Douglas O-46A (oz4344)

About this Plan

Douglas O-46A. Rubber scale model.

Direct submission to Outerzone.

Update 27/08/2020: Added article, thanks to RFJ.

Quote: "Observation Wings. Complete plans for building a flying scale model of the Douglas O-46A army observation plane. By Alan D Booton.

THE Douglas O-46A observation is one of the most beautiful planes in the air to-day.- The admirers of military aircraft will soon have better chances of see-ing the new O-46As, as they are becoming more common with the army's order of 115 rapidly nearing completion.

The design is exceptional for a flying-scale model, the parasoled wing and fine streamlining providing efficiency and stability in flight. Like its prototype, the model has the same grace of line—both for display and in the air.

FUSELAGE: The fuselage is carved from solid balsa and hollowed. Select two 1 x 2 x 13-1/2 in soft blocks and cement them together with three drops of cement, so they may be split apart later. Scribe the side blank first. You will find that the block is not deep enough, but by sawing the rear surplus off and cementing to the bottom at the front, ample depth will result. Finish sawing the side, then scribe the top blank and saw.

Carve the shape with the aid of the fuselage sections, sand and dope to a smooth surface. Split the two halves apart and hollow them carefully to the thicknesses shown on the sections. Place the wood over a strong light to check the thickness.

Bend a rear hook similar to the one shown and cement it in position when the two sides are being recemented together.

The cowl drawing is simple and self-explanatory. Tile nose plug must be removable, but as much motor detail as desired may be added.

WING: The wing has been designed to retain the characteristic gull effect. Cut out the ribs and curved parts and cement them together, along with the leading edge, to form a complete outline. (It will be necessary to trace a right panel.) When dry, raise the whole outline 1/4 in with blocks and cement all the ribs in. When dry, crack the leading edge and trailing edge at ribs 2, and the leading edge again at 10, then block up in the final, position shown on the front view and apply plenty of cement to the cracks. Cement the 1/16 sq spars in.

After the cement has thoroughly dried, remove the frame from the form and sand carefully to the final shape, taking every advantage of the gull effect. Cover, the wing with orange tissue by attaching the outer edges of the paper first. Spray lightly and pin to the bench until dry.

TAIL SURFACES: Build the tail surfaces from unshaped stock and then sand to the final shape when dry. Cover them with orange tissue, using the method employed for the wings.

LANDING GEAR: Make the landing-gear struts of two plys of 3/16 sheet and sandwich the shock-absorber axle wire between. The shock absorber is arranged so the lower half of the strut will bend back and still not bruise the trailing edge at the joint. The tail wheel is cemented in place rigidly.

PROPELLERS: A scale-propeller design is included, should one be desired. The flying propeller takes advantage of the three-blade design, because of the limited diameter. Cut three blocks as shown, apply cement to the bevel ends and let dry; then apply more cement and then join the three blocks together, tacked to the bench. Let dry several hours and then blank and carve in the usual manner.

ASSEMBLY AND FINISH: Cement the cockpit cover on. Cement the stabilizer on and then the fin, and finish covering at bottom fin rib. Add the stabilizer struts. To get the wing on easily, cut a 1/8 sheet incidence block to the shape of the space between the wing and the fuselage on the drawing and pin the wing in position. The struts can then be cut and fitted accurately. Use bamboo slivers for the rigging 'wires. Cement the landing gear struts on. The model will have a better appearance if illustrated design for the wheel is used. Cement the cowl on as noted On the drawings.

Insert the prop shaft through the nose plug, several washers, and the propeller, make a small U bend in the end of the wire and push it into the wood and then cement.

A special 'S' hook has been designed so that the four-strand rubber motor can be attached "remotely" to the rear hook by holding the nose of the model up while the motor is being dangled into the fuselage. The rear hook is engaged by 'fishing' and disengaged by shaking. If the model is to be used for flying only, numerous coats of dope are not advisable, the dressed-up model will fly with reduced endurance.

FLYING THE MODEL: Glide the model into tall grass until satisfactory adjustments are made and reduced power flights are tried. If you desire a high-climbing model, substitute for the regular prop an 8 or 9 inch two-blader and add as much power as needed."

Supplementary file notes

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