CITABRIA RC30 RADIO INSTALLATION
It is generally easiest to mount all your radio equipment and pushrods in your Citabria before covering and painting. Once the initial installation has been made and all the bugs worked out, you can remove the radio system and then reinstall it when the airplane is finished.
Mounting Servos In The Fuselage
The most convenient method of installing the elevator, rudder and throttle servos in the fuselage is on the plastic trays supplied by the manufacturer with most radio systems. These plastic trays are screwed to hardwood mounting rails that are epoxied across the inside of the fuselage.
|We recommend that the hardwood mounting rails be made of at least 3/8" sq. or 3/8"x1/2" basswood, pine or spruce. Do not make the rails out of balsa! Glue scrap pieces of balsa to the fuselage sides around the ends of the servo rails so that they can never come loose in flight. Further instructions on the use of servo trays can usually be found in the instructions supplied with the radio system.|
The fore and aft location of the servos is generally not critical for balancing purposes. The servos in the photo model were towards the rear of the cabin for easy access even with a pilot installed. The servos were also mounted fairly low in the fuselage so that they wouldn't show through the windows.
Elevator And Rudder Hookup
Attach a small nylon control horn to the rudder and a medium nylon control horn to the elevator using #2x1/2" sheet metal screws. Mount the rudder control horn on the right side of the rudder and the elevator control horn on the bottom of the left elevator, as shown on the plans.
The type of pushrods that you use to actuate the elevator and rudder is left to your preference. Although the photo model uses balsa pushrods, it may actually be easier to install flexible nylon tubing pushrods, especially to the elevator. Sig 30" Nylon Tubing Pushrods (SH-568, see Sig Catalog) can be used. The outer tubing of the pushrods must be supported every four to six inches and permanently installed in the Citabria before it is covered.
The pushrods can also be made of balsa, as shown here. The 1/4" sq. balsa sticks are not provided in the kit, but the 2-56x10" threaded rod and nylon links are. Make the control surface ends of the pushrods first. Cut and bend the threaded rods as necessary to route them clear of the fuselage. In general, the fewer bends the better, but the elevator position requires the threaded rod to take a rather complicated route. Drill a 1/16" dia. hole 2" from one end of the 1/4" sq. balsa pushrod stick. Push the 90 deg. end of the wire into the hole, wrap the wire to the stick with the thread, and coat the winding with glue. Let dry.
Carefully try to determine the spot on the side of the fuselage where the pushrod will exit and line up with the control horn and servo. Cut a 1/8"x3/4" slot at this spot. Feed the pushrod through the fuselage, sticking the threaded rod through the slot. Screw a self-threading nylon RC link onto the end of the pushrod and hook it up to the control horn.
Hold the control surface in its natural position and cut off the servo end of the balsa pushrod stick about 2" short of reaching the servo's output arm. Attach a 6" long piece of 1/16" dia. music wire to the servo end of the balsa pushrod stick using the same method as the other end. Coat with glue and let dry.
Feed the pushrod back into the fuselage and hook it up to the control horn. Make sure the nylon link is centered on the threads at the tail end so that you will have equal adjustment range either way. Hold the control surface in its neutral position and attach the pushrod to the servo using your choice of servo connector.
It is very important that you make sure that both of your pushrods operate smoothly (without excess slop) and that they don't interfere with each other. When the fuselage is covered, the pushrod exit slots will have to be recut in the fabric. The loose covering material around the slot should be covered with reinforcements cut from the this plastic piece included in the kit. Use the pattern shown for your slot reinforcements.
Receiver And Battery Installation
Wrap the receiver and battery pack separately in foam rubber (such as Sig RF-240), held on with rubber bands or tape, to protect them from engine vibration. The best location in the fuselage for the receiver and battery can't be determined until your model is completely finished. Shifting these components fore and aft can help get the model balanced properly. The photo model has the battery located below the fuel tank and the receiver positioned just behind former F-3B. After determining the best locations, glue temporary pieces of scrap balsa between the fuselage sides to hold the receiver and battery in place so they will not move around in flight.
