Douglas O-43A (oz14018)

About this Plan

Douglas O-43. Scale model for rubber power. Wingspan 19-1/2 in.

Quote: "Build the Douglas O-43A, by Howard G McEntee. Full Instructions to Build and Fly a Flying Scale Model of the Latest US Army Observation Plane.

THE model we are now to make is called the O-43A. It is a two-seater observation ship of very high performance. There has been a long series of these ships built, each succeeding one with some worthwhile change, until the highly efficient ship as it now stands, was created.

Due to the use of an in-line, liquid-cooled engine, the streamlining of the fuselage is very fine with its narrow nose and small faired radiator. There are two radiators, one just back of the nose and below the fuselage, and the other, a larger one, for the Prestone cooling system, also below but somewhat farther back between the landing gear struts.

The landing gear is of the latest single strut type, the upper ends of which are well streamlined into the body. The ship is very good from the model builder's viewpoint because of the high wing and large fin, which make for fine flying qualities.

The original ship carries a pilot and gunner or observer. The gunner is provided with the usual flexibly mounted guns to the rear of his cockpit. The position of the stabilizer, set in the fin and quite a ways above the fuselage, provides very fine visibility aft and as a result any attacking ship would have a dangerous job to get in the coveted 'under the tail' position.

Some of these ships are equipped with a sort of turret which is seen just below the observer's cockpit. On others, this turret cannot be seen.

The ship is powered with a 675 hp Prestone cooled motor. The performance figures are of course kept secret, but keeping in mind the high power available and the excellent streamlining used, the top speed must be around 200 mph or over.

The fuselage of the O-43A is metal-covered, and to simulate this properly and get the smooth appearance, we use the hollowed out balsa construction. For those who have not tried this type of building, it is really not as difficult as it may seem and the writer believes that it is much easier than the built-up type. Once the balsa block is selected and prepared, the fuselage can be made in an evening, completely finished and ready for the attachments.

Two blocks 2-1/2 x 1 x 13 in are needed. Care should be used to select smooth, soft wood and not the harder stringy variety which is not as easy to cut. The blocks are lightly glued together, spreading the glue only along the center line of the blocks. This is done so that they will come apart easier when the fuselage is finished on the outside. The blocks should be clamped together or put under weights to dry. When dry, we are ready for the actual carving. Trace out the outline of the finished fuselage on the top of the block and cut to size. When this is done, repeat with the side outlines and cut to shape. The best way of doing this is to cut the patterns out of stiff paper and trace around the paper on the block.

We now have a block whose cross sections are all rectangular, but whose outlines are those of the finished fuselage. The next step is to round the edges off to the finished form. This should be started with a sharp knife, but after the first rough cuts are taken, coarse sandpaper should be used, as with this it is impossible to gouge too deeply and spoil the block. Several templates are given on the drawings from which cardboard templates can be prepared and which will be a big help in getting both sides alike.

The finishing off of the fuselage block should be done entirely with sandpaper, using finer and finer grades until the surface is very smooth. When this is completed, give the whole block a good coat of banana oil, which will of course raise the grain of the wood somewhat. Allow this to dry thoroughly, then sand again to a smooth surface. The block can now be split along the joint, using a razor blade only, never a knife.

The hollowing out can be done completely with a single 3/8 gouge. It should be sharpened very frequently with a slip-stone as the ease of the job depends to a great extent on the sharpness of the gouge. The walls may be cut to a thickness of 1/16 from the cockpit back and 1/8 forward. The nose section should be left quite thick to give strength and to balance the finished model. By holding the shell up to a strong light, any thick places may be spotted and cut down. The work can be smoothed down with sandpaper, but there is no need to try for a glass smooth surface, except the section at the cockpit and this should be well smoothed.

The three bulkheads may now be cut and glued in place. They are made in halves and must be cut to fit. No sizes are given for them on the drawing as every model will be slightly different in cross section. The centers must be cut out large enough to allow the rubber free passage without touching..."

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