COVERING AND FINISHING

IMPORTANT:
Don't skip covering the fuselage and tail just because they are solid wood. Painting them without covering first is not enough. They will be much more resistant to splitting and breaking on hard impacts if they are covered with something - Sig Silk, Silkspan, Sig Silray or iron-on covering material.
The manufacturer's directions for applying iron-on coverings are packed with the material. Follow these closely, for different types of covering have different iron-on temperatures and techniques of application.

Whatever kind of covering you desire to use, it will not conceal a rough framework. Sand carefully with fine sandpaper before beginning to cover.

Covering With Silk, Silkspan, or Silray

Although we refer to silk in the directions, all of these coverings are applied wet in the same manner as follows:
Brush an unthinned or very lightly thinned coat of clear Sig Supercoat or Sig Lite-Coat Dope over all parts of the framework that will contact the covering. When dry, resand with fine sandpaper, to remove any fuzz or raised grain. Brush on a second coat and sand again.

The bottom of the wing is a good place to start covering. Cut a piece of material about 1/2" larger all around than half of the wing, with the grain running lengthwise. (The grain of woven materials runs parallel to the finished bias edge.) Some builders next dip the piece in water and apply it to the wing. I find that the silk sticks together and takes a lot of pulling and smoothing to get it in place so we do it a bit differently as shown in the photo.
Pin the dry covering in place and "paint" the water on with a brush.
Go around the edges, pulling out wrinkles and stretching the material smooth. You need not pull it up drum tight, in fact going to this extreme is not advisable. Just pull out all of the wrinkles. Use pins, if necessary, to hold the silk smooth, though wet silk usually stays in place without too much pinning. We like to fasten one end - in this case the center joint of the wing - pretty firmly with pins so that you can pull against this anchored end in stretching the silk the long way.




Brush around the outside edge of the stretched silk with clear dope. The dope will soak through the material and adhere to the dope already dried into the framework. Allow to dry.
Trim off the edges with a sharp blade. We find that a thin double-edged razor blade is ideal for this, but a single-edged blade does okay and you can't cut your fingers on it. On the bottom, trim off flush with the wing all the way around. Go over any rough areas or places that have not stuck down properly with more dope and press the loose spots down as the dope is drying and getting stickier.
The top half is done in identical fashion except that the silk should be brought down over the edges instead of being trimmed off flush. On the front, lap the silk over the edge of the bottom, over-lapping about 1/8". At the back, bring the material down over the back edge of the trailing edge but do not lap it over the bottom covering.
Use the same process on the tail section and fuselage.



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Allow the water to dry out of the wood before applying the first full coat of clear dope. Apply 3 or more coats of clear dope. Sand with 220 3M Tri-M-Ite or other no-load paper. Keep in mind that extra coats of dope will add weight. Sig Lite Coat clear dope may be used in place of Supercoat Clear if desired. It has low shrink characteristics and is less likely to warp.

Three coats of clear should provide a good base for color. Sand lightly when dry with 220 grit 3-M Tri-M-Ite no-load paper. The color dope may be brushed or sprayed.

Supercoat Color Dope should be thinned with 10% or more Supercoat Thinner for brushing. This helps prevent brush marks and gives smoother coats. Flow on wet coats and avoid rebrushing back over an area already painted. For spraying, thin dope about 50 - 50. Add more thinner if the dope does not go on evenly.

If high humidity causes the dope to "blush" or turn white, the test way to handle this problem is to wait until the humidity situation improves and apply another coat of dope. This will eliminate the blush. If it is necessary to dope during high humidity, Sig Retarder may be used in place of part of the Supercoat Thinner (amount depends on the humidity) to reduce the tendency to blush.

Painting the entire model white is recommended for a good color base, particularly when white is part of the color scheme. Color coats can be sanded with 360 Tri-M-Ite or 400 or finer wet paper. When using masking tape for trimming, seal the edge with a coat of clear dope to prevent the color dope from bleeding under the edge. Don't leave the masking tape on any longer than necessary. The longer it is on, the harder it sticks.

Complete the job with several sprayed coats of clear over the color scheme. This seals the colors and adds gloss. For best results, it is not a good idea to try to mix different brands of paint. Use SIG products from the start.


