that caters to the "re-load" customers- look in the phone book. Get the smallest bird shot for reloads of shotgun shells. For flat lead pieces go to the local tire shop and ask for the discarded balance weights. Hammer these flat to whatever thickness you require. Also the tire shops have flat weights for use on mag/alum wheels. The way I balance my gliders is:

1. Assemble the whole thing.

2. Mark the design balance points on the bottom of the wing.

3. Tape a paper cup at the nose of the glider.

4. Put the glider on the balance stand -a piece of wood with two vertical dowels-

5. Align the balance stand with the balance marks on the wing.

6. Cut up about 1 oz. of the flat lead and drop it (them) into the paper cup.

7. Dump enough bird shot into the cup to bring the glider into balance.

8. Take out the flat lead.

9. Disassemble the glider and hang the fuselage nose down.

10. Mix up some thin epoxy or white glue and paint a bit on the inside of the nose. The glider not yours.

11. Start pouring in the bird shot; watch to see if the adhesive flows through the shot; if not add a bit more glue.

12. Keep this up until all the bird shot is in the glider and top off with another bit of glue to cover the surface of the shot.

13. After everything is dry put back in your flat lead and every thing should be in balance.

14. I cut or add pieces to the flat lead for final trim.

The bird shot cost me $2.00 per pound and sometimes I can get used shot for less. The flat lead was free.[31]

Gary S. Baldwin wrote:

> I use bird shot (as small as I can get) mixed with epoxy to balance my

> planes too, but I pour the birdshot and epoxy mix into a plastic sandwich

> baggie. This way the lead can be removed if needed. It works for me!

I have a favorite trick using bird shot. I mix it with modeling clay, and pack it into the nose for ballast. Real simple to change; takes up a little bit more space than melted lead, probably close to the epoxy trick; and I can take it out, but I don't need anything to secure it.

It sure beats spreading lead all around after one of the (locally) famous Kirchsteinifications (read crash). <G>[32]


Electro-chemical cells used to produce electricity. Usually NiCads. See section 2.5.4


Some fuselages are built using a method called "pod and boom". The pod is basically a bubble that extends from the trailing edge of the wing forward and contains the electronics of the plane. The boom is a pipe extending back from the pod to the vertical and horizontal stabilizers.

boundary layer

The thin layer of air next to a surface, usually the wing. This layer is a small fraction of an inch thick and is usually "attached" to the wing.


See crow


Cyano-Acrylate. Super glue. See section 7.1.2


See carbon fiber.


See center of gravity.


See CA.


A slight "hollowing" of the underside of the wing between the spar and the trailing edge of the wing. This is often built into the wing, but is most obvious when flaps are lowered (variable camber). The primary effect is to increase lift and drag. Also see reflex.

carbon fiber

Incredibly strong fibers made from nearly pure carbon. See section 7.3

center of gravity

The static (nose to tail) balance point of the plane. This is usually around 35% of the mean root chord length back from the leading edge of the wing.

computer radio

A transmitter which allows the pilot to set up various modes (i.e. launch, landing, etc.) and mix the various inputs (i.e. aileron to rudder) to make controlling the plane easier. These transmitters cost significantly more than "normal" radios. They give advanced pilots a small advantage by reducing their work load so they can concentrate on finding thermals or nailing their landing.

control horn

The lever arm attached to a control surface, usually near the hinge. It is connected to the servo, usually with a push-pull cable. The equivalent structures at the servo end are called servo arms.



Material used to cover the wings and fuselage of the plane. Usually a plastic heat shrink material such as Monokote or Coverite. See section 7.4


On a six-servo ship with a computer radio both flaps can be lowered and both ailerons raised. This configuration provides tremendous drag to slow the plane down and is known as crow or butterfly.


The relative angle of the wing and the horizontal stabilizer. On "normal" planes these two surfaces are not parallel. The stab has around -3 degrees of incidence relative to the wing. This contributes to stable flight throughout the speed envelope.


The upward bend of the wings at the fuselage. This makes the plane easier to fly.


The 180 degree arc through which your plane must fight the wind in order to get back to you. A region beginners and those with slow, draggy planes should attempt to stay out of.


The force that resists your planes forward motion. This comes from two primary sources: 1) Induced drag is an unavoidable by-product of the creation of lift by your wings. 2) Drag related to pushing the air molecules out of the way. This is related to how streamlined your plane is and its wetted area, which is a fancy way of talking about the frontal area.

dual rates

A feature on many radios that reduces the sensitivity of the control sticks. This is valuable when you are in a thermal and you want all control changes to be small and efficient. If you have the feature available you should fly with dual rates enabled all the time except launch and landing.


The control surface which controls the planes motion about the pitch axis. Many beginners think of this as an altitude control. That is wrong. It is a speed control.


A strong, durable adhesive created by mixing a resin and hardener. See section 7.1.3


Expanded Scale Voltmeter. Any voltmeter which gives you a resolution of 10mV or better over the range of interest. Most analog voltmeters do not give enough resolution to allow you to estimate how much charge is left in your battery pack (because the NiCad discharge curve is so flat). An ESV does. Note that most digital voltmeters give enough resolution. The little meter on your transmitter is an ESV.



Filler material placed in the corner of a joint to reduce stress at the joint. Balsa is usually used as the filler material, but baking soda and thin CA is frequently used too.


Use of flaps in concert with ailerons to reduce drag and improve roll rate. This requires the use of a computer radio.


Control surfaces (almost always on the trailing edge of the wing) which can change the camber of the wing. By dropping down up to 25 degrees they increase camber which increases angle of attack and lift. By dropping over 50 degrees they dramatically increase drag, slowing the plane down. By raising them up to five degrees they decrease camber and reduce angle of attack, causing the plane to speed up.


Any of a variety of lightweight plastic/air formulations. Styrofoam, gray, blue, and Spyder are some varieties. They are used to make the `cores` of composite wings. They are cut using an electrically heated wire following a template at either end of the foam core. For large wings a spar is built and glued into the foam. Smaller wings do not need spars. The foam cores are then covered with a skin of fiberglass, obechi, or balsa. Most of the strength of the wing comes from this covering.


A small slope soaring ship made largely of foam and difficult to damage. They are used primarily in slope combat. The objective of this pastime is ram other planes with your plane as often as possible to knock your opponent out of the air. Note that playing combat with unsuspecting novices will likely result in the destruction of your plane, transmitter, and you. In addition, your name will be reviled throughout the Internet through all eternity (i.e. Sergio).


Short for Fuselage. Pronounced like the body of the plane, not an electrical device for stopping current flow.


The body of a plane that holds the wings and stabilizers together. Note that flying wings have none.


Abbreviation for Gentle Lady. This plane, kitted by Carl Goldberg Models, is known throughout the hobby. It is a good two meter plane for beginning and experienced pilots. Often used as the definition for the word `floater'. Does not penetrate well.


See fiberglass.

glass slipper

An aerodynamically SLIPPERy plane with a fiberGLASS fuselage.

ground loop

A loop terminating just below the air/ground interface. See re-kitting.

ground speed

The speed of the plane referenced to the ground. Note that this has little to do with the planes airspeed which is far more important.


A launch system consisting of a large elastic substance with a length of string tied to one end. The elastic is usually surgical tubing, either 1/4" or 3/16" outside diameter. Sometimes bungee cord material is used for the elastic. The string is typically four times as long as the elastic.

