CLIPPED WING CUB RC47 FINISHING AND FLYING

19.

Covering And Painting The Framework

The completed Cub framework can be covered with Sig Koverall, Sig Silk or an iron-on type of covering material (either plastic or fabric). Whatever type of covering you desire to use, it will not conceal a rough framework. Be sure all surfaces are smooth before proceeding!

The manufacturer's 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, which is a polyester based synthetic fabric ideally suited to quarter-scale models due to its low cost, workability, and toughness. Silk is applied in the same way, but it costs much more per yard. Koverall is highly recommended for the Cub - all of our prototype models were covered with it.

Brush an unthinned 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.

Hints On Covering The Fin Fillet
On the full-size Piper Cubs, the fuselage and fin are covered with one continuous piece of fabric. It bridges from the top stringers of the fuselage sides up to the fin bottom rib, producing a beautiful fillet.

The construction of this model Cub duplicates this feature. Your covering material should bridge from the sheet balsa Tail Fairings up to the fin bottom rib. This may at first appear to be a difficult job to do, but it's much easier than you'd think.
If you're using a dope-on type covering, proceed as follows:
  1. Cut a piece of material that will cover the entire left side of the fin and left side of the fuselage top (all the way forward to the wing T. E. Crosspiece).
  2. Dope the edges of the covering down along the fuse 3/16" x 3/8" Top Stringer, the 1/4" sq. Corner Stringer, and the T.E. Crosspiece. Pull out any large wrinkles or sags in the fabric.
  3. Straighten out the rear end of the covering and adhere the bottom of it to the Tail Fairing. Work the material smooth and dope it down to R4 and the fin bottom rib. Use plenty of pins to hold securely until dry.
  4. Apply three extra coats of clear dope along the fabric stuck to the fin bottom rib. Let dry between coats.
  5. Finish sticking down the remainder of the covering piece ot the top of the fin.
  6. Now repeat the steps to cover the right side of the fin and the fuselage top in the same manner.
When dry, resume following the rest of the written instructions for doped-on coverings. Be careful when applying the pre-color clear dope coats over the entire model that you don't soften the bond of the fabric to the bottom rib and let it pop loose. It's best not to put any dope of the fin bottom rib while painting the surrounding fin and fillet areas.

If you're using an iron-on type of covering, apply it basically the same as described above with one exception. Lap and adhere the fillet covering piece over onto the top side of the fin bottom rib and cut it off there. Then, after shrinking the fillet area tight, cover the top part of the fin with a separate piece. Overlap it slightly onto the fillet covering. If you try to do the job in one piece, the heat of shrinking the entire area will always pop the covering loose from the fin rib.

The bottom of the wing is a good place to start covering. Cut a piece of Koverall about 1/2" larger all around than half of the wing, with the grain running lengthwise. (The grain of woven materials run parallel to the finished bias edge.) Dip the piece of covering in water, let the excess water run off, and then lay it on the wing. Go around the edges, pulling out the wrinkles and stretching the material smooth. Brush clear dope around the edges. This will soak through the fabric and adhere it to the dope already dried into the framework. Let dry before trimming off the excess material with a sharp razor blade. Check for any rough areas or places that are not stuck down properly and apply more dope.
Use the same process to cover the top of the wing, the fuselage, and the tail surfaces. Be sure to read "Hints on Covering the Fin Fillet".

After all covering is done, allow the water to dry out of the fabric and wood. If the Koverall is slack or baggy in any places, use a hot air gun or hair dryer to shrink it tight (read Koverall package instructions).
Next give the entire model a coat of Lite-Coat clear dope. Thin the dope until it brushes on easily and flows out smoothly. 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.

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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 results. So apply dope very lightly the first time over. The second coat will seal most of the pores of the Koverall, and from that point running through will not be a serious problem.