A CURE FOR FUSELAGE WARPING
You may have noticed when a piece of balsa is doped on one side and not the other, it will curl. The same thing can happen on the fuselage sides, under the wing opening, particularly when you put on a number of coats. (The rest of the fuselage will not show this effect to any extent because it is four sided and cannot distort.) The effect isn't noticable until after full cure of the dope and aging, which may take several months. To prevent this from happening, give the inside fuselage a coat of dope every time you give the outside a coat. This has an added advantage in making the cabin area fuel proof. In addition, when the hardwood servo mounts are installed, have them a little over-long so that the cabin sides are bulged slightly outward.


Finishing The Plastic

The plastic parts should be sanded to remove the gloss before they are painted. Don't use coarse sandpaper, which can cut deep scratches. These scratches may open up during doping (which softens the plastic) and become more noticeable. Instead use something like 220 3-M Tri-M-Ite no load silicon paper to start and polish down with 360 Tri-M-Ite or 400 wet paper before color doping.

The plastic cowling and wheel covers may be painted with Sig Supercoat Dope. Care should be used not to apply heavy, wet coats of dope. Put on light coats and allow them to dry thoroughly before applying a second coat. A spray gun is a good method of getting a good finish with a minimum amount of dope. Be especially careful with spray cans not to wet the plastic too much. Spray several light dusting coats with adequate drying time allowed. Plastic may also be painted with Sig Plastinamel, Sig Skybrite, K&B Super Poxy, Hobbypoxy or DuPont Dulux Enamel.

CANOPY: We recommend Sig Plastinamel or Sig Skybrite for painting the framing outlines on the canopy. Dope is very difficult to use on canopy plastic because of its warping action. Epoxy paint can be used, but it does not stick on the plastic quite as well as Plastinamel or Skybrite. Sanding the gloss off the plastic will help adhesion. Other enamels and plastic paints can be used, but test in advance on scrap. Glue the canopy on right after the paint is dry.

Decals

Decals are not furnished in the kit. See Sig catalog for special Kougar decals. The water-slide type will not adhere well to plastic film covering. For plastic-film covered Kougars, get Stik-Tite pressure sensitive decals. Stik-Tites can be used on any surface but are slightly thicker than water-slide decals

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Stik-Tite Water-Slide
Cut out the decals with a pair of sharp scissors. Leave 1/32" to 1/16" of clear edge around the decal. Round corners when cutting. Wet the surface on which the decal will be placed with soapy water (dishwater detergent). Place the decal on the model and squeegee the water from underneath with a balsa paddle. Allow to dry. This procedure will prevent air from being trapped underneath as is possible when the decals are applied dry. Dip the decals in water for a few seconds, remove and allow the moisture to soak into the backing to completely loosen the glue. Don't slide the decal off too soon, it may tear. Slide about 1/4" of decal at the bottom over the edge of the backing and align on the surface. Hold decal and carefully slide away the backing from underneath. Use a small paddle of 1/8" sheet balsa about 3/8" wide as a squeegee to remove excess water from under the decal. Hold down one edge with a similar paddle while squeegeeing to prevent the decal from being moved. Allow plenty of time for the glue under the decal to dry before wiping away the excess glue remaining on the surface of the model with a damp cloth. The decals are fuel-resistant with most fuels but will dissolve in dope or cement. Do not try to dope over decals. Some types of clear fuel proofer may be used over decals to increase durability but test them before applying. Leave about 1/16" of clear top coat around the decal stars when cutting them out of the sheet. Round corners to prevent tearing.

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Assemble the tank hardware as shown in the photo. Two vent pipes are used when your engine is equipped with a pressure tap. Run a line from one to the muffler tap. Put a piece of tubing on the other, running outside the cowl for filling. Pump fuel into this until it overflows into the muffler line. Then plug the filling hole with a 4-40 bolt. If pressure is not used, install only one vent. Fill by removing needle valve line, pumping into it until fuel runs out the vent. Bring it out the bottom of the cowl so raw fuel can't spray on the canopy. You can also use pressure on a single vent tank by filling through the needle valve line and letting the line to the muffler top be the overflow vent. See "TIPS ON TANKS" for more information.


CUTTING HOLES IN THE COWL


These pictures show other cowlings but the same principles apply to the Kougar cowl.

Drill a series of holes, about 1/8" nearly touching each other. Cut through the wall remaining with a knife. A slit through the back behind the motor will aid removal. Cut the hole for the head with the carburetor off of the motor so it will be out of the way and then enlarge as required to pass the carb, needle valve, etc.

