Convair XP-81 (oz13914)

About this Plan

Convair XP-81. Control line scale model of the experimental fighter prototype.

Quote: "Scale control-line that combines realism with simplicity of building, flying. Convair XP-81, by James Metzger.

Here is a model that combines realism and simplicity to obtain maximum endurance and an attractive appearance together with handling ease comparable to that of a trainer.

The only prototype of the Convair XP-81 was first flown on February 11, 1945, but with the end of the war in sight, further work on the project was cancelled. This trim looking beauty was designed as a long range escort fighter for bombers in the Pacific, and to be powered by two engines: a turbojet in the tail and a turboprop in the nose.

At the time of its first flight however, the turboprop was not available and a Merlin engine from a P-51D Mustang was sub-stituted giving it exceptionally fine handling characteristics. This explains why an alternate nose configuration is included in the plans. The tuboprop configuration was chosen as the principle design for the model since it allows for more efficient engine cooling as well as slightly easier starting.

This is certainly a rare and unusual aircraft, and photos and scale drawings are just as rare. By some stroke of luck, a three-view drawinb showed up in some old flying magazine and from this the original plans were drawn. A very good photo was obtained from the Convair Company on request, and served as an excellent reference for outside detail.

With these items as the only guide, the model was completed in about three months of rather unsteady work. It was designed for a Fox .15 more for convenience than anything else. A .35 requires quite an investment in materials as well as a sizeable storage space; whereas with a 1/2A, details and good flight characteristics are difficult to obtain. A .15 seemed to be the best solution and resulted in a very satisfactory model that combined the desirable qualities of the other two power categories.

Of course, the biggest thrill of any modeler is the actual flying of his craft and it is certainly quite exciting to have control of a scale ship that handles just like the real thing. Although not designed to do stunts, this XP-81 is a bit on the heavy side, (17.4 ounces) but it takes to the air with the professional look of a hot fighter. With about an eight foot run, it can leap off the ground in a relatively steep climb, or if desired, a slow steady climb can be obtained with just the right amount of up control.

Its 29 inches of wing span give it sufficient area for high speed and maneuverability. Level flight is extremely smooth and reaction to any command is very definite with virtually no worry about over-controlling. With moderate engine speed, powered landings and takeoffs can be performed with fantastic realism, but of course, these should only be attempted on a smooth surface.

When powered by a Fox .15 turning a 7-6 nylon prop, the top speed is around 75 miles per hour. Dead-stick landings are the most difficult procedure since this plane will not glide as lightly as most free-flights or stunt ships, and care must be taken not to stall out. A good landing can be obtained when the engine cuts out while in level flight, and with just a slight bit of up control the plane will settle to the ground with the main landing gear touching first followed shortly by the nose wheel. Flying lines should be between 35 and 50 feet for best results.

About the only adjustment that would have to be made for better flight is in the balance point. Some weight may have to be added to the tail to bring the balance point to about 3/4 of an inch behind the leading edge, but extreme care must be taken to prevent the plane from becoming tail heavy which would make it very difficult to control.

Construction is relatively simple since the overall design of the plane is quite smooth with mostly flat surfaces and gentle curves. The biggest difficulty will probably arise in the air intake construction and fuselage planking. The first steps in building are the cutting out of the fuselage formers and attaching the two long ones to the round ones to obtain the general contour of the fuselage as well as a foundation to work from..."

Convair XP81 from MAN, April 1963.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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