The free end of the elastic is nailed to the ground. A parachute with a steel ring is attached to the free end of the string and this ring is placed over the towhook on the bottom of the plane. The elastic is stretched downwind (about three times its relaxed length for surgical tubing). The plane is then thrown horizontally in the direction the hi-start is pulling (into the wind). This causes the plane to climb about as high as the string is long (depending on wind). At the top of the launch the ring will automatically slip off the towhook and the parachute will return the hi-start to the ground.

hi-tech ship

An aerodynamic ship with lots of servos. Almost always an open class plane.


joiner box

In a plane with a two (or more) piece wing a rod (often steel) is used to join the wing segments. The rod slips into a tube in each wing segment. The construction around this tube is called the joiner box. The box is usually part of the spar. For a two piece open class wing the strain in the vicinity of the joiner box can be calculated at thousands of pounds per square inch during a hard winch launch or crash.

laminar air flow

leading edge

The front of the wing - The part that splits the air into a pair of streams going over and under the wing.


Anything which pushes your plane up without reducing its airspeed. Usually refers to thermals and slope lift.


See mean aerodynamic chord.

mean aerodynamic chord

The average width of your planes wing after considering that your wing is probably not rectangular.


Incredibly light powder that is mixed into epoxy to reduce its weight without significantly reducing the strength of the bond. This stuff is sold by volume, not weight. If it was sold by weight the numbers would be negative! It is used in places where you want to fill large voids without adding weight.


Parties that soaring types go to. Also, electronic or mechanical devices which mix two or more input signals and send them to one control surface. The mixing is often non-linear. For example, it is fairly common to mix the aileron and rudder signals and send that to the rudder. This allows automatic turn coordination on planes with both rudder and ailerons. See section 7.12


A brand name covering material. It is a heat shrinkable plastic with a heat activated glue on one side. It comes in a variety of colors. Other brands are Coverite, Ultracote, Solarfilm, and Black baron.


New In Box. Often the way planes are sold after the owner realizes he purchased the kit ten years ago and still hasn't found time to assemble it.


A tropical wood often used in the furniture industry as a final finish layer. In modeling we use it to sheet foam core wings. Obechi is a dense, cream colored, fine grained wood. It is commonly available in sheets up to 4'x1'x1/48". Before attaching to the wing it splits very easily. After attaching it is very durable.


Refers to a planes ability to increase air speed without losing all it's energy to drag losses. In general a plane that looks sleek and aerodynamic will penetrate well. A light boxy plane probably won't.


Rotation about the wing axis.



Polyhedral refers to the additional upward bend in the wing about two-thirds of the way out on a wing. Note that flat wing planes have no polyhedral (that's sorta the definition). Polyhedral wings are more stable than flat wings. It's the polyhedral that makes your plane turn. The rudder causes the plane to yaw which causes one polyhedral surface to produce more lift than the other, causing your plane to roll. Without the poly, no roll, only yaw. In addition, the poly makes your plane more stable (easier to fly) since it counteracts non-yaw-induced-roll.


The communications link between the pilot and the plane. Could refer to any component of the system, but usually refers to the transmitter.


The gizmo in the plane that converts the radio signal into signals the servos understand.


Returning your plane to the condition you received it in - lotsa little pieces. Often the result of a ground loop.


Raising the flaps about three degrees is called reflex. This decreases the wings angle of attack and causes the plane to speed up.


Any of various devices used to bring the end of the winch line back to the winch in preparation for the next launch. This includes medium sized golden dogs and children on dirt bikes. It usually refers to a mini-winch which is also attached to the winch line near the parachute. During launch fishing line is pulled off the retriever by the winch. After the plane leaves the winch line, the retriever is engaged and pulls the end of the winch line back to the retriever. Typical cycle times for a winch without a retriever = 15 minutes. Typical cycle times with a retriever = 1 minute.


In built up construction, the structural elements which define the shape of the airfoil.

ridge lift

Same as slope lift, see section 4.2


Rotation about the fuselage axis.


The end of the wing that makes contact with the fuselage.


A mass of air rotating about a horizontal axis. Think of a horizontal tornado. Rotors usually form on the lee (downwind) side of hills, dams, and other obstructions. Often these obstructions make good slope soaring sites. Rotors have this nasty habit of grabbing your plane and slamming it into the ground. If you are slope soaring, stay away from the downwind side of the hill (unless you're really good like Joe Wurts, then you can take advantage of the rotor).


The control surface used to induce yaw. Also see polyhedral.


Electro-mechanical devices used to position the control surfaces.


See wind shear.

shear web

The middle part of a spar. When a spar is under a lifting load (bending upward) the top of the spar tries to bend down toward the bottom of the spar. The shear web is glued between the top and bottom of the spar to prevent that from happening.


A "tooth" or series of teeth under the nose of the plane. They dig into the earth and stop the plane quicker. This can be a real advantage when landing during a contest. Some people do not like them for philosophical or safety reasons.

slope lift

Same as ridge lift. See section 4.2


A structure (usually balsa and spruce) which bears all the load in a built-up wing and some of the load in composite construction. Note that small composite wings do not normally use a spar. See section 7.9


A control surface that rises from the top of the wing just behind the spar. The surface creates turbulence behind it which effectively destroys the lift from the portion of the wing behind it. They are very useful when you want the plane to descend quickly (such as on landing or when descending from a too-strong thermal). Virtually every plane you build should have either flaps or spoilers. Having both is of no particular advantage.




tail feathers

The stuff at the back end of the fuselage: Vertical stabilizer, Rudder, Horizontal stabilizer, and elevator.


A pocket of warm air that lifts the plane. See section 3.2


A response that floored me was the one concerning reliance on timers. I have always felt that a good timer is very important to a good flight. Most of the good pilots I fly with share this opinion, but this seems to be an attitude limited to the East Coast. Pilots everywhere else opined that timers are just there to give time when requested. Get your heads out guys! A good timer can be very important! Starting at the winch, the timer can be a critical part of any sandbagging evolution. He can tangle the line, he can miss the hookup and send the winch line zooming down the field. He can forget his watch and have to run back to the parking lot to find it. He can fake a seizure. A good timer can delay a launch by as much as an hour if necessary. Once airborne, the timer can be the eyes in the back of the pilot's head. If he knows his stuff, and if the pilot trusts him, the timer can direct the pilot to areas of the sky that the pilot can not study. The timer can keep an eye on other competitors, and in general fill the pilot in on everything going on in the 80% of the sky the pilot can not watch. I have used information provided by a good timer to bail me out many times - I have myself bailed out many a pilot. In the closing minutes of a flight, the timer can keep the pilot out of trouble by properly directing him to and setting up the landing spot. The timer can advise of traffic launching, others landing, and in general help to avoid a midair. In the event of a direct attack on the pilot by another competitor's plane, the timer is expected to step up and take the hit, sacrificing himself to ensure a safe flight for the pilot.

A good timer will never cheat, but after the landing, he will stretch the tape as much as possible to get his pilot maximum landing points. To finish his job, a good timer will reliably return the pilot's transmitter to impound (making sure it is turned off), and he will turn in accurate and legible scores. The timer can do all this and also provide accurate and timely (no pun) time.

How to Choose a Good Timer. Here are a few pointers you can use to choose a good one:

1. Always pick a guy who has a digital watch. Guys with sweep second hands are not to be trusted and are generally crackpots lost in another era.

2. Always pick someone who can at least beat you as much as you beat him. This means Joe Wurts and Brian Agnew can only time for each other.

3. Never pick someone who has just had a bad flight or is having a bad day. Bad attitudes are infectious. Josh Glaab, the perpetual ESL Champ, and a past National Champ practically demands a psychological profile from his timers. "What did you have for breakfast?", "How have you been sleeping?", "Are you and your wife getting along?" "Any bad flights in the last week?"

4. Try to pick someone you know well and trust (who meets all the above criteria). A fellow competitor you fly with often, who knows your style, and who reads the time the way you like it is the best choice.

5. Never use your wife, a close relative, an employee, a sponsor, or a team member. You are setting yourself up for a lot of criticism. Use someone else's wife, especially if she is really hot, but only if she can read the air. Quite frequently the best timer is your closest competitor. Usually he will go out of the way to be helpful, and no one will ever accuse you of cheating.