The best way to open up the hole is to go around the edges with an "applepeeling" motion, paring off a small amount of plastic with each stroke.

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NOSE GEAR

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  1. The nose gear is held in the nylon bearing by the steering arm. Angle the arm forward so that when the servo pulls it back for a left turn, the arm will clear the face of the firewall.
  2. A flexible steel cable pushrod with nylon outer tubing (not furnished) is recommended for the hookup of the nose gear, such as the SIGSH559 Flexible Cable Pushrod. Run the nylon outer tubing through the firewall at the right spot to connect the inner cable to the nylon steering arm. Epoxy around the tubing at the firewall so that no oil will leak into the fuselage.
Clevises
Clevises supplied in the kit may be metal or plastic. If the pins fit too tightly in the nylon horns, open up the hole with a No. 51 drill.

Servo Hook-Ups

Having the proper connector makes servo installation much easier. We show here a variety of ways to attach push rods to servos.


The Rocket City 07 Pushrod Retainer works okay for hooking the wooden push rods to the servo unless the movement or pushrod angle chosen makes it bump into the center post of the servo at the extreme end of the movement. (This can be fixed by changing the angle of approach to the servo or using a longer arm to bring the retainer out farther away from the center post of the servo.) This retainer is very easy to attach and detach.

Du Bro Ball Links, which come in several different types, threaded, bolt-on, rivet, etc., gets the push rod action up above the control arm so the pushrod can approach from a variety of angles without any chance of interfering with the servo center post. It is good for cable pushrods. A fine adjustment can be made by screwing the end in or out.

The SIGSH736 pushrod connector is handy for cable end attachment, as on the nosewheel steering arm, but can also be used on servos as shown. They are easily adjustable by loosening the screw and sliding the cable.

The SIGSH184 or Goldberg Snap'R Keeper can be installed on a wire push rod after it is bent, due to the design of the body of the fitting.

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You should decide on which type of fittings you will use in the case of the cable pushrods and have them on hand during fitting construction because the type chosen will affect the location of the pushrod exit holes through the firewall, etc. The balsa pushrods to the rudder and elevator are not limited as to location and can be adapted to any of the types of connectors shown without preliminary planning of exact position.

Some of the variety of detachable pushrod retainers for securing the push rod wires to the servo that are available are shown here. Or you can make a "Z" bend in the end of the wires to go into the servo. When a "Z" bend is used, the pushrod must be put onto the servo outside of the fuselage and then threaded through the fuselage, which is more difficult to manage than the pushrod alone, as is the case when a retainer fitting is used.
5/16" square balsa sticks are provided to make the fuselage pushrods that run to the elevator and rudder. Bind the fittings to each end with heavy thread and epoxy glue. Use threaded rods with HC links at the tail end of the pushrods so that trimming adjustments can be quickly made. Straight pieces of 1/16" diameter wire are provided for the other end of the pushrods to allow hookup with the servo arm.

PREPARING CABLE PUSHRODS
To keep ends of cable from unraveling during handling, tin the end with solder. Use a non-corrosive paste flux (shown here is Kester, available at hardware stores) and rosin core solder. Have a hot iron and flow the solder completely through the cable.

Grind or file the end smooth. Bring it to a point so that it will easily insert into the pushrod fittings.
After the proper length is arrived at, sweat solder the area to be cut so that it will not fray and unravel while being cut. It can be cut with a good pair of side-cutting pliers, filed in two, ground through on the edge of a grinding tool, or cut with a silicon cutting wheel on a motor tool.

RADIO EQUIPMENT INSTALLATION

The most convenient method of installing servos is on the plastic mounts which most radio equipment makers offer with their outfits or as an accessory. These are screwed to hardwood mounting rails for fuselage servos or to hardwood blocks for mounting in the wings. Instructions for the use of these mounts are included with them.

A flexible cable pushrod with nylon outer tubing (not furnished) is recommended for hookup of the throttle to the motor control servo.

A variety of quickly detachable pushrod retainers are available from Sig Catalog for hooking the pushrods to the servos. SIGSH184 pushrod retainers are recommended, or a solder clevis (SIGSH527) may be used.