You can put anywhere from 3 to 5 total coats of clear dope on the Koverall before going to color. It depends somewhat upon how heavy a coat you are putting on. Keep the dope thinned out enough to flow on smoothly. Sand well between the later coats of dope with 220 grit Tri-MIte paper. Don't bear down on the edges of the balsa structure or the fabric may be cut. Use your own judgement about when you've put on enough coats. The goal is a completely smooth and even base for the color paint. Keep in mind that weight can build up fast in finishing and restraint must be used in application. Don't try to completely fill the grain of the fabric like you would on a smaller model. The weave will not be very noticeable as long as the edges are smooth - it may even look more realistic. Sanding sealer or primer is not necessary or advisable.

Best results can usually be obtained by spraying on the color finish coats. It is also much faster than brushing would be on this large a model. Reduce the dope for spraying fifty-fifty with Sig Supercoat Thinner. Two coats of your base color should give good coverage if the surface preparation was sufficient. If any light sanding between base color coats is needed, use 360 Tri-M-Ite or 400 or finer wet paper.

When the base color has dried, mask off the edges of the color trim areas with "drafting tape" (3M Scotch brand is available at most office and art supply stores). Completely cover with paper and tape all areas that should remain base color. Brush or spray the edges of the tape with clear dope. This seals the tape, preventing leakage of the trim color underneath the tape. Spray on two coats of trim paint. When dry, carefully remove the tape.

Complete the job by spraying a coat of Lite-Coat clear dope over the entire color scheme to protect the colors from scuffing and to give the entire model a uniform gloss.

For best results, it is not a good idea to try to mix different brands of paint. Use SIG products from the start.

Bottom View Color Scheme

20.

Sanding And Painting The Plastic Parts

CAUTION: Do not try to cover any of the plastic parts with Monokote, Coverite, or other iron-on types of covering material. The heat can damage the plastic parts.

The cowling, dummy engine, and bungee covers are molded out of ABS plastic. We recommend that they be painted with Sig Supercoat Dope for a good color match to the rest of the doped model. Hobbypoxy, K & B Superpoxy, and Dulux Enamel have also been proven compatible with the plastic. Do not use other paints, dopes, or finishes without first testing on scrap plastic to make certain that they are compatible.

In preparation for painting, the plastic parts should be sanded to remove as much of the surface gloss on them as possible. Do not use coarse sandpaper which will cut deeply into the plastic. Deep scratches will often open up wider during painting. Use 220 grit or finer 3M Tri-M-Ite Fre-Cut Finishing Paper (see Sig Catalog) or its equivalent.

Color paint can be put directly on the sanded plastic. Primer type coats are not necessary if a thorough sanding job was done with fine paper. Brush or spray the color paint onto the plastic parts. Do not apply heavy, wet coats which can cause an "orange peel" effect. Put on light coats and allow them to dry before applying a second coat.


The "stand way off scale" detailing of the dummy engines on our prototype models was done by painting with 3 basic colors:
Silver for the cylinder heads and the outside of the top shrouds.
Black for the inside of the top shrouds, the cylinder fins, and for any recessed or shadowy areas.
Steel for the exhaust pipes and the cylinders. This isn't a standard color, you'll have to mix your own by slowly adding black paint to silver until you get the shade you want. It shouldn't be too light colored, but must provide adaquate contrast with the black painted area.
The silver painted areas should be glossy when dry. The black and steel areas should be flat, non-glossy.

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21. Painting The Landing Gear And Wing Struts

The completed landing gear and wing struts should be painted with epoxy type paint (Hobbypoxy or K & B Superpoxy) because of the large amounts of metal to be painted. Dopes do not stick well to metal, but epoxy paint does.

Brush or spray a coat of epoxy primer on the entire part and sand smooth when dry. Repeat applications of primer and thorough sanding until the surface of the wooden and fiberglassed areas are smooth.

Spray on two coats of color, letting dry between coats.

22.

Self-Adhesive Decals

Cut out the decal you wish to apply with a sharp scissors, modeling knife, or single-edge razor blade. Trim close to the image, leaving about 1/32" to 1/16" of clear edge around the decal. Smaller designs (2 - 3 sq. in. or less) can be put on the model by "dry application", whereas larger decals go on easier using the "wet application" instructions.