The receiver antenna can be run out of the bottom of the fuselage and tapped at the aft end. This will expose the antenna without making it too conspicuous. Most servo trays make a provision for the switch to be mounted to it. Run a small piece of wire from the switch to the outside of the model so that you can turn it on and off. Also be certain the charging jack is easily accessable inside the fuselage.
Bend two 2-56x10" threaded rods to match the aileron pushrods shown on the plans. Slip the pushrods onto the aileron bellcranks, thread two nylon RC links onto the ends of the pushrods and attach the links to the aileron control horns. Adjust the nylon links until both ailerons line up perfectly with the wing and check for smooth operation.
Cut the servo access hole in the bottom of the wing center section to expose the aileron pushrod. The aileron servo is mounted on a plastic tray designed to hold just one servo. The tray in turn is screwed to a plywood plate which is glued to the upper center section sheeting. The plywood plate, in this case 3/16" thick, also serves to raise the servo to the perfect height for the small spur wire.
|Make a spur wire from 1/16" dia. music wire to connect the aileron pushrod to the aileron servo output arm. Wrap the spur wire in place on the pushrod
splice with copper wire. Carefully position the spur wire so that the ailerons are in neutral when hooked up to the aileron servo. Solder the spur wire firmly.|
Use a flexible cable pushrod, such as the Sig Flexible Cable Pushrod (SH-559), to connect your throttle servo to the control arm on the engine's carburetor. A typical installation is shown above.
|The throttle on the 4-stroke engine used in the photo model is set-up a little differently. The carburetor is located on the rear of the engine which doesn't leave enough room for the threaded coupler and
nylon link. Instead of using those parts, a Du-Bro Ball Link Socket was attached to the cable by wrapping it in place with copper wire and coating the windings with CA glue. The ball Link Socket then attaches
to a Bolt-On Ball Link which is installed on the carburetor control arm.|
The flexible cabel pushrod should be supported at the servo end so that it is aimed directly at the output arm on the throttle servo. Cut a support block from scrap balsa and glue it firmly in place against the fuselage side. Epoxy the nylon outer tubing to the support block. When dry, cut the nylon tube and the cable to the final length needed to accommodate your choice of servo connector and install it into the end of the cable.
Tips On Tanks
An 8 ounce plastic clunk type tank is recommended for use in the Citabria. The plans specify a Sullivan Slant-Oval type fuel tank, but a rectangular or round tank can be substituted with good results. The slant-oval shape allows plenty of room beneath it for batteries, and helps keep the fuel level closer to the center of the carburetor.
The simplest, most trouble free tank set-up to use in the Citabria is normal suction feed with two vents . Assemble the fuel tank hardware as shown in the photo. There are three tubes installed through the rubber stopper - one for fuel feed and two for vents. Both vent tubes should curve upwards inside the tank. The clunk line on the fuel feed tube must swing freely without hitting the back of the tank.
After the model is covered and painted, you can mount the tank permanently. For best results, the tank should be mounted high in the fuselage so that the centerline of the tank is 1/2" to 3/4" below the carburetor centerline. Make scrap balsa supports to position the tank as desired and to hold it in place. Should the need ever arise to remove the tank for servicing, simply break away the balsa supports. You can seal around the holes in the firewall where the fuel lines come through with silcone rubber sealer to prevent oil from leaking inside the fuselage.
Run Sig Heat-Proof Silicon Tubing from the fuel feed line to the carburetor. Two more lengths of tubing run from the vent tubes to the bottom opening in the cowl. To fuel the aircraft, simply pump fuel into either of the vent lines until it runs out the other. Plug one of the vents with a short 4-40 bolt to keep the fuel from siphoning out. It's not necessary to remove the feed line from the carburetor to refuel.