6. No offense to the aged or infirm or handicapped, but never pick a timer with a stutter, a history of schizophrenia, a wooden leg or a heart condition, or who is restricted any way in his mobility. Sometimes timers have to be able to really move out, and of course having to wait 30 seconds to hear a 10 second countdown will really throw your landings off. Worse yet is getting two conflicting countdowns at the same time. Timers with multiple personality disorders are out. Listening to your timer argue with himself about who mother loved best will definitely throw off your flight.[16]

Tip stall

A stall on one wing tip only. This usually happens when turning slowly in a thermal. The inner wing tip is moving more slowly than the rest of the wing. If the rest of the wing is only slightly above stall speed the inner tip will stall first (assuming no washout). This causes the stalled wing tip to drop suddenly, pulling the rest of the plane with it. Tip stalls are easier to recover from than full stalls.


See winglets


trailing edge



Turbulators are very thin imperfections (i.e. a narrow piece of cellophane tape) intentionally added about an inch behind the leading edge of the wing to change the boundary layer. Ignore this stuff until you get some experience. This stuff is useful if you are trying to get the last 2% of performance out of your plane. Beginners are typically worried about getting the first 50% of the planes performance.

First, I'd like to say Hi to all as I just joined this maillist. I am a long time modeler and a real, honest-to-goodness aerodynamicist, so I'd like to throw in my two-bits.

Ah, the good ol' trip versus no-trip argument. Glad to see it still alive and 'tripping' =) For those of you who have it, and care for a bit of technical reading, peruse Soartech #8 and it should clear up many misconceptions. While Herk's statements are generally correct, I wanted to clarify a few points, and add some experiments that you can perform at home (with proper adult supervision =).

Laminar flow does have a tendency to separate easily when presented with an adverse pressure gradient, such as caused by the downslope on the aft end of the upper surface. By placing a turbulator (sometimes called a 'trip strip' because it 'trips' the laminar boundary layer making it turbulent), we can typically decrease this tendency to separate.

"...turbulating just before the place where the laminar separation would occur is the ideal situation." - Herk

The problem with this is that the separation point will vary with angle of attack, so you must ask yourself what range will be most useful. This may not be critical on most airfoils. There is no cut-and-dry solution, folks. Every airfoil, and indeed every airplane, is different. If you do not have the lift polars for a particular airfoil/Reynolds Number, your best bet is to get out and experiment. I start by placing a trip (2-3 layers of striping tape for a typical 2.5M size model) near the high point of the airfoil, or slightly ahead. Fly a couple times. Move it forward a bit.fly...note any changes. Keep doing this until you stop noticing improvements. This will be a good location =)

If you are trying to improve the performance of a stab, a good way of feeling it out is to try some hard pull-up/down (yes, you can improve your lift in both directions since most stabs are symmetric..just trip both top and bottom). If your stab is performing poorly, your pitch rate (or loop radius) will be limited by how hard the stab can pull (i.e., how much lift it can create). If you stall the wing, use less elevator input but be consistent for all trip locations. Your major drag here is caused by early separation, thus requiring more deflection to get the desired lift, so tripping should help, especially considering the Reynolds Numbers of the typical stab.

Wing performance is a little tougher as it may involve a big trade. While an airfoil may be very clean while cruising/hunting, when you get into lift and you pull more lift, you may start separating and killing yourself. So you turbulate, right? Another maybe. Depending on the conditions, if you spend more time cruising than thermaling (poor lift day), you probably shouldn't. Great lift day, do it. Also, remember that while launching we are pulling a lot of lift, so that comes into play. Once again, experiment.

Did this confuse everyone? There are no straight answers as the boundary layer is a fickle beast, especially at these LOW Reynolds Numbers. As noted by M. Selig in Soartech #8, two nearly identical airfoils that vary by only a few thousandths can have significantly different characteristics. And, personally, I don't know of anyone who can build that precise.[33]



A brand of foam friendly CA.



A launch system. A winch consists of a battery, motor, drum (spool), turn-around (pulley), parachute, and about 2000 feet of 200 pound test cord or fishing line. The drum is attached to the motor (often a Ford long shaft starter motor). The battery powers the motor through a foot switch. The cord runs out about 1000 feet to the turn-around (which is nailed into the ground) and comes back to the winch. A parachute is attached to the end of the line. At the top of the parachute is a steel ring. The ring is slipped over the towhook on the plane. The pilot steps on the foot switch causing the winch to start pulling in the line. The pilot waits until enough tension has built up in the line then throws the plane horizontally. The plane will almost immediately pitches up into a near vertical climb. The plane will arc up about 600 feet. During this arc the pilot will tap the foot switch to control the amount of tension on the line (the winch is capable of putting about 150 pounds of tension on the line). When the plane reaches the top of the arc the pilot will either stop tapping the foot switch and fly off the end of the line or stomp on the pedal and do a zoom launch. A zoom launch is very hard on the plane and not recommended for the beginner.

wind shear

The difference in the direction and speed of winds between one height and another.



They are only worth the effort if you can build them accurately and set them up at their optimum incidence angles. A winglet is not an addition to the end of the wing it is an integral part of it and needs to be designed as such.

The advantages are;

1. An effective increase in aspect ratio and dissipation of the tip vortex.

2. An increase in the effective dihedral. If you take a point about one third of the height of the winglet from the base that is the effective dihedral. This is why it is advisable to reduce the dihedral on the main panels of the Max flying wing, the winglets give it a huge dihedral.

3. Full size pilots report an improvement in handling at low speed in the turns. This is probably due to "2".

The disadvantages are;

1. They hurt the performance at high speed if they are set up for low speed handling and vice versa.

2. If you do not build them right, and set them right, they just cause extra drag.

3. They are vulnerable in transit and during bad landings, but this can be overcome by taping them onto the wing tip.

Design Pointers

1. The transition of the wing into the winglet should be curved to transition the sections. Some winglets are completely curved.

2. For low speed the winglet should be set for about 1 degree of incidence (relative to the direction of travel). At high speeds this should be reduced to zero, or less. The obvious answer is to have a flap on the trailing edge of the winglet and set it for the speed of the model, but this has not to my knowledge been tried on full size aircraft (other than the SB13, but that is a swept flying wing), expect to see it sometime.

3. The winglet needs to have a proper wing section. I used SD7003 on the Max and that seems to work o.k. The need here is for a low drag section with some camber.

To sum up there are some theoretical advantages for TD but they are only going to be achieved with accurate building and setting up. Personally I restrict their use, on my designs, to flying wings. I did try a set a long time ago on a 2.5 metre model. They seemed to work o.k. One day I damaged one and did not have any more ammunition in the car so I took the other one off and carried on flying at 2.3 metres. The model flew much the same as before. It must be said that I feel that the winglets were not set up properly on this model.

Like all of these things give it a try, you never know what will work till you try it. At the very least it might make a difficult model into one with good handling, and that would be a bonus.

