Laird Biplane (oz2824)

 

Laird Biplane - plan thumbnail image

About this Plan

Laird Biplane. Scale 15 in span FF biplane, all sheet balsa, CO2 powered, by Dick Struhl MAN Dec 1950.

Quote: "ONE of the cleanest biplanes to appear in the 1936-37 era was the Laird R300 light cargo carrier. Based upon the Laird Thompson Racer, this three-place utility model retained all the racing lines and performance of a Thompson Trophy winner. Powered with the Wright Whirlwind of 330 hp, this plane had a top speed of 175 mph and cruised at 155 mph. The landing speed was 50 mph, with a service ceiling of 20,000 ft.

We present our version of the Laird in semi-profile form powered with the Campus A-100 CO2 engine. The model is not completely drawn to scale. Certain liberties were taken from the true scale plans to insure a top-notch flying model. The dihedral angle, the tail surface area, the landing gear design and location, and other factors have to be modified in the interest of flying, and the result is well worth the cribbing from scale. Our little model has a very consistent stable flight path at all times and under all weather conditions. This little job has been flown on windy days when you wouldn't dare drag a larger model out of the car. And best of all, being so light, the plane is practically indestructible.

The strength and durability of the model is due to the sheet balsa type of construction employed. You can't beat this construction for small models, and if the material is chosen carefully, you can keep the weight of your model Laird down to 3/4 oz.

Study the plans well before you attempt construction. All parts are shown full size and in their entirety. No duplicating right and left panels!

Make the wings first. Trace the top wing onto a sheet of 1/32 balsa 2-1/2 x 15 in, marking the di-hedral breaks and the center line, but do not cut as yet. Do the same for the lower wing on a piece of 1/32 x 2-1/16 x 12 inch. Note that the dihedral break on the lower wing coincides with the center line. On the underside of the wings, brush on one coat of clear dope from the leading edge to a point about two-thirds of the wing chord. Set the two wings aside to dry. This procedure will automatically form the necessary airfoil camber in the wing when dry.

The fuselage is merely a thin rectangular box just wide enough to enclose the engine and tank. First, cut two fuselage sides from light 1/20 or hard 1/32 sheet balsa. On the inside portion of one, mark the position of the firewall and the two bulkheads. Cement the bulkheads and firewall in place on this side. Note that the firewall has downthrust built into it. Now cement the other fuselage side in place and check alignment. When the cement has set, fasten the fuselage top and bottom pieces in place. No bottom covering is used around the cowl and the portion of the fuselage just in front of the lower wing. This will permit easy removal and installation of the engine and tank. Bend the landing gear to shape from .038 music wire and cement in place to the insides of the fuselage side pieces. Apply several coats of cement and also dope a small piece of cloth over the joint for extra security. Carve the headrest from soft 1/4 balsa and cement in place.

The tail surface is cut from 1/32 flat sheet balsa. Note that the stabilizer is one piece, while the rudder is in two pieces—one piece entirely above the sta-bilizer and a smaller portion below the stabilizer. Rather than using a rudder cutout in the stabilizer, we merely apply black dope to that portion to sim-ulate the cutout for greater strength.

Now to complete the wings and assemble the plane. The wing panels should have assumed an airfoil shape when the dope on the underside dried and contracted. If not bent completely to shape, you can mold the sheet slightly with your fingers. Cut the panels apart at the dihedral breaks and install the proper amount of dihedral as shown in the front view. Cut two outer wing struts from hard 1/32 sheet balsa as shown in the side view.

When the cement has set, install the lower wing in place in the notch provided for it in the fuselage. Use two coats at this joint. Now cement the struts to the bottom wing and allow to dry. When the cement has set, but not dried completely, drop the top wing in place and, looking at the front and top views, check the alignment of the wings and fuselage. If any alterations are needed, now is the time to make them before they dry..."

Update 10/01/2019: Added article, thanks to RFJ.

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Laird Biplane - completed model photo

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Scaling

This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.

 

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