If your engine's muffler is equipped with a pressure tap, you can make use of it to help provide a more reliable fuel feed. To do this, connect one of the vent lines to the pressure tap. The other vent line must still be plugged with a bolt to operate properly. To refuel, remove the vent line from the pressure tap and remove the bolt from the other line, then fill the tank as you normally would. This method is used on the photo model.
|COVERING AND PAINTING|
You have now reached the point where your Citabria will take life and begin to look like its real counterpart. The most realistic finish for the model will require that it be covered with some type of fabric, such as Sig Koverall. An iron-on plastic covering will work, but it won't give the strength of a fabric covering and won't appear very realistic. Whatever type of covering you desire to use, it will not conceal a rough framework. Be sure all surfaces are smooth before proceeding.
The manufacturers directions for applying iron-on coverings are packed with the material. Follow these closely, for different types of material have different iron temperatures and techniques of application. The rest of these instructions describe the use of Sig Koverall.
Koverall is a polyester-base, heat-shrinkable, synthetic fabric much like the covering used on full-scale aircraft such as the Citabria. It is relatively low cost and will add a great deal of strength to the model's framework. It can be applied to the model using dope or Sig Stix-It, a heat activated adhesive.
To apply Koverall with dope, you must first prepare the framework by brushing on two coats of clear dope wherever the covering material will touch. If you plan for the entire finish, use Sig Supercoat (butyrate dope) for the first two coats. If you plan to use enamels or epoxy colors, use Sig Nitrate dope. Lightly sand after each coat to remove any raised grain or fuzz.
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). Lay the Koverall on the wing, pulling out any large wrinkles. Koverall shrinks up considerably under heat. (Don't worry about such things as the packaging fold wrinkles - they will come out easily with the iron.) Brush clear dope around all the edges. This will soak through the fabric and adhere it to the dope already dried into the framework. Allow the dope to dry before trimming off the excess material with a sharp razor blade. Check for any rough edges or places that are not stuck down properly and apply more dope, let dry.
After both sides of the wing are covered, shrink the Koverall evenly with an iron or hot-air gun (read the Koverall package instructions).
The Citabria fuselage is covered using four separate pieces of covering material. The first piece is applied to the bottom and attached to the stringers which run along the bottom of the fuselage sides. The next two pieces are applied to the fuselage sides. These pieces should attach to the bottom stringer (overlapping the first piece of fabric about 1/4") and the upper stringer which runs from the top rear of the cabin to the tail platform. Also attach these side pieces to the entire window frame (cut the material away from the windows later.) The front end of these two side pieces can wrap over the nose planking and join at the middle. The final piece of fabric covers the upper stringers and should overlap the side pieces about 1/4" on each side. Do not shrink the fabric on the fuselage until all of the pieces have been applied and allowed to dry completely.
|Each of the tail surfaces can be covered using two pieces of Koverall, or one piece wrapped around one of the straight edges.|
The directions for applying Koverall with Stix-It are on the can. The basic procedure is to apply Sitx-It around the edges of the framework where you want the covering to attach. Lay the fabric in place and use an iron to activate the Stix-It. Once covered, the fabric is shrunk using the iron or a hot-air gun. Whether using dope or Stix-It to apply the Koverall, the remaining steps are identical.
Once the model is covered give the whole airplane a coat of clear dope. Thin the dope until it brushes on easily and flows out smooth. Brush the dope on sparingly over the open framework areas. If too much is applied, the excess dope may rub off the brush, run completely through the covering and puddle against the covering surface on the other side. When these puddles dry, the large amounts of dope solids in them cause more shrinkage than in the rest of the covering and a scarred area may result. The second coat of clear dope will seal most of the pores of the Koverall and from then on running through will not be a problem. Sand the model VERY LIGHTLY with FINE sandpaper after the second coat is dry. Then give it a third coat of clear dope and when dry, sand again.
Your Citabria is now ready to be finished with its colored paint scheme. It is generally better to apply light colors first, followed by darker trim colors. Use "low-tack" drafting tape to mask off the paint scheme. If you have used Sig Supercoat dope throughout, a final coat of clear over the color paint will add a nice gloss to the finish. Do not try to mix different brands of paint. Use Sig products from the start and follow the instructions that come with them carefully for best results.
