Gull Wing (oz6253)

About this Plan

Gull Wing. RC sport pattern model for .60 power.

Quote: "I have always admired the cross country Thompson Trophy and Bendix Pylon racers of the thirties. The project presented here is an airplane I feel would have been competitive in that era. Good flying stability is accomplished by the shoulder high gull wing, and the egg crate construction makes building fast and simple, plus self aligning, if some care is taken in cutting out the parts. The fuselage and gull wing section were constructed first, followed by the outer wing panels and tail section. Everything went according to plan with only a few surprises.

A Fox Eagle .60 seems to haul it around in grand style. Ace rack-type servos are used in the wings for ailerons and flaps, with Ace and D & R Bantam servos for the throttle, rudder and elevators. An Ace receiver completes the airborne portion of the electronics. And my knees knock with a Heath GD- 19 transmitter in my hot shaking hands. When the antenna hits high C, I apply forward throttle and hang on; fortunately the airplane can fly better than I. As she hurtles down the runway and lifts into the air, I take a deep breath and the antenna drops to middle C - on a good flight I can play the Star Spangled Banner!

Construction is straightforward and should be interesting to scratch builders. All of the hardware is available from the local hobby shop.

Fuselage: The fuselage is an egg crate design. This method of construction eliminates the need for a complex building fixture, while producing a strong accurate assembly. If the bulkheads and main vertical and horizontal structural members are accurately cut, the fuselage assembles very quickly and accurately, with planking the only remaining task. All of the fuselage parts are cut from 1/8 sheet made by laminating 1/64 thick wing skins on both sides of 3/32 x 4 x 36 in sheets of balsa, creating a strong, stiff bulkhead. The stationary portion of the rudder, cockpit canopy, landing gear sockets and wing saddle are all integral parts of the fuselage.

The top forward part of the fuselage will later become the center gull section of the wing and is built together with the main fuselage. Bulkheads on the front and back end of the central section are temporarily held in place with a drop of contact cement. The central wing section and main fuselage are sheeted as a single unit. The wing spars that form the gull part of the wing are built into this central removable section. When the outer wing panels are complete, they are positioned and glued onto these spars.

Before the fuselage is sheeted, all internal work should be completed. This includes: throttle linkage, pushrods for the rudder and elevators, servo rails, and the three T-nuts that secure the central gull wing section to the fuselage. The nose piece, or cowl, is made up of balsa blocks glued to a 1/8 plywood backing ring. The backing ring has the identical shape as the firewall. Using a Dremel tool, the inside of the cowl was hollowed out for engine clearance. With both the engine and cowl bolted in place, the spinner was bolted to the engine shaft. Using the spinner as a guide, the exact diameter and position of the spinner was transferred to the front of the cowl. After removing the cowl from the fuselage, a 1/16 sheet plywood ring of the same diameter as the spinner O.D. was glued to the front of the cowl, using the spinner transfer marks for location. You now have the cowl with a sheet of 1/8 plywood on the back and a sheet of 1/16 plywood on the front. It is now an easy matter to carve and sand the cowl to shape.

The landing gear socket assembly is made of 3/16 plywood and glued into the fuselage. This completes the structural part of the fuselage and it may now be completely sheeted with 3/32 balsa.

Wing: The elliptical gull wing is of standard construction, with three main sections, the center gull section and the two outer panels. The two outer panels contain the ailerons and flaps. Movable surfaces are controlled with bellcranks, and Sullivan flexible pushrods activated by servos mounted into the thick section of the wing. Intercommunication between ailerons and between flaps is accomplished by running the pushrods straight through the gull section of the wing. This method eliminates secondary bellcranks or lever arms from a fuselage mounted servo. As an advocate of strength from wing skins, I have circumvented the need for heavy wing spars. The top and bottom of the center wing section are glassed with 2 oz glass cloth..."

Direct submission to Outerzone.

Update 14/4/2024: Replaced article with a clearer version, thanks to theshadow.

Supplementary file notes

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