Instructions for Dry Application

Peel the paper backing sheet completely off the decal, being careful not to let the sticky side double over and adhere to itself. Hold the decal in position just above the surface of the model while you double check to make certain it is exactly where you want it. Don't let the decal contact the surface of the model until you are sure of its location! Once it is stuck down, it can't be moved! Start the actual application by pressing just one edge of the decal into contact with the surface of the model, and then carefully work towards the opposite edge, slowly rubbing the remainder of the decal in place. Be careful not to trap air under the decal. If air is trapped under the surface, puncture the air bubble with a pin and press down.


Instructions for Wet Application

Here's a little trick that allows application of self-adhesive decals to a model without the danger of trapping air bubbles. Start by wetting the surface of the model where the decal will be placed with a generous quantity of soapy water solution (a little dish soap in water, or a commercial cleaner like Sig Blue Magic Model Airplane Cleaner, "409", or "Fantastic" brand cleaners will all work equally well). Peel the paper backing sheet completely off the decal, being careful not to let the sticky side double over and adhere to itself. Place the decal onto the wet surface of the model. The soapy water will keep the decal from actually sticking to the model until you have had time to shift it around into exact alignment. Once you have it in exact position, use a small paddle of scrap sheet balsa to squeegee the excess soapy water out from under the decal. Squeegee repeatedly to get as much of the soapy water out from under the decal as possible. Allow to dry overnight. When completely dry, wash off the soap smears with a clean wet rag.

NOTE: These decals are completely fuel proof and cannot be harmed by any common model -airplane glow fuel containing less than 20% nitromethane. Higher quantities of nitromethane may cause slight deterioration of the decal over extended periods of time.

WARNING: Do not try to paint over these decals. Model cement, butyrate dope, lacquer, epoxy, and enamel paints may dissolve the decals. If you wish to top coat your decals, be sure to test for compatibility on a scrap decal before applying the paint. Frankly, Sig Mfg. Co. does not recommend top coating and will assume no liability for problems you may encounter.

23.

Attaching The Tail Brace Wires

Four 2-56x10" threaded rods are provided for the Brace Wires. Cut two of them off at 8-3/4" long for the bottom brace wires. Leave the other two at 10" long for the top brace wires.

Four standard RC links (2-56 thread inside) and four solder links (unthreaded) are provided for the ends of the Tail Brace Wires. Take each link and cut off the side that has the pin in it. (A Dremel tool with an abrasive cut-off wheel works best.) Enlarge the hole in the remaining half with a #44 drill bit.

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Screw one threaded link and jam nut onto the threaded end of each rod. Solder one of the unthreaded links to the other end of each.

Drill #44 holes through the stab and fin trailing edges at the brace wire attachment points drawn on the plans.

Fit the wires to the model. Bend the ends of the links as needed to make them fit flat against the model surface. Use 2-56x1/2" bolts and hex nuts to fasten the links through the stab and fin. Use #2x3/8" sheet metal screws to hold the bottom of the lower brace wires to the plywood tailwheel mount.

Adjust the threaded links and jam nuts until the wires are snug, but not pulling the tail surfaces out of shape.

Paint the tail brace wires after installation with epoxy paint.




24.

Installing The Windshield And Side Windows

Cut the windshield from the 1-1/12"x17" clear plastic sheet, using the pattern on the plan. Cyanoacrylate adhesives (Hot Stuff, Jet, etc.) work best for gluing the windshield in place on the fuselage. This is a tedious and sometimes frustrating job - but a little patience and thought will usually be rewarded with a good fitting installation.

First pin the windshield in place as well as possible for a trial fit. Readjust where necessary. Then go around the edges and tack glue in several places. It's best to start gluing near the middle of the nose top and at the top of F5. Then work out towards the sides and the Windshield Braces. Don't try to bend the plastic around the Braces, just glue it to the front edge. When satisfied with the fit, glue all the edges permanently. When dry, trim off the excess plastic along the Windshield Braces.

Two 5-1/2"x17" 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 out and glue on the outside surface of the model.

25.

Preflight

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.