Just as an aside, winglets are very trendy on full size competition Sailplanes at the moment. When asked if they worked one pilot replied; "Well they certainly worked over my wallet."[9]

Had a Scientist friend out in NM experiment with tiplets. After about a year, he concluded they had little or no effect on Model Gliders. As a result, I've never messed with them. They sure look nice though.[34]

Properly designed and adjusted winglets on sailplanes do improve duration. I documented the improvement in an article in the May, 1980 issue of Model Aviation. This article was referenced in Martin Simons book, Model Aircraft Aerodynamics, Page 80. The article was also summarized in QFI (July, 1995 I think). The improvement is approximately equivalent to extending the wing span by the heights of the winglets. The toe-out angle must also be adjusted to give the maximum performance at any given airspeed. Performance improvement is on the order of 5 to 10 percent or about twice the estimated uncertainty of measurement. Performance was measured by the technique discussed by Don Edberg in the last issue of RCM and it took about 250 flights to get the necessary data. More data would have improved the uncertainty but I got tired of the experiment. By the way, I am still flying the original model used to perform the experiments back in 1979 when flying 2-meter and expect to fly it at the Nats this summer. The model is no longer competitive but then, neither am I. :-)

While on the subject, what is a tiplet? I never heard of tiplets until a year or so ago and have never seen them defined. Are they winglets, the small tip panels that are the current design fad, or what? Maybe some of the experts here on RCSE can give the answer. [35]

Fred writes: >>This is one thing I have always questioned. With airliners having exactly one flight profile, why do you see 6 airliners of the same vintage have:

Up tiplets

down tiplets

both up and down tiplets

25% tip chord tiplets

No tiplets<<

Good question. The truth is the benefits are often questionable or real small. Most aerodynamicists believe the most efficient use of a winglet is to lay it down flat (increase the wing span). I am sure many will disagree, but the truth is most aerodynamicists would prefer the benefits of span over winglets. In fact the rule of thumb is 75 percent of the winglet length, used at extra span, provides the same benefits. Namely reduced induced drag. So why bother with winglets? Well larger aircraft like the MD-11, and Boeing 747 have huge wing spans already, and parking and taxing becomes a problem. I believe they use winglets up to 15 feet tall. Laying 75 percent of that length down flat would increase the wing span by 20 ft., and could present space problems. The other major issue is fashion. Yes, that's right fashion and trends are a major part of airliner design. (kind of like Kevlar reinforced fuses) Winglets are definitely trendy, and appeal to the trendy biz. jet market. Oh well, these are my comments, I am sure I have offended some winglet designer somewhere.[29]

wing loading


Rotation about an axis perpendicular to both the fuselage and the wings.

zoom launch

A variant of a winch launch. In order to survive a zoom launch a plane must be very strong, capable of withstanding around 200 pounds pull on the towhook. In order to make use of the launch the ship must be very aerodynamic - able to go fast without losing energy to drag. Finally the pilot must be able to time his actions precisely. A zoom launch begins about half way up a normal winch launch. At this point the pilot holds down the foot peddle to build up tension in the line. As the plane reaches the top of the arc the pilot points the plane straight down and continues to hold down the foot peddle. The combined pull from the winch and the stored tension in the line quickly accelerate the plane to very high speed. The pilot pulls up hard (the plane undergoes maximum strain), releases the foot peddle and the plane comes off the parachute nearly simultaneously. The plane now climbs straight up with all the speed generated in the dive. As the plane slows down the pilot pushes over into horizontal flight. Depending on the skill of the pilot and other factors, the plane should end up 100 to 200 feet higher than it would have without the zoom. A poorly executed zoom will result in the plane lower than it started, or the shattered remains of the plane fluttering to earth.

10.0 Miscellaneous

10.1 Manufacturers

10.1.1 Airtronics

10.1.2 Futaba

10.1.3 Goldberg

10.1.4 Great Planes

10.1.5 Hitec

10.1.6 Hobby Lobby

10.1.7 JR

10.1.8 Northeast Sailplane Products (NSP)

10.1.9 Tower Hobbies

10.1.10 WACO

10.2 The big names

10.2.1 Joe Wurts

10.2.2 Daryl Perkins

10.2.3 Dr. Michael Selig

Dr. Selig has been designing airfoils for sailplanes ever since he was an undergraduate student at the University of Illinois. He continued his work while doing graduate work at Princeton. The results of these studies were published in Soartech 8 in 1989. Airfoils such as the popular SD7037 were developed and tested at Princeton. After receiving his Ph.D., Mike returned to the University of Illinois to teach. Soon after returning to UIUC, Mike set up another test program for model airfoils. Soartech Publications published the first in a series of reports on the UIUC tests last year and I understand that the second report should be published shortly. Both reports are available from Soartech Publications, 1504 N. Horseshoe Circle, Virginia Beach VA 23451, USA.

Mike established a fund to continue the wind tunnel testing of model airfoils in UIUC low speed wind tunnels. These tests are funded by contributions from both modelers and the model industry. All contributions, no matter how small, will help to fund further research. I always enclose the following message with all Airfoil Plot and Model Design programs I sell. It gives the essential information needed to make a contribution.

The Selig and Selig Donovan airfoils included with this program are provided courtesy of Mike Selig. Many of these airfoils were developed by Mike and tested in the Princeton University wind tunnel back in 1987. Mike has started a new program to develop more airfoils and needs your support to keep it going. If you would like to see more airfoils developed and tested, please consider a contribution.

Contributions can be mailed to:

Prof Michael Selig

Dept. of Aeronautical and Astronautical Eng.

University of Illinois at Urbana-Champaign

306 Talbot Laboratory, 104 S. Wright St.

Urbana, IL 61801-2935

(217) 244-5757

Please make checks payable to "University of Illinois, AAE Dept." Also please write on the check "Selig - Wind Tunnel Testing/AAE Unrestricted Funds," and provide a letter stating that your contribution is to be used by Prof. Selig and his group of students (both undergraduate and graduate) in support of the airfoil wind tunnel tests.

More information can be obtained from Mike's web site at http:/wxh.cso.uiuc.edu/~selig

P.S. I first met Mike when he was a high school student and came to Tullahoma to fly in a contest I was CDing. He was a winner even then.[35]

10.2.4 Dr. Eppler

10.3 Addresses

10.3.1 Snail mail & phone numbers

The sources for obechi that I know about are:





Phone (509) 548-5201.

2) Kennedy Composites, Flint, Texas.

Phone (903) 561-3453.

3) Slegers International, Wharton, New Jersey.

Phone (201) 366-0880. Carries Kennedy material.

4) California Soaring Products, Covina, California.

Phone (800) 520-SOAR. Carries Kennedy material.

5) RA Cores, Southbridge, Massachusetts.

Phone (508) 765-9998.


10173 St. Joe Road

Fort Wayne, IN 46835

Building a pod-and-boom HLG? I just stumbled across a really neat catalog from Into The Wind Kites. Into The Wind in Boulder, CO. has a large selection of glass and carbon fiber rods and tubes, along with other fiddly bits of use to homebrew builders. I thought the catalog prices were quite reasonable. Some of their big-time kite winding spools might work for F3J, too. Oh, yeah, the kites are really nice, too! :-) Mark Suszko

Phone 1-800 541 0314 Mon to Fri 9-6, Sat 9-4 Mountain Time. For international orders call 303 449 5356. Fax 303 449 7315 anytime.

> The Voyager by K.& A. in Albuquerque was reputed by Jimbonee@aol.com to be the best plane for a Speed 400 in the world. Does anyone out there know who K. & A. is and how to get in contact with them? TIA

K&A can be reached at 9300 Yvonne Marie Dr NW, Albuquerque, NM 87114, (505) 890-7549, -7532 FAX. Ken Williams is not on-line yet, I believe. Could be wrong.

In addition to the Voyager designed for the Speed 400, Ken is producing two HLGs that are absolutely first rate quality.

- Quest HLG: balsa/foam wing, SD7037, polyhedral, R/E, available with wood fuse ($40) or glass fuse ($70) - Ken's glass work is impeccable.

- Request HLG: V-tail, ailerons, also SD7037, same prices as above.

Airtronics Inc.

15311 Barranca Parkway

Irvine, CA 92718

(714) 727-1474

(714) 727-1962 Fax

M&M glider tech

(310) 923-2414

P.O. box 39098

Downey, CA 90239.