Painting The ABS Plastic Parts
The plastic parts should be sanded to remove the gloss before they are painted. Use only 220-grit or finer sandpaper.
We recommend that the plastic parts be painted with Sig Supercoat Dope or Sig Skybrite paint for best results. Sig Plastinamel, Hobbypoxy, K&B Superpoxy, and Dulux (automotive) enamel have also been proven compatible with ABS plastic and can be used if desired.
|Skybrite primer or K&B primer may also be used for a smooth undercoat. Do not use other paints, dopes or finishes without first testing to make certain
it is compatible with the plastic.|
CAUTION: Do not try to cover the ABS plastic parts with Monokote or other iron-on types of covering material. The heat may melt and distort the plastic.
Installing The Windshield And Side Windows
Cut the windshield from the 8"x12" clear plastic sheet using the pattern below (joining the two sides together). Cyanoacrylate adhesive works best for gluing the windshield to the painted fuselage. (Don't use CA "accelerator" or "sticker" - these could permanently fog your plastic windshield.) A little patience during this step will usually be rewarded with a neat-looking installation.
|Tape the windshield in place as well as possible for a trial fit, then trim as necessary for a perfect fit. With the winshield taped down in it final position, tack glue it in several places along it's edges. It's best to start gluing near the middle of the nose top and at the top of P-1. When satisfied with the fit, glue all of the edges permanently, removing the tape as you go.|
Two 4"x14" pieces of clear plastic are provided for the side windows. One piece is to cover all the window area on one side of the airplane with no seams. Lay the plastic sheets on the fuselage and mark them about 1/8" larger than the outline of the windows. Cut them out and glue them to the outside of the model.
Some modelers enjoy spending many hours providing their models with intricate detailing, while others spend no time at all. The interior of your Citabria can be given as much scale detailing as you wish, however no materials are provided in the kit for this purpose. The following ideas are suggestions only, but will give your airplane a nice appearance without expending too much time and money. Whatever you elect to do for the interior, remember to try and keep weight build-up at a minimum.
|Paint the interior - When you are brushing a couple of coats of clear dope onto the fuselage frame, why not add a couple to the interior, especially around the window frames? Some flat black or grey on the
inside will look better than exposed balsa and plywood.|
Instrument panel - Model-sized instruments are available from several manufacturers and can add a touch of class even if you don't copy an existing panel in a real Citabria.
Pilots - Several manufacturers also produce dummy pilots in the 1/6 scale of your Citabria. You can use just a pilot or a pilot and passenger mounted on a removable base. The base will also help hide your radio equipment which can be installed lower in the fuselage.
Be certain to range check your radio equipment according to the manufacturer's instructions before attempting test flights. A lot of problems can also be avoided if your engine has been well broken in and the idle adjustment perfected on a test block or in another airplane before installation in the new model.
Various brands of servos can give different amounts of control surface travel. By moving your pushrod linkages into a different hole of the control horn and/or into different hole of the servo arm, you can change the total amount of control surface travel you'll get when the Tx stick is moved to full throw position. Adjust your pushrod linkages to produce the amounts of movement listed below.
Measurements are made at the trailing edge of the control surface.
The control measurements listed above should give full aerobatic capability if your Citabria is properly balanced. Test flights may indicate a need for slightly more or less movement, depending on individual model performance and personal preference.
Before flying, you should also adjust all your pushrod linkages so the control surfaces are in neutral position when the Tx sticks and trim levers are centered in neutral. After the first flight, readjust the linkages if necessary so that the trim levers can be returned to neutral position. It may take several flights before exact trim is established on all the flight controls.
Balance your model at the point indicated on the plan. If it balances further back, add weight to the nose as necessary. Trying to fly with the C.G. too far back is much more dangerous than the slight increase in wing loading caused by adding lead to the nose. Balance with an empty fuel tank.