Servos, for which plastic mounts are not available can be screwed directly to the two 3/8" square hardwood rails placed across the cabin, three abreast, as shown in the accompanying drawing. With rubber grommets installed in the servo mounting holes, mark the spots for drilling the pilot holes for screws. Space the servos at least 1/8" apart and do not have then contacting the hardwood mounting rails except on the grommets. Using a washer on the wood screws, mount the servos to the rails. Do not tighten the screws down against the grommets since this will cause vibration to be transferred to the servos. The washer should just rest against the grommet without compressing.

The receiver battery pack should be wrapped in foam rubber sheet, held on with rubber bands. It is a good idea to put the package in a small plastic bag, taped shut around the battery cable to protect the battery from leakage.

The receiver should be similarly wrapped up in foam rubber to protect it from engine vibration. Cover it with a plastic bag also. Stow this package just in front of the servos. Make certain that the receiver will stay in place.

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Radio installation in one of the prototype Kougars A UM-3 plastic mount on the 3/8" sq. crosspieces holds three EK-MM servos. The receiver is wrapped in a foam rubber package and stowed just ahead of the servos.

Some RC outfits have one or more reverse direction servos which are handy when it is found more convenient in a particular installation to have a pushrod hook to the servo on the opposite side.


In this installation, using Logictrol SM servos, the battery and receiver have been semi-permanently installed. WIth scrap balsa crosspieces holding the foam rubber wrapped packages in place. The motor and nose wheel pushrods are tacked to the crosspiece over the receiver with 5-minute epoxy. If necessary to remove the equipment, break out the battery retaining cross-piece and pull out the battery and the receiver, leaving the receiver retaining strip in place. (Some Kougars may need the battery in the nose under the tank for proper balance.)

Control Movemants

Various brands of servos can give different control movement direction and amounts of travel. For this reason, follow the measurements below when setting the Kougar up for flight rather than any particular horn hole drawn in this book or visible in a Kougar picture. Shift the RC link to whatever horn hole will produce the amount of movement shown in the drawings below. Measurements are made at the trailing edge of the control surface.

The control measurements shown should give full aerobatic capability. Test flights may indicate a need for more or less movement, depending on individual model differences, C.G. location, your personal preferences, etc. (Flight Tests may determine that the neutral point should vary slightly from level but for purposes of illustration the neutral point is shown level.)

For training purposes, do not carry excessive elevator movement. Use only enough to properly perform a nice sized loop at full travel. Over control with excessive movement can get a novice in trouble. After you are more expert, additional movement can be used, if desired, for quick snaps and other violent maneuvers.

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WHY MODELS MUST BE INDIVIDUALLY BALANCED
It is impossible to produce a kit that will automatically have the correct Center of Gravity (C.G.) position. Balsa wood varies in weight and it is easily possible for wood in the tail to be an ounce or more heavier or lighter than average. One ounce of extra weight in the tail has to be countered by about 3 ounces in the nose. Don't pile a lot of fillercoat or finish, use excess glue or make large fillets on the tail surfaces. The motor you choose, whether or not a muffler is fitted, the size and placement of your radio equipment, etc. all affect the balance. If you use an unusually heavy motor or muffler you may have to carry the battery in the radio compartment instead of the nose or even weight the tail. Don't consider that whatever C.G. the model builds out to as "good enough". Check carefully and make whatever adjustments that are required. With the C.G. properly located, a Sig design should fly with only minor trim changes required.


Balancing

The recommended Center of Gravity locations are:
  • Test Fly with the balance point located anywhere between the leading edge at the wing tip and 1/2" back from the leading edge at the wing tip.
  • Sport Fly at 1/2" back from the Leading Edge at the wing tip.
  • Aerobatics - If your model will spin in both directions at 1/2" it need not be moved back any further. Some models need the balance point at 3/4" back for full response.
Flying with the balance point any farther back than 1" from the tip is not recommended unless you are an expert flier, with a purpose for doing so.

For the first test flight, balance the Kougar by suspending it on the finger tips placed on the bottom of the wing on the first mark. Balance with an empty fuel tank, but with all other equipment installed and the model completely finished and painted. Add lead to the nose, if necessary, to get the model to hang level. Be sure and fasten the weight securely. Do not attempt flight tail heavy.

The "Test Flying" position is on the nose heavy side. When slightly nose heavy, the model is more stable and less likely to stall or snap roll from over-elevating. It also cuts down reaction of the model to control movements and this is good during test and practice flights, to help prevent overcontrolling. After the model has been test flown and initial trimming accomplished you may want a little quicker response. Move the balance back slowly and check results in the air.