Why Models Must Be Individually Balanced

It is impossible to produce a kit that will automatically have the correct balance point. Balsa wood varies in weight and it is easily possible for the wood in the tail of a model this large to be 2 or more ounces lighter or heavier than average. One ounce of extra weight in the tail has to be countered by about 3 ounces in the nose. Don't use a lot of finish or excess glue on the tail surfaces. The motor you choose, what form of muffler is fitted, the size and placement of your radio equipment, etc. all affect the balance. Don't feel 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, the Cub should fly with only minor trim changes required.

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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 new model.

A properly balanced and aligned model with a reliable engine and radio is assured of successful flights.

26.

Flying

The Cub is not difficult to manage on the ground or in the air. However, being 1/4-scale and a taildragger, there are some differences you should be aware of between flying the Cub and flying most trainer or pattern type models. It handles more like a full size airplane than most smaller models.

When taxiing the Cub on the ground be prepared to use the elevators and ailerons in addition to the obvious rudder steering and throttle inputs. When the winds are calm, hold full up elevator while taxiing in any direction, to keep the tailwheel in firm contact with the ground for effective steering. Leave the ailerons in neutral, steer with the rudder, and control ground speed with the throttle. Under windy conditions, also hold up elevator when taxiing either upwind or crosswind. When going downwind, put the elevators in neutral or partly down to keep the wind from getting under the tail and flipping the Cub on its nose. Aileron deflection may also be needed while taxiing crosswind to keep the upwind wing from lifting off the ground.

Line the Cub up in the middle of the runway for takeoff. If you haven't had much taildragger time, it's best to stand directly behind the model so you can easily see any changes in heading that will need to be corrected during the takeoff run. Leave the elevator in neutral. Advance the throttle smoothly to full open. As the tail lifts up on its own, the Cub will try to drift to the left from torque. Feed in right rudder as needed to keep the model going straight. When you have flying speed, pull back slightly on elevator stick for a gentle liftoff.
During the takeoff run, try not to overcontrol the rudder (the most common rookie tailwheel pilot's mistake) which will start the Cub swerving from one side of the runway to the other.

If you find yourself in that situation, pull the throttle back to full low and get the model stopped. Taxi it back for a fresh start. Never try to hurry the model off the ground by pulling full up elevator just because the model isn't going straight! The damage from a premature snap roll on takeoff would be much more severe than anything that could happen on the ground. Actually the Cub is one of the easiest taildraggers to takeoff that you'll find. Just keep practicing your takeoff run without lifting off until you learn to use the throttle, elevators, and rudder together.

In the air you'll find the Cub smooth, stable, and responsive. With practice it is capable of doing most basic aerobatic manuevers such as inside loops, rolls, spins, and snaps. After you've had a chance to get the model all trimmed out, practice making your turns by coordinating rudder commands in with the ailerons, as is done in a full size airplane. Proper coordination of the rudder with the ailerons will make for a more graceful turn.
Landing the Cub directly into the wind or under calm conditions is pretty much like landing any other scale model. Be careful not to let the nose get too high during banks with the power off. Either wheel landings or three-point landings can be made with the Cub.

Just remember to fly the model even after it touches down (or you'll ground loop so fast it will make your head spin). Once the tailwheel gets back on the ground you'll have good steering and the model will slow down fast.
If there is any amount of crosswind, even quartering, landing the Cub (or any other taildragger) becomes a little trickier. Proper coordination of the ailerons and rudder is again needed to maintain your heading. After the model is turned onto final approach, use the rudder to hold the model on a straight heading with the runway and feed in aileron to correct any drifting to the side. For example, with a crosswind from the left, you'll need to hold a little right rudder to correct any "crab" angle (the model will be trying to weathervane into the crosswind) and put in left aileron to keep the model from drifting to the right.

If all these hints make it sound as if the Cub is difficult to fly, it really isn't! In many ways flying quarter-scale is easier than flying a faster, smaller model. The Cub can be safely flown by anyone who is capable of handling a multi-channel model. Once you get a few flights under your belt, you'll find rudder/aileron coordinated flying becoming second nature - and you'll be a better pilot with all types of models.
GOOD LUCK!

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