Ken Williams

K&A Models

9300 Yvonne Marie Dr NW

Albuquerque, NM 87114


10.3.2 E-mail

Aerospace Composite Products

GSPARR@aol.com - -George Sparr


mac@anabat.com - Mac Davis; complete line of Slope Soaring Anabats (tm)

Airfoil Plot Program & Model Design Program Software

canders@edge.ercnet.com; 73757.1144@compuserve.com - Chuck Anderson

Alburquerque Soaring Association (ASA), New Mexico

havey@plk.af.mil - Mike Havey

AMA Headquarters


AMA District 2 Rep.

jrs@eng.buffalo.edu; 70672.2076@compuserve.com - Jim Sonnenmeier; F3B Team Selection Committee

Archaeopteryx Avion Associates

jimealy@peddie.k12.nj.us; jimL43@aol.com - Jim Ealy; Specializing in 1/6 to 1/3 scale plans and kits (glass and/or balsa) of vintage gliders.


sag@ozemail.com.au, 100241.2377@compuserve.com - Stephen Gloor; F3J and F3B interests

B2 Streamlines

bsquared@halcyon.com - Bill & Bunny Kuhlman; RCSD On The Wing flying wings columnist

Baltimore Area Soaring Society (BASS)

sjpbass@aol.com - Steve Pasierb, Editor; the AMA's first ever Gold level Leader Club.


cmarson@ibl.bm - Christopher Marson

British Association of Radio Controlled Soarers (BARCS)

Brian@skyquest.demon.co.uk - Brian Pettitt; Membership secretary; Thames Valley

Silent Flyers (TVSF), newsletter editor, UK

British Association of Radio Controlled Soarers (BARCS)

100307.522@compuserve.com - Jack Sile; editor; CIAM Flyer, editor, Thermal Talk

Newsletter (F3J Euro League) editor; QFI and Silent Flight articles


75113.547@compuserve.com - Pete Marshall; slope soaring contact

BS Engineering

Gavin_Botha@QMGATE.ARC.NASA.GOV - Gavin Botha; specializing in F3B products

(winches and line right now, more to follow)

Byers, Will

wilbyers@aol.com - Slope Soaring columnist for Model Aviation

CAB Design

cabdesigns@aol.com,Corndogger@aol.com - Chris Boultinghouse; makers of the Corn

Dogger HLG and sp400 WW2fighter series (all composite).

California Slope Racers (CSR)

NoProp@aol.com - Gerry Bohne, Treasurer

California Slope Racers (CSR)

ndawind@aol.com - Scott Tooher; President.

CANADA, Ottawa, Ontario

gerry.bower@crc.doc.ca; 73060.1022@compuserve.com - Gerry Bower, LSF contact

Central Arizona Soaring League (CASL)

buckets@aztec.inre.asu.edu - Vern Poehls

Cermark Electronics and Models

Stevenchao@aol.com - Steven Chao

Coffee Airfoilers, Tullahoma, Tennessee

jclogan@edge.ercnet.com - Craig Logan; Club Secretary


compufoil@aol.com; 75341.356@compuserve.com - Eric Sanders; Software author for

airfoil template plotting/modification

C.R. Aircraft Models contact

pnaton@psy.ucsd.edu - Paul Naton

Dayton Area Thermal Soarers (DARTS)

bob_massmann@milacron.com - Bob Massmann; Glidelines newsletter editor, National Soaring Society-Special Interest Group to AMA, President, editor and publisher of Sailplane-the journal of the NSS

Debs, Ray

raydebs@aol.com - Cml Glider, RC Pilot, Moni Motorglider (N91DG)

Dignan, Andrew

dignan@one.net - MAC software author for wing plots and foam wing cutting machine

Dodgson Design Kits

dodgsonb@eskimo.com - Bob Dodgson

Dynamic Modeling

edberg@netsun.mdc.com - Don Edberg; Radio Control Modeler Soaring Columnist;

F3B Team Selection Committee District X Representative; Team Kaos member.

Eastern Soaring League (ESL)

BadIdeas@fred.net - Jack Cash, President; JerseyBill@msn.com - Bill Miller, Secretary; sanctions 14 annual regional contests (28 contest days) from Mass. to Virginia.



FAI S8e RC Rocket Gliders contact

kwn@ieain.att.com - Kevin McKiou

FAI USA Soaring Representative

tedmonds@icaen.uiowa.edu - Terry Edmonds

Florida Soaring Society

MBrungar@gnv.ms.ch2m.com - Martin Brungard; secretary/scorekeeper

Gainsville Area Soaring Society (GASS)

gass@afn.org Gainsville, FL - Greg Cheves

Garwood, Dave

garwood@logical.net, 70254.361@compuserve.com - Dave Garwood; RC Soaring columnist at Model Aviation

GERMANY, Nauheim (near Frankfurt)

hermann@frust.enet.dec.com - Joe Hermann, Interests: Slope Soaring, HLG,

building _light_ _and_ strong, computerized foam cutter (planned).

Geuy, Tim

tim_geuy@ins.com - Slope Racing, F3B, KAOS team member.


farzu@uvg.edu.gt - Frankie Arzu; Club: Asociacion Guatemalteca de Aereomodelismo


Harbor Soaring Society (HSS), Costa Mesa, CA

yasmarnod@aol.com - Don Ramsay

Harbor Soaring Society (HSS), Costa Mesa, CA

RLackey@aol.com - Roger Lackey; President; International F3J competitor

Hobbico Product Support

74641.3060@compuserve.com - Distributor for Great Planes, O.S., Supertigre, Hobbico, Duracraft, Kyosho, Duratrax, Helimax, Flitecraft.

HOLLAND, Uithoorn.

Jeffrey_brunet@vnet.ibm.com - Jeff Brunet. Member of the Hoofddorpse Luchtvaart Club. Soaring and Slope soaring interests.

Ingraham, Doug

dpi@lofty.com, 75116.473@compuserve.com - speed controls for electric sailplanes

Intermountain Silent Fliers (IMSF), Utah

dale@novell.com - Dale Taylor

Intermountain Silent Flyers (IMSF), Salt Lake City, Utah

krogers@xmission.com - Keith Rogers; Vice President

Intermountain Silent Flyers (IMSF), Salt Lake City, Utah

oakley@xmission.com - Tom Hoopes; manufactures misc. electronics for soaring (Mini-Mix onboard mixers, thermal sensor, cycler/peak charger.


lk1boq75@icineca.cineca.it - Aldo Toni; Aereoclub Bologna-Italy; FAI #8889

Ivinghoe Soaring Association, United Kingdom

dwoods@cix.compulink.co.uk - Graham Woods; club newsletter editor

Ivinghoe Soaring Association, United Kingdom

john@omsys.demon.co.uk - John Wheatley


ken.ueyama@iac-online.com (Ken Ueyama); F3B and F5B interests

Lachowski, Mike

mikel@airage.com - Soaring Columnist for Model Airplane News, Radio Control Soaring Exchange List keeper (soaring-request@airage.com, type "subscribe"; listserver: soaring@airage.com)

Las Vegas Soaring Club (LVSC), Las Vegas, NV

71161.3275@compuserve.com - Steven Smith

League of Silent Flight

73027.520@compuserve.com; CalPLSF@aol.com - Cal Posthuma

League of Silent Flight

stumpglide@aol.com; 73024.1046@compuserve.com - Mike Stump; LSF President;

Nationals Entries for LSF/AMA Nats, Muncie 1995

Lincoln Area Soaring Society (LASS), Nebraska

sdworsky@ltec.net - Steve Dworsky; newsletter editor

LJM Associates

74724.65@compuserve.com - Lee J. Murray; PC-Soar software; Valley Aero Modelers,

Appleton, Wisconsin

Memphis Area Soaring Society (MASS); North Alabama Silent Flyers (NASS),


75227.3066@compuserve.com - Loren Banko

Mid-Pacific Soaring Society (MPSS), Hawaii

mytai@aloha.net; 70751.3524@compuserve.com - Adrian Kinimaka

Minnesota RC Soaring society (MRCSS)

tmrent@goldengate.net - Tom Rent

Model Construction Videos

72351.2367@Compuserve.com - D. O. Darnell; Tulsa RC Soaring (TULSOAR), Tulsa, OK


dv28320@sysh.fokker.nl; 101323.2330@compuserve.com - Theo Volkers

Interests: F3b, Aerodynamics.