Some aerobatic capability is sacrificed with the forward C.G. positions, so for making deliberate snap rolls and spins a position farther back may be required. Move the C.G. back slowly and check results and control response in the air at a good altitude. Don't move the C.G. back any farther than necessary.

BALANCE IS PART OF THE TRIMMING PROCESS
The balance point we arrived at for this design is a good place to start when trimming out the model for top performance. However, it should not be considered the final and irrevocable location. Individual models built from the same kit are slightly different from each other. The incidence may be changed a bit, a small or large engine selected, the total weight varies - even the skill of the pilot has bearing on just what should be the exact C.G. point. For example, when slightly nose heavy, the model is more stable and less likely to stall or snap roll from over-elevating. This also cuts down the reaction of the model to control movements which is good during test and practice flights to help prevent overcontrolling. But later, if extra sensitivity and quick reactions are desired for aerobatic performance, a position farther back may be desirable. So try different positions, but make the changes gradually, checking results and the effect of the change control responses and the performance of the model in the air at a good altitude.

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FLYING

IMPORTANT: The Kougar is not a basic trainer. If you have no previous RC flying experience you cannot successfully fly a fast and responsive design like the Kougar, particularly on test flights. It is suggested that you not attempt flying without the assistance of a modeler with experience. Contact your local model club or ask your hobby dealer for the names of good fliers in your vicinity and a suitable location for flying.

Many hours of work are involved in the construction of a model and it can all be lost in a moment of beginner's indecision. A skilled flier can help you get past the first critical test and trimming flights without damage to the model and give instruction in proper control.

Be certain to carefully range check your radio equipment and see how it operates with the engine running before attempting test flights.

A lot of problems can be avoided if the engine has been well broken-in and the idle adjustment perfected on a test block or in another airplane before installation in the model.


Takeoffs with the Kougar from grass fields are easily made if the grass is not too long or the ground too rough. Generally a lot of elevator application is required for liftoff.

Be prepared to relax control pressure partially after becoming airborne so the climbout will not be too steep. On surfaced or smooth dirt runways less application of elevator will be needed.

If a good, smooth take-off surface is not available, the model can be hand launched by the pilot's assistant. (Do not attempt to hand launch by yourself --- instant action on the transmitter may be required.) Holding the front part of the fuselage with the left hand and under the tail with the right, run into the wind at a fast trot and thrust the model forward with the nose slightly up in a spear throwing motion. It is not necessary to achieve a lot of velocity in the launch-it is more important that it be released smoothly and with the wings level. The model may dip slightly and then should begin climbing at a slight angle. If it does not begin to climb after about fifty feet of flight, apply a small amount of up to lift the nose. Use hand launching only as a last resort.

Use the ailerons to keep the wings level and headed straight into the wind until about seventy-five feet of altitude is obtained. Keep first turns gentle and not steeply banked. Stay up wind of the transmitter. Use trim levers on your radio equipment where necessary to obtain straight and level flight with the control sticks in neutral position but don't attempt to make these adjustments until the model is at a good altitude. Throttle back at altitude to find out the model characteristics in a gliding condition so that some indication is seen of what to expect during the landing approach. It is a good idea to make several practice landing approaches at a good altitude to get the feel of the model for this approaching critical maneuver. Make your final and complete landing approach while your engine still has plenty of fuel remaining so that the engine is not liable to stop before completion of the flight. This will allow application of power if the approach is undershot. Notice the percentage of missed landings at an R/C flying field. Those undershot greatly outnumber those missed by overshooting. So, if an approach that looks a little high is maintained, chances are good that a spotlanding can be made.
After each test flight, readjust the RC clevis links on the pushrods so that the trim levers on the transmitter can be returned to a neutral position. It will take several flights before exact trim is established on all axis of flight.

Print, cut out and join the following pages together in order for the plans.

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© Copyright SIG Mfg. Co., Inc.

SIG MFG. CO., INC.

Montezuma, Iowa 50171-0520
LIMIT OF LIABILITY:
In use of our products, Sig Mfg. Co.'s only obligation shall be to replace such quantity of the product proven to be defective. User shall determine the suitability of the product for his or her intended use and shall assume all risk and liability in connection therewith.