Soaring FAQ (Frequently Asked Questions)

If you have an interest in Electric-assist soaring, or other electric-powered R/C models, check out the E-Zone, where you will find a FAQ and other information.

Last update to content on October 14, 1998.
Headers updated, and posted to kohlin.com, on July 23, 2002.

1.0 Introduction

2.1 Clubs

2.1.1 Local

2.1.2 AMA

2.1.3 LSF

2.1.4 Organizations outside the USA

2.2 What does it cost?

2.3 How long does it take

2.4 Choosing your first plane

2.4.1 Class restrictions

2.5 Radio equipment

2.5.1 Introduction & choosing the right radio

2.5.2 Transmitters & receivers

2.5.3 Servos

2.5.4 Batteries

2.6 Building your plane

2.6.1 General guidelines

2.6.2 Servo mounting

2.6.3 Tow hook mounting

2.6.4 Wiring

2.6.5 Visibility

2.7 Static plane trim

2.8 First flight

2.8.1 Special pre-flight

2.8.2 Normal pre-flight

2.8.3 Launch

2.8.4 Flight

2.8.5 Landing

2.9 Flight trimming

2.10 Repairs

2.11 Second plane

3.1 The plane

3.2 The lift

3.3 The ideal flying site

3.4 Launch methods

3.4.1 Hi-starts & bungee cords

3.4.2 Winches

3.5 Hand launch

3.6 Estimating distance

4.1 The plane

4.2 The lift

4.3 The ideal flying site

4.4 Launching

5.1 Flight plan

5.2 Turns

5.3 Circles

5.4 Thermal clues

5.5 Landing

5.6 Contests

6.1 Necessities

6.2 The well equipped workshop

6.3 Field box

6.4 Altimeter watches

7.1 Glues

7.1.1 Aliphatic glues

7.1.2 CA

7.1.3 Epoxy

7.1.4 Other

7.2 Woods

7.3 Fiberglass, Carbon Fiber & Kevlar

7.4 Built up construction

7.4.1 Advantages over composite construction

7.5 Composite construction

7.5.1 Advantages over built up construction

7.6 Wing incidence

7.7 Sheeting/covering wings

7.8 Hinges

7.9 Spars

7.10 Pivots, bell cranks, and control horns

7.11 Labels

7.12 Mixers

8.1 Introduction

8.2 Contest directors (CDs)

8.3 Thermal Duration

8.3.1 Launch order/windows

8.3.2 Pop-offs

8.3.3 Landing circles

8.3.4 Timers

8.4 Slope

8.4.1 Speed

8.5 Scoring

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

10.2.4 Dr. Eppler

10.3 Addresses

10.3.1 Snail mail & phone numbers

10.3.2 E-mail

10.3.3 Web sites

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)

10.4.5 Quiet Flight International (QFI)

10.4.6 Sailplane Modeler

10.4.7 Silent Flight

10.5 Books

10.5.1 Model Aircraft Aerodynamics by Martin Simons

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

10.6 Legal considerations

10.6.1 FCC

10.6.2 FAA

10.6.3 Local laws

10.6.4 Liability

Edited by Murray Lane

Contributed to by many readers of the RCSE

Revised September 19, 1996

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

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

2.1.1 Local

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

2.1.3 LSF

2.3 How long does it take

2.4 Choosing your first plane

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

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

2.5.2 Transmitters & receivers

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

2.5.3.1 Relative qualities of servos

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 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

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:

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

http://www.paranoia.com/~filipg/HTML/FAQ/BODY/F_NiCd_Battery.html

[42]

>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

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

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

2.6.4 Wiring

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

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

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 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

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. 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 wi 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

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

2.8.5 Landing

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 woul 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 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

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

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

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 collisio 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 faste

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.

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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 (the difference between the winds at one height and another) 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

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

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

[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, whil 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

4.0 Slope soaring

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,

4.2 The lift

4.3 The ideal flying site

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

5.1 Flight plan

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

5.4 Thermal clues

5.5 Landing

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

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

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

7.1.1 Aliphatic glues

7.1.2 CA

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 a kicker 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.

7.1.2.1 Health concerns

7.1.3 Epoxy

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]

7.1.3.1 Health concerns

"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

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

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:

Balsa: 0.14,

Spruce: 0.23,

Obechi: 0.32,

Kevlar in Epoxy: 0.40,

Uni S-glass in Epoxy: 0.79,

Uni Carbon in Epoxy: 1.0.

(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

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

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

Yes

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

Don't.

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,

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