Stearman 4E (oz12701)

About this Plan

Stearman 4E. Peanut scale rubber biplane model.

Quote: "The 'Bull Stearman' is one of the most colorful and best looking of the 1930 era biplanes, also makes an interesting Peanut for builders with some prior building and flying experience. Stearman 4E, by Tom Cadogan.

In the January '79 issue of MB, Peter Westburg referred to the Stearman 4E as one of the sexiest bipes of all time. I couldn't resist turning his excellent scale drawings into Peanut plans and building my own replica of this Depression era beauty. This included duplicating the red, blue, and silver Standard Oil of California paint job shown in the two-part series. The result was very gratifying and I think you will enjoy building the Bull Stearman.

My approach is not for beginners, but if you've built a few Peanuts you should find some of these techniques interesting and simple enough to achieve. The primary challenge, if you're after realism (and with scale you should be), is to keep the structure light so you can afford the extra weight of the paint. My solution is to use 1/64 sheet balsa, condenser paper, and Floquil paints. The completed model weighed 16 grams less the motor. The weight prior to finishing was 14 grams, so surprisingly, the finish and decals added only two grams. The total weight of the craft, including the 1/8-inch rubber motor, was a shade under 5/8 of an ounce.

A good Peanut design will require little to no added weight to achieve balance. Of course, the choice of subject has a lot to do with this, but there are ways to maintain the balance problem of a short-nose airplane. Choice of structure helps, keeping heavier elements toward the front. Another is to move the center of lift aft by increasing the amount of lift in the tail section. The best way I have found to do this with Peanuts is to increase the surface area of the stab and elevator 15 to 20 percent. Balance is attained when the center of lift and the center of gravity coincide. This approximate location is shown on the drawing. On my model, no additional weight was required.

CONSTRUCTION Before you start, assuming you don't already have one, get a cork-surfaced bulletin board for a building surface. These are an excellent aid to construction, as they take pins easily and remain true. You'll especially need one for the fuselage formers and other curved pieces, as I'll explain later.

Begin with the wings by cutting the ribs from 1/64 sheet using a 1/32 ply-wood template. The use of 1/64 sheet is perhaps the only unusual thing about the wing construction, and a few precautions are necessary. Make sure you use a non-shrinking adhesive, such as Titebond, and don't try to force the ribs into position. I used sheet at the wing tips, around the strut connections, and at the center to provide an extra measure of strength at key places. I feel this is necessary when condenser paper covering is used because of the paper's low tensile strength. I would also suggest sheeting the leading edge of both wings, though I didn't do this. Before you set the wings aside, make sure the angle of incidence is the same throughout each panel. Corrections can be made when you shrink the wing covering.

The tips of the wings and stabilizer and the outline of the fin are constructed from 1/20 square balsa. The balsa is soaked in laundry ammonia, rolled around a row of pins embedded in your building board, and pinned down to dry. For me this technique is simpler than cutting cardboard templates or making intricate laminations, but again, the cork bulletin board is essential for success.

The fuselage is begun by pinning down the 1/16 square outlines shown in diagonal shading on the plan, and cementing on formers 5-1/2 and 10. both cut from 1/32 sheet. The center 1/16 stringer is added next, leaving a 1/4-inch overhang at former 5-1/2. When this is dry, formers 6 through 9 can be slipped into place under the stringer and cemented in an upright position. These formers are also made by soaking in ammonia and bending along a row of pins. The remaining stringers are cemented in, extending each across former 5-1/2. Formers 4 and 5 are added, and the stringers broken, bent and cemented to the bottom of former 5 as shown on the plans. The fuselage half is removed when thoroughly dry, and the other side added in similar fashion. The landing gear wire is inserted, followed by the 1/64 sheet covering at the nose and around the cockpit. The landing gear shown is scale, but if you wish the Peck-Polymer prop to clear the ground..."

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