NEW ZEALAND, Christchurch

griff@chch.planet.co.nz - David Griffin; Interests F3B, Thermal Duration, slope racing, HLG. Partner in Canterbury Sailplanes, manufacturing F3B and Thermal models.

North Alabama Silent Flyers (NASF)

stgermai@pentagon-hqdadss.army.mil - Ron Swinehart, President.

North Atlanta Soaring Association (NASA), Atlanta, Georgia

tfoster@america.net - Tim Foster; past and present President

Northeast Sailplane Products

salnsp@together.com; salnsp@aol.com; 76655.2140@compuserve.com - Sal DeFrancesco


Inge.Balswick@ST.Notes.Telemax.NO - Inge Balswick; F3J Coordinator, Cirrus RC Soaring Club, with center in Norway's capital, Oslo; Cirrus RC Soaring Club WWW

HomePage - http://www.powertech.no/~ingeb/cirrus.html

OHIO, Cincinnati

mike.welch@sdrc.com - Mike Welch; hand launch contact

OHIO, Cleveland

76503.2002@compuserve.com - Tom Lipovits

OHIO, Columbus

doerr.3@osu.edu - Rick Doerr, Mid Ohio Soaring Society (MOSS)

OHIO, Columbus

tomnagel@freenet.columbus.oh.us - Tom Nagel, Mid Ohio Soaring Society (MOSS)

OREGON, Medford

justpfun2@aol.com - Jerry Miller; Southern Oregon Soaring Society (SOSS)

Orlando Buzzards, Florida

76054.1200@compuserve.com - Rick Eckel

Pasadena Soaring Society (PSS), Pasadena, CA.

70541.2160@compuserve.com - Matthew Orme

Pasadena Soaring Society (PSS), Pasadena, CA

70412.2423@compuserve.com - Paul Trist; President

Phelan, Dennis

74344.2263@compuserve.com - F3B Articles author; District 1 representative of the F3B TSC.

Pikes Peak Soaring Society (PPSS), Colorado Springs, CO

gregt@col.hp.com - Greg Tarcza; President.

Portneuf Pelicans, aka Southeast Idaho Soaring Association

shamim@math.isu.edu - Shamin Mohamed; WEB page-http://math.isu.edu/~shamim/

Portland Area Sailplane Society (PASS), Oregon

patch@sequent.com - Pat Chewning; Secretary

Pratt, Doug

76703.3041@compuserve.com - Chief Sysop, Compuserve Modelnet Soaring Forum

RA Cores

racores@world.std.com - Jim Reith; Affordable, computer cut, custom foam wing cores by modelers, for modelers; Southbridge, MA

RC Online

jfesta@cs.uah.edu - Jerry Festa; Sport Flying columnist

RC Online electronic magazine

rconline@rolix.com - Randy Mullins; Editor

RC Soaring Exchange

soaring@airage.com - RC soaring listserver from Air Age, publishers of Model Airplane News, Mike Lachowski list keeper; to subscribe send email to soaring-request@airage.com

Redwood Soaring Association, Eureka/Arcata, CA

zerdo@aol.com - Jess Walls

Rocky Mountain Soaring Association (RMSA), Denver, Colorado

bpederson@ball.com; 73542.1400@compuserve.com - Robert Pederson

Sacramento Valley Soaring Society (SVSS), CA.

74642.1507@compuserve.com - James Dudley; club newsletter editor

Seattle Area Soaring Society (SASS), WA

QBUQ79A@prodigy.com - Joseph Conrad

Seattle Area Soaring Society (SASS), WA

waidr@aol.com - Waid Reynolds, newsletter editor

Seattle Area Soaring Society (SASS), WA

lsf5@lsf5.seanet.com - Jim Thomas

Seim, Steven

sseim@microsoft.com; 74441.2516@compuserve.com - Composite fabrication, CAD, CNC, at Microsoft Corp.

Selig, Michael

UIUC Airfoils, WWW site: http://uxh.cso.uiuc.edu/~selig

Silent Knights Soaring Society (SKSS), Newark, Delaware

kirchste@omni.voicenet.com - John Kirchstein; Vice President, newsletter editor

Silent Knights Soaring Society (SKSS), Wilmington, Delaware

lisansky@strauss.udel.edu - Terry Lisansky

Smith, Scott

scott@stateoftheart.com - RC soaring handlaunch columnist for Radio Control Soaring Digest

Soaring Stuff Distributor

collinst@ios.com; gliderguy@aol.com; 72610.26@compuserve.com - Taylor Collins

SoarTech Reference Journals

herkstok@aol.com - Herk Stokely

SOUTH AFRICA - Atlantic Flying Club, Cape Town

stevemac@iaccess.za - Steven McCarthy

SOUTH AFRICA - Kyalami Radio Gliders

coetzeea@data.co.za - Anton Coetzee; Chairman; F3B, F3H, 60" slope racing, HLG, Thermal duration, PSS, F5D, etc.; Composite fabrications, tooling, foam cutting, various composite kits available.

SOUTH AFRICA - Kyalami Radio Gliders

marks@iafrica.com - Mark Stockton; Thermal Competition, F3J, F3B, HLG, 2 Meter Soarers and F5D.

SOUTH AUSTRALIA - Southern Soaring League (SSL)

pfe@celsius.oz.au - Paul Ferguson; Airborne Magazine Soaring columnist

Southern Arizona Gliders and Electrics, Inc. (SAGE) club contact, Tucson,


74001.3712@compuserve.com - Bill Melcher

Southern Arizona Gliders and Electrics (SAGE), Arizona

imdouglas@ccgate.hac.com - Ian Douglas

SR Batteries

74167.751@compuserve.com - Larry Sribnick-President; Flying Models Magazine; Electric Columnist; National Electric Aircraft Council (NEAC) Chairperson; AMA

District 2 Electric Contest Board Representative; AMA District 2 FAI Electric Team and Site Selection Committee Representative

SR Batteries Tech Services

76035.544@compuserve.com - Stephen Anthony

St. Leonard Shores Sailplane Association, Maryland

73437.1044@compuserve.com - Bob Heisner; President

Storm King Soaring Team (SKST), New York

75561.753@compuserve.com - Kurt Zimmerman; Vice President; Sussex Thermal Sniffers; Orange Co., New York sites

Studio `B' (Home of the Stingwing, Blue Max combat sloper, et al.)

Lex Liberato studiob@aloha.net


taucom@kaiwan.com; 73617.1731@compuserve.com - Manny Tau; California Slope Racers, newsletter editor; Torrey Pines Gulls, San Diego, CA.; Team

Kaos member.

Tidewater Model Soaring Society (TMSS), Richmond, Virginia

dugbarry@aol.com - Doug Barry; Life member of AMA, LSF Level 5, CSS Diamond

TEXAS, Sugar Land

thrasher@sugar-land.dowell.slb.com - Bob Thrasher

Torrey Pines Gulls (TPG) and Torrey Pines Scale Soaring Society (TPSS),

San Diego.

dhuggard@cts.com - Doug Huggard


waco@ari.net - Weston Aerodesign

Westreich, Andrew

ajw@apollo.mayo.edu - PC based airfoil/wing plotter distributed free over the net along with a database of airfoils taken from UIUC.

Winch doctor

winchdoc@aol.com Sal Peluso of San Diego builds custom winches and sells other winch related stuff.

Wurts, Joe

jwurts@ladc.lockheed.com - Past F3B World Champion; Current U.S. Soaring (F3B) Team member; RC soaring pilot extraordinaire

Young, Pete

youngpw@indirect.com - RC Reports Soaring Columnist

o _ o/ _ o

o/__ / | / __/

_|__(__/_|__/___|___/ /o


Manny Tau WH6OQ |

taucom@kaiwan.com /o


10.3.3 Web sites


a free R/C classified ad service


The Hitec RCD home page


Sheldon's hobbies home page


Tower hobbies website


RC Modeler Magazine


Sal-Northeast Sailplane Products



Go to URL:


Fill in the form to look for:

RC + Soaring


R/C + Soaring

Last week it returned over 1000 documents that matched this search.