A model, engine or radio that is not prepared and working properly on the ground before takeoff will not improve in the air -
IT WILL GET WORSE!
There is no point in attempting to fly until everything is 100% correct.
The Citabria is a fun and easy aircraft to fly, but it is not a basic trainer. If you have no previous RC flying experience we suggest that you not attempt to fly your Citabria without the assistance of an experienced pilot. Contact your local 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 be lost in a moment of beginner's indecision. A skilled flier can help you get past the first critical test flights without damage to the model.
|For the first flights, line the Citabria up in the middle of the runway for takeoff. You may find it more comfortable to stand directly behind the model so that you can easily see and correct any changes in heading
during the takeoff roll. To avoid a nose-over, you should hold about half of your available "up" elevator while you advance the throttle. It is important to slowly return the elevator to neutral during the
takeoff roll. Be ready to apply a small amount of right rudder because the Citabria will generally tend to drift to the left due to torque. When you reach flying speed, pull back slightly on the elevator stick for a
The most common mistake made during initial test flights, particularly with tail draggers, is overcontrolling with the rudder during the takeoff roll. Remember to make gentle control inputs and you will do just fine. If the model does begin going from one side of the runway to the other (as a result of overcontrolling), quickly pull the throttle to full low, and taxi back for a fresh start. Never try to hurry your Citabria off the ground by pulling full up elevator just because it isn't going straight! This could lead to a premature snap roll (due to low airspeed) which would damage your model much more severely than anything that could happen on the ground. Make several practice takeoff runs without lifting off to study the airplane's ground handling characteristics.
In the air, you will find the Citabria to be very smooth and stable. It will perform very realistic maneuvers with ease. After the model has been trimmed and you are more familiar with it's flying qualities, you may want to experiment with slight changes in control surface travel until the Citabria flies and reacts just the way you want it to.
Advanced pilots who are striving for maximum realism and smoothness should "coordinate" their turns by adding a small amount of rudder at the same time and in the same direction, as the aileron. Many of the newer radio systems offer a "coupling" feature which will automatically deflect the rudder slightly when you use the aileron stick.
Shifting the balance point forward or aft will also affect the aircraft's handling characteristics both on the ground and in the air. We recommend that you shift the balance point no more than 1/8" at a time and that you don't shift the balance point more than a total of 1/2" forward or aft of the position shown on the plans. Moving the balance point forward will increase the model's stability, and slow down snap and spin maneuvers. On the ground, a forward balance point will decrease any tendency to veer left or right, but will increase the possibility of a nose-over. Shifting the balance point aft will make the model much more sensitive to control inputs, both on the ground and in the air. If carried too far, the model will become completely unstable and uncontrollable. If these ideas have made the Citabria sound as though it is difficult to fly, it really isn't. These are basic laws of aircraft design and aerodynamics that apply to ANY AIRCRAFT, model or full scale, not just the Citabria. Experimenting with different balance points should only be attempted by experienced pilots. The balance point shown on the plans gives the Citabria a nice blend of stability and maneuverability, and is the balance point we use on our prototypes.
When the time comes to land your Citabria, remember to keep your control inputs smooth and gentle to avoid overcontrolling. When you are certain that the model will make it to the runway (even if the engine quits), bring the throttle to full low and concentrate on keeping the wings level during final approach. Slow the model down during the entire approach by slowly feeding in up elevator. Just before the model touches, flare the landing by carefully feeding in more up elevator. Hold the model just inches off the ground until your elevator stick is pulled all the way back. The Citabria should settle down to a perfect "three point" landing with a short rollout. Taxi back slowly and graciously accept all the praise offered by any onlookers. The hoopla should be overwhelming!
Other Paint Schemes
Several different paint schemes have been used on Citabrias and Decathlons over the years. If you wish to use a paint scheme other than the one shown here, a trip to your local airport could very well turn up a Citabria that you can duplicate. Magazines are another good source for different paint schemes. Her is a list of magazines that may prove useful
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