Presenting the 21st consecutive Air Trails trophy-winning model.

Detailed plans for duplicating another N.A.A. champion that flew

out of sight at the 1937 Detroit National Contest.

By Bernarr Anderson

in collaboration with

Gordon S. Light

THE BALFOUR TROPHY contest is for stick models and is open to modelers in the open class - over 21 years. This trophy was first put into competition in 1935 at St. Louis. Since then competition for it has been a feature of every national contest. The Balfour is intended to maintain the active interest of entrants after they are no longer eligible for the Mulvihill - the stick model trophy for modelers under 21 years. Success of this idea is indicated by the annually increasing list of entrants.

Bernarr Anderson of Akron was the 1937 winner at the national meet in Detroit. His model turned in a flight of 12:52. Unfortunately it was lost on the winning flight. Photos had not been taken, and it was impossible to check the drawings against the model itself. Luckily, however, Anderson had his original drawings, and a short time after the contest he revised them to include some last-minute changes he had made in the model. The plans have been made as nearly identical as possible to Anderson's model as it was on its winning flight.

This model is classified as a stick model despite the built-up fuselage. However, the addition of a landing gear would qualify it as a fuselage model, making it eligible for both contests with relatively little change.

CONSTRUCTION

The fuselage is of square cross-section. Consequently both side and top views will be identical. The fuselage is used in the conventional manner - that is, the wing is mounted directly atop the flat surface. It is not set on edge in diamond fashion. Longerons and bracing are medium-hard balsa 1/8 x 1/8", except the outline of the front and rear openings, which are strengthened with 1/8 x 1/4" balsa. The nosing is cut from a solid block of balsa (1-1/8 x 1-7/16 x 1-7/16) to fit the front of the fuselage. The rear of the fuselage is detachable, fitting into the fuselage in plug - like fashion and secured with hooks and rubber bands. The hooks for attaching the nose plug and tail boom are bent from fine piano wire. All other wire fittings are made of #16 piano wire. Rubber hooks are covered with 1/8" spaghetti tubing to prevent cutting.

WING

The wing is made in two halves and joined to form a flat center section. The ribs are cut from 1/32" sheet and are spaced every inch. Each tip is given 1-1/8" sweepback in addition to 4" dihedral. The center section is covered on top with 1/32" sheet. The top and bottom of the leading edge of the wing are covered with 1/32 " sheet. Ribs are sunk into the trailing edge 1/8". The two halves are joined by cementing flat pieces of 1/16" sheet to the sides of the spars. The detail drawing should make this step clear.

Both tips of the wing are washed out. That is, warp up the trailing edges of both sides of the wing. Looking from the rear of the wing, warp the left trailing edge slightly more than the right.

In covering the wing, the tissue should be loose (not wrinkled) from the leading to the trailing edge, and tight front tip to the center section. That is, stretch the tissue lengthwise along the wing, allowing it to be slack across the width of the wing. After covering, spray with water and let dry. Follow with three coats of thin (lope (3 parts thick dope with 1 part thinner). After doping rub down with the finest sandpaper available. (10 nought preferred). Sand the leading and trailing edges, wing tips, and all corners - as well as the tissue itself.

TAIL SURFACES

A lift section is used in the elevator and a symmetrical section in the rudder. Construction and covering are similar to the methods used in the wing. The rudder is cemented atop the elevator. (The bottom rudder rib being carved to rest atop the curved surface of the elevator). The rudder is braced by two short balsa struts 1/16 x 1/8 (streamlined) x 3".

The tips of the elevator are washed out, similar to the wing. However, looking from the rear, the right half of the elevator is washed out slightly snore than the left. The rudder is set at neutral - the offset thrust of 3° being sufficient to offset the thrust.

PROPELLER

The propeller block is 1-5/8 x 2 x 16-1/2". The blank is marked off as shown and the blades are cut to rough shape. Use the full-size pattern when cutting the outline of the blades. A ball-bearing washer is used between the propeller and the nose block. 3° right and 3° downthrust are used. The propeller should be sanded and doped to a glossy finish. The freewheeler is the type which is favorite among Ohio modelers, having been used on Lanzo's and Korda's winning models previously presented in this department. One edge of a small metal lug is bent down and pressed into the hub of the propeller. The other end is bent up and engages the shaft of the propeller. When free-wheeling, the shaft slips over the bent-up end.

The rubber motor is 18 strands of 1/8" flat brown rubber 40 inches long. Lubricate the rubber with a mixture of 50-50 tincture green soap and glycerin. Both of these are available at a drug store and make an effective and economical lubricant.

FLYING

The wing rests flat atop the fuselage. No incidence block is required. Attach with rubber bands passing over the center section and around the fuselage. Adjust the wing position so the model balances at a point about 2-1/2" back from the leading edge of the center section.

The elevator is cemented directly to the top rear of the tail-boom. Because of the slope of the fuselage it will be necessary to block up the trailing edge. The block should be of sufficient height (about 5/16") to raise the rear edge about 1/8" higher than the leading edge, as measured from the center line of the fuselage. After the elevator has been firmly cemented to the boom it will be possible to make minor changes in its setting by inserting small slivers of balsa between the tail-boom and the rear of the fuselage. Insert balsa at the bottom of the tail-boom plug to correct diving tendencies. And an insert at the top of the tail-boom will decrease the negative incidence of the elevator and correct tail-heavy tendencies.

The model has a steep, fast climb. Like most present-day championship jobs, it doesn't waste any time getting "upstairs." The circles are opposite torque - right circles with a right hand propeller. The offset thrust call be adjusted to circle the model in 100-foot diameter circles during the climb. The washout in the wing and elevator prove helpful in obtaining a smooth and efficient flight during the propeller run and during the glide.

MATERIALS REQUIRED

(Balsa used throughout)

Fuselage

Wing

Elevator and Rudder

Additional Items