Detail the Balsa USA 1/3-Scale Super cub

Model Airplane News, Jan 2000 by Viosca, Charlie

Scale building techniques from a master

ORIGINALLY REVIEWED the Balsa USA* 1/3-scale Super Cub in the June '98 issue of Model Airplane News. While this is a great plane, detailing the Super Cub will add much more to this miniature aircraft. It will take a lot of time and patience, but the result will make it all worthwhile. In this article, I discuss the installation of working cockpit controls, as well as a realistic instrument panel and side panels for the Super Cub; you could easily use these ideas on any large-scale cabin plane.

It's important to think ahead. For instance, when you build the fuselage, you should install the working cockpit throttles before you join the left and right sides. To do that, you have to install the servo mount and cut a groove through the left side for the throttle pushrod (see Figure 1). Remember, the cockpit controls do not have any control over flight. The controls-powered by Futaba* S-3103 micro miniservos-merely mimic the action of the flight controls.

SIDE PANELS

Make the side panels out of thin, 0.011inch aluminum sheet, from print shops or good hardware stores, sold as chimney flashing. Bend the top throttle cover as shown in Figure 1. The lower panel has holes for the fuel, magneto and trim panels as shown in Figure 4. Fasten the panels to the model with no. 2 button-head socket screws. The right side panel contains the door cutout. All of the aluminum panels should be black; the square magneto switch block and fuel selector valve, red; all lettering, white; the trim crank, silver; the magneto switch guards, black. The throttle balls should be 3/8 inch in diameter and painted black. Drill and tap them for 2-56 bolts. Be sure that the throttles have a clearance of 1/16 inch above the side panel when advanced and retarded.

FLIGHT CONTROLS

For the flight controls, refer to Figures 2 and 3. Cut an 1/8A-inch-thick, 14x8-inch-ply floor and install it, starting at former F2. The front floor is 6 inches long and 8 inches wide at former F2 to 6 inches wide at the front. It should be painted black. Glue 1/4x1/2-inch spruce crosspieces at the bottom of both sides of F2. Glue another crosspiece 8 inches back. The floor can be screwed to these pieces.

The flight controls are made of 1/4-inch brass tube. The control sticks are 5 inches tall and are bent slightly rearward at a point 2 inches down from the top. I used ball bearings on the aileron tube, but 1/4inch-i.d. tube is an acceptable substitute. Install the bearings before you solder the stick mounts to the aileron tube. A 1/4-inch brass strap holds the bearings to the pillow block. Mount the aileron servo on the floor just to the left of the tube so the front seat hides it.

For the elevator control, pass a 1/16-inch solid rod through the aileron tube and attach it to the front stick with a clevis. Solder a 1/16-inch pin to the rod to connect the rear stick; there isn't enough room for a clevis. Attach the other end of the elevator rod to the elevator servo. Mount the control sticks to the floor.

Fuel and trim panels are shown on Figure 4. Make a fuel knob by hollowing out a piece of Styrofoam roughly in the shape of the knob; then pack in some JB Weld*. When it's hard, cut away the foam and shape the knob with a motor tool. Drill and tap a hole through the knob for a 2-56 screw. When you mount the fuel panel, place a fiber washer between the panel and the knob, and put a fiber locknut behind the panel.

Make the trim panel so that it moves the indicator as shown in Figure 4. Use a small, 0.013-inch pull/pull cable and wind it so that the cable comes off the shaft at the bottom. Start by inserting the cable through the two small holes in the shaft, first winding the cable closest to the panel. Make three winds, then move to the pulley. Wind the other cable in the same fashion. Now you will probably need a helper. Take one cable and make a swage on it, then pass it through the small hole in the indicator. Now take the other cable, put a swage on it as well, and pass it through the first swage. With the indicator centered and the cables on the pulleys, pull the cables tight and hold them while a helper mashes the swages. Now you should be able to turn the knob, and the indicator will show the trim position.

Make the trim arm by flattening a piece of 1/8-inch brass tube, which will leave the ridge lines that you want. Solder this flattened tube to a 1/4-inch wheel collar. Bend it slightly toward the panel and solder a smaller collar to the other end. Use epoxy to fill the holes and also to give the large collar a tapered shape from the base to the top. Drill the large wheel collar and tap it for a small setscrew. Use the setscrew to attach the arm to the shaft.

INSTRUMENT PANEL

Cut the instrument panel as shown in Figure S. From left, the instruments on the top row are compass, artificial horizon, altimeter and clock. The ones on the bottom row are oil pressure, temperature, rpm, and turn and bank gauges, remote indicating compass, V.O.R./I.L.S. indicator and suction gauge. Balsa USA includes the glass instrument covers with instructions to paint the inside of the bezels black, but I recommend that you glue O-rings into the bezels.