Fred Mallett

Here's my list - many overlaps with Brian's list posted yesterday:

Search engines


rc soaring pages:

http://homepages.enterprise.net/aeolus/index/index.html Aolus (G Woods)

http://www.traplet.co.uk/traplet/ online mag

http://imt.net/~ims/scale.html scale stuff - catalogue

http://dutlhs5.lr.tudelft.nl/ Delft University of Technology

Http://www.pncl.co.uk/~coppice/barcs.html BARCS www page


http://www.kaiwan.com/~markle/number1.html (soaring pics)

http://www.netads.com/~cabdesigns/ CAB Designs

http://www2.ari.net:80/home/waco WACO web page

www.towerhobbies.com Tower Hobbies web page

http://www.primenet.com/~trippin/cr1.html CR web site

http://www.powertech.no/~ingeb/cirrus.html Cirrus RC Soaring Club WWW


http://rvik.ismennt.is/~agbjarn/thytur-2.html homepage Icelandic


http://www.ar.com/ger/rec.models.rc.html green eggs report

http://www.ar.com/ger/ general green eggs report

http://www.mat.uc.pt/~pedro/ncientificos/Software.html plotfoil and flight


http://world.std.com/~racores/ RA Cores -


http://www.mat.uc.pt/~pedro/ncientificos/RConline.html rc online or

http://alpha.smi.med.pitt.edu:9000 maybe new site?

"Microlift and thermals close to the ground" at:


"Slanted: thermaling patterns on windy days" at:


http://rampages.onramp.net/~micheleb/hanger.html Michelle's Hangar:

airfoil plotting s/w and other stuff


http://www.cudenver.edu/~ltrujill/RC/ 'Silent Satisfaction'

soaring page

http://www.mediom.qc.ca/~lcimon/planeur.htm canadian soaring web page

http://www.nesail.com North East Sailplanes home page

http://www.cursci.co.uk/rc-soar/index.htm Beacon newsletter or:

http://biomednet.com/rc-soar/index.htm new address

http://www.ddave.com/ soaring info and link to composites


http://aero.stanford.edu/OnLineAero/OnLineAero.html Aeronautical theory

in digital textbook

http://uxh.cso.uiuc.edu/~selig UIUC (Selig) web site

http://biomednet.com/rc-soar/index.htm RC Soaring Web Page

http://www.alpes-net.fr:80/~obordes/ French F3F/sites etc.

http://ourworld.compuserve.com/homepages/gbongartz G Bongartz web page


http://www.earthlink.net/~jaffee slope & power page

http://www.rcsoaring.com AMA soaring page

http://www.paranoia.com/~filipg/HTML/FAQ/BODY/F_Battery.html battery info

http://uxh.cso.uiuc.edu/~selig/ selig web site


http://grads.iges.org/pix/euro.fcst.html Medium Range

Forecasts for Europe (US: NCEP)

http://www.dkrz.de/ecmwf/ecmwf.html ECMWF Forecast Images

(Europe medium range forecasts)

http://www.meto.govt.uk/cgi-bin/Inshore UK Inshore Waters Forecast

http://www.meto.govt.uk/cgi-bin/Offshore UK Shipping Forecast


If you want an excellent Web site containing a wealth of Aerodynamic Information try the Stanford University Aero/Astro site. It has wing design theory, airfoil design, as well as various design programs, including wing design, in simple language. You can reach the Stanford home page at http://www.stanford.edu Then go to the Aero/Astro department an look around. [29]

http://www.tminet.com/cst Composite Structures Technology (CST)[52]

10.4 Publications

10.4.1 Model Airplane News

10.4.2 Model Aviation

10.4.3 Radio Control Modeler (RCM)

10.4.4 Radio Control Soaring Digest (RCSD)

RCSD is a magazine published from Wylie Texas, whose

Editors email address is RCSDigest.

RCSE is a mailing list located at soaring@airage.com that is

supported by the Model Airplane News magazine.

(And the soaring editor, Mike Lachowski)

RCSD's full name is R/C Soaring Digest, it is a black and white 5"x9" monthly magazine that covers silent flight type articles. There are some electrics, but mostly soaring. It is $30/year for first class postage, price varies if your country does not have Bill Clinton as its president.

R/C Soaring Digest (USA)- R/C Soaring Digest, P.O. Box 2108, Wylie, TX. 75098-2108 phone(214) 442-3910 fax(214) 442-5258 subscription price $30.00 per year (12 issues)

10.4.5 Quiet Flight International (QFI)

Quiet Flight International (UK)- Traplet Publications Limited, P.O. Box 167, Florham Park, New Jersey 07932 fax(201) 765-0881 subscription price $30.00 per year (6 issues), $58.00 two years (12 issues) Traplet Publications Homepage- http://www.traplet.co.uk/traplet/

10.4.6 Sailplane Modeler

Sailplane Modeler (ex Scale Slope FAI & Thermal) (USA)- Sailplane Modeler, P.O. Box 4267, W. Richland, WA. 99353 phone(509) 627-0456 subscription price $19.95 per year (4 issues) Sailplane Modeler Homepage- http://www.sailplanemodeler.com

10.4.7 Silent Flight

Silent Flight (UK)-U.S. agent- Wise Owl Worldwide Publications, 4314 West 238th Street, Torrance, CA. 90505-4509 phone(310) 375-6258 fax(310) 375-0548 subscription price $35.00 per year (6 issues)

10.5 Books

Composite Construction for Homebuilts, Ultralights, & ARVs, $19.95.

Radio Control Foam Modeling, $15.95.

Designing and Building Composite R/C Model Aircraft: Foam, Fiberglass, and the New Plastics, $16.95.

All three of the above books are good, but "Radio Control Foam Modeling" (often called "Foam Modeling") has the most useful information. The other two (written by Jack Lambie) are also very good but a bit dated.

"Radio Control Foam Modeling" is an Argus book and I've seen it advertised in RCM and Model Builder and Flying Models. It discusses tools, template making, core cutting, vacuum bagging, and repair. This one is the slammy (that's good). It focuses on creating tools instead of running out and spending gobs of money (EDITORIAL NOTE: anybody notice that the UK books and publications seem to focus a lot more on DIY as opposed to GOBs [Go Out and Buy it] compared to most of our US publications? Whatever happened to good ole American Ingenuity?).

"Designing and Building Composite R/C Model Aircraft" I think is out of print but has a good discussion of design and a wonderfully simple definition of lift (Lift is the resultant force in the opposite direction of pushing air down {or which ever way your forcing the air}) Again, some of the techniques are sort of dated or just downright wonky {use a vacuum cleaner to bag wings(?)} but its still worth reading IF you can find it (the Los Angeles public library has a copy (in fact they have quite a large collection of R/C modeling books).

"Composite Construction of Homebuilts,,,," is also good and has a very good discussion of materials and design. But best of all, a (still valid) list of resources and suppliers. This one is still available from Zenith Books

Add to this list Harry Higley's "Master Modeling" (available from RCM, MAN, and many hobby shops) and your at least able to follow these guys' conversation if not construct a decent wing (and fuse). Hope this helps!

10.5.1 Model Aircraft Aerodynamics by Martin Simons

published by MAP, Argus Books Limited, ISBN 0 85242 441 8.

10.5.2 Stick & rudder by Wolfgang Langerswitz

10.5.3 Tailless Aircraft in theory and practice by Nickel and Wohlfahrt

10.5.4 The old buzzard's soaring book

Get OLD BUZZARD'S SOARING BOOK by Dave Thornburg (16.95 postpaid from Pony X Press @ 505-299-8749). It is THE single best resource on thermals that I've encountered. It's done wonders for my flying. The video is entertaining, too. A second source I'd recommend was an article by Joe Wurts on a relative-wind method of finding thermals, but I forget when/where I saw it. Dave Garwood did publish a pretty good summary of that subject in the Soaring column in Model Aviation that discussed HLGs, May 1996.

