The leading edges of the empennage and elevator hinge line are capped with 1⁄8 × 1⁄4-inch balsa strips (above left) and rounded off. Elevator is joined to stab
with flex nylon hinges at four places. The wing (above right) has a 2-piece spar Construction tips
Construction
Before beginning, take a look at these spe- cial tips for working with cardboard. Glue: Water base glue, such as white glue or Titebond, is recommended. Contact ce- ment is not recommended since parts cannot be shifted when gluing surfaces. Folding: The scoring of the fold lines is done with a screening tool available at any hardware store. It consists of a handle with a 11⁄2-inch radius wheel at one end, which is run along a metal straightedge on the fold line.
Finishing: Cardboard gives a solid sur-
face with no open areas to cover and is non- porous. The easiest finishing method is to give two coats of clear dope, sanding lightly between coats with #400 sandpaper, fol- lowed by two coats of color dope. However, a wide variety of finishing materials may be used on the cardboard. Coverings, such as Solarfilm, MonoKote and vinyl paper can be used. With any of these, it is recommended that the surface not be doped, which will re- sult in a better bond. Paper tape: All seams, joints and ex- posed edges of the model are covered with strips of gummed paper tape. Obtain a one- inch wide roll from a stationery store. Sim- ply cut a thin strip to length, dip it in water and smooth it over the seam.
Be sure to note the direction of the corru- gations when cutting out the cardboard parts. Score and fold cardboard parts as in- dicated on the plans. Empennage: The fin, rudder, stabilizer and elevators are each made from two pieces of 1⁄8-inch cardboard laminated together crossgrain to give 1⁄4-inch thick surfaces. Add a 1⁄8×1⁄4-inch balsa strip to the fin lead- ing edge and round it off. Add 1⁄8 × 1⁄4-inch balsa strips to the stabilizer leading and trailing edges and the elevator leading edge and round them off. Join the two elevator segments together with a 1⁄4-inch dowel. Seal all raw edges with gummed paper tape. Hinge the elevators to the stabilizer with flex hinges at four places. Notice that there is a 1⁄4-inch balsa fairing between the elevator segments which will be glued to the fuselage at a later time. Wing: Make the left and right wing spar sections from 1⁄4-inch balsa capped with 1⁄4- inch square spruce strips. Join the spar seg- ments together with 1⁄8-inch ply joiners, front and back, making sure to maintain the correct dihedral. Glue the 1⁄8-inch ply gear mount into the bottom of the right wing pan- el. Glue the wing spar into the right wing panel. The wing ribs 1 through 6 are then added, with the ribs at the ply spar joiners
comprised of a 1⁄4-inch light balsa web capped top and bottom with 1⁄4-inch square spruce strips. Note cardboard ribs, leading edge folds, 1⁄8-inch ply spar joiners at dihedral break and ply gear mount inserts.
being shortened by 1⁄8 inch to account for the joiner thickness.
Add cardboard doublers (two pieces) over each ply gear mount. Glue a one-ounce weight to the right wing tip. The top wing panel on the plan is slightly oversize, so fold the top wing panel over and trim it to fit the bottom wing panel. Apply glue to the top of the wing spar, the top of the ribs and the trailing edge of the wing and fold the center top wing surface down and pin securely in place until dry.
Build the left wing panel in a similar fash- ion. Add the balsa tips to the wing and sand to shape. Make a line guide from 1⁄8-inch ply. Cut a slot in the left wing balsa tip and glue the line guide in place. Cover the trailing edge and all seams with gummed paper tape.
Fuselage: The flat fuselage sides are out- lined with a triangular symbol on the draw- ing and include a slot for the horizontal sta- bilizer. Each fuselage piece is scored and folded near the leading and trailing edge of the wing. Line the upper and lower edges of each fuselage side with 1⁄8 × 1⁄4-inch balsa strips, as shown in the fuselage side view. The strips are recessed 1⁄8 inch in from the fuselage edges, except over the wing saddle area where the strips are flush with the edge of the fuselage.
The wing tips are carved balsa with a 1⁄8-inch ply line guide inserted (at left). Note gummed paper tape along the joint. Flat fuselage sides (above) are lined with balsa strips recessed 1⁄8 inch and have cardboard supports for the bellcrank and the fuel tank ply mounts. Note cutouts for flying wires and elevator pushrod.
FLYING MODELS 51
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