10.6 Legal considerations

10.6.1 FCC

10.6.2 FAA

F.Y.I. - Controlled Airspace Considerations for RC Aircraft.

If your club is looking for a new flying site, there are many restrictions that will influence the number and location of possible flying sites. These restrictions are typically the location of other clubs flying RC aircraft, site access, cost of owning/maintaining a particular site, and neighboring land use. From recent experience it is a good idea to get hold of a aircraft navigation charts of your area to see if there may be restrictions on the airspace above the site. AMA rules state that RC aircraft should be flown no higher than 400 feet above ground surface within 3 miles of an airport without notifying the airport operator. However, abiding by this rule alone may not be enough.

Earlier this year the club I fly with, the Michigan International Soaring Society (M.I.S.S.), lost it's primary flying site. M.I.S.S. is one of two sailplane clubs in the greater Detroit area. We began our search for favorable locations in areas where we knew radio interference from other clubs was not going to be a problem. Several prospective sites were located. Almost as an afterthought, I decided to check out these locations relative to airports on a Detroit sectional chart (full-size aircraft navigation chart). Three of the sites, as well as the M.I.S.S. secondary flying site, were located within the area designated as Class B airspace (formerly known as TCA).

One of the prospective flying sites was within the inner area of the Detroit Metro Class B airspace, where the Class B airspace starts at the surface. The other prospective sites and the clubs secondary field were in the area where the Class B airspace began at 2500 ft.

The shape of Class B airspace has been described as an upside-down wedding cake. Within 10 miles of the airport it extends from the surface up to, say 8000 feet. From 10 miles to 20 miles it extends from 2500 feet to 8000 feet. From 20 to 30 miles from the airport it extends from 4000 feet to 8000 feet. The actual shape and size varies from airport to airport. Class B airspace is typically found around large airports such as Detroit Metro and Chicago O'Hare. According to the FAA regulations, any aircraft operating within Class B airspace must have a Mode C transponder and be in direct 2-way radio communication with the tower.

(Immediately, the debate raged as to how high can we fly our RC sailplanes and still see them? But that's another story...)

This prompted calls to the local offices of the FAA and Flight Standards (they develop the regulations that the FAA enforces). After an extensive search of the regulations they informed me that there are no regulations that specifically apply to the operation of RC aircraft in controlled airspace. To date there have been no incidents between full size aircraft and RC aircraft, therefore no regulations have been promulgated. So for now, and hopefully for a long time to come, there are no specific regulations regarding the operation of RC aircraft in controlled airspace.

But it is a grey area. It is quite possible for one to comply with the AMA requirements of being 3 miles from an airport and still be operating within controlled airspace. The FAA can't make you stay out of controlled airspace but they have made it quite clear that they don't want you there. And why go somewhere you're not wanted?

The FAA's chief concerns were that we do not know the altitude of our planes at any given moment and therefore can't tell when we are inside controlled airspace. More importantly, it is not possible for the RC pilot to be in direct contact with the tower. This means that the tower can't "shut us down" immediately if they need to route planes through the area we are flying. In other words, they won't have control over an RC aircraft in airspace where they have control over all other aircraft.

It is not difficult to imagine that problems could occur if a pilot on approach or departure sees something they don't expect to see (like a 1/4 scale glider circling upwards). This might result in the pilot taking some sort of action, such as aborting the landing. This would definitely get the attention of the FAA as well as the airline and could result in costs and publicity nobody wants.

Other controlled airspace such as Class C (formerly ARSA) Class D (formerly Control Zone) and Military Operations Areas (MOA) also need to be considered. The requirements for operating in Class C airspace are similar to Class B. For Class D airspace, authorization can be provided by the tower on a case by case basis. MOA's may only be active during certain hours of the day. Be sure when you refer to a sectional chart, that it is the current edition. These charts are updated periodically and the shapes and hours of operation of controlled airspace can change.

Another consideration offered by the folks at Flight Standards, was the sensitivity to local radio interference of full-size aircraft navigation equipment, such as omnidirectional and ILS beacons. When they are being inspected or serviced, the crews have be sure that there car/truck radios are turned off as they approach the beacons. No one seemed to know if RC radio's would cause interference, but it would be best to steer clear and avoid any problems.

The people I spoke with at the FAA and Flight Standards were very helpful. They really bent over backwards to track down the answers to my questions. They even provided suggestions for some potential flying sites. If you think airspace restrictions may be a problem with a current or prospective site, you should call them.[19]

10.6.3 Local laws

10.6.4 Liability

11.0 Bibliography

[1]  Murray Lane  PPSS  mlane@ford.com
[2]  Shamim Mohamed (shamim@math.Isu.EDU)
[3]  Larry Sribnick  SR Batteries  74167.751@compuserve
[4]  Aaron
[5]  Jim Bonk  75453.3135@compuserve.com
[6]  Ron Scharck     Scharck@aol.com
[7]  Ron C.
[8]  Tim Potts  TPOTTS1@aol.com
[9]  Dave Jones,  Editor QFI, qfidj@waverider.co.uk
[10]  Ian Douglas
[11]  Erik
[12]  John Roe  104200.740@compuserve.com
[13]  Art Reitsma    areitsma@island.net
[14]  Fritz
[15]  Martin Brungard mbrungar@gnv.ms.ch2m.com
[16]  Frank Weston  waco@ari.net
[17]  Thayer Syme  thayer@sirius.com
[18]  Aaron Valdes   avaldes@sdcc13.ucsd.edu
[19]  James Gell  james_w._gell@mclrnhrt.uucp.netcom.com
[20]  Gordon Jennings     GoMo@thegrid.net
[21]  Roger  
[22]  Blaine Beron-Rawdon  Envision Design  evd@netcom.com
[23]  Waid Reynolds
[24]  Dennis Weatherly  dennis_weatherly@MENTORG.COM
[25]  Tim Elliott   elliott_t@a1.wdc.com
[26]  Les Grammer  grammer@wsu.edu
[27]  Barry Ensten
[28]  Larry Hardin Research Engineer, Fluid Mechanics  hardin@lwhn.res.utc.com
[29]  Gavin Botha  Gavin_Botha@qmgate.arc.nasa.gov
[30]  Bill & Bunny Kuhlman      B2Streamlines      bsquared@halcyon.com
[31]  DAVE
[32]  John Kirchstein
[33]  John Duino   (jduino@netcom.com)
[34]  Lucas
[35]  Chuck Anderson  canders@edge.net
[36]  Walter Gomes    wgomes@earthlink.net 
[37]  Joe Wurts 103610.3507@CompuServe.com
[38]  Herk Stokley  HERKSTOK@aol.com
[39]  Dr. Richard C. Williamson    M.I.T.   williamson@ll.mit.edu
[40]  Dale Taylor    Dale@wordplace.com
[41]  Andrew  MacDonald
[42]  Oleg Golovidov  olgol@apollo.aoe.vt.edu
[43]  Anton Coetzee   FibreFlight Composites   coetzeea@data.co.za
[44]  Peter Bailey    baileyp@logica.com
[45]  John Mathews    High Country Soaring Society   jmathews@fastprint.com
[46]  Red S.    Red's R/C Battery Clinic    sau@hgea.org
[47]  Fred Mallett   FrederM@aol.com
[48]  Joe Hahn   DJ Aerotech  DJWerks@aol.com
[49]  Unknown
[50]  Roy Sakabu  roys@telerobot.com
[51]  Dan Gaudenti   gaudent@qnet.com
[52]  Matt Gewain  CST  mpg@tminet.com