Rocket Delta (oz7146)

About this Plan

Rocket Delta. Free flight model for Jetex power.

Quote: "The first full scale delta-wing aircraft was developed and flown in Germany, back in the early 1930's by a very creative gentleman, Mr Alexander Lippisch. Serious delta development by Lippisch and associates began in 1929 with the Mk-1 glider model. They tried some sixteen-pound thrust rockets on the larger models (ten-foot span) and had exciting results. Then a full scale delta glider was flown in 1930 and performed quite well. An engine was later added at the rear. The aircraft gave an excellent public demonstration in 1931.

These early designs had only moderate sweepback, about twenty degrees, but they were tailess flying wing airplanes. They led Lippisch to the famous Me-163 Komet, a rocket-powered swept wing tailess fighter which, in 1941, had an unheard of rate of climb (13,000 feet per minute) and an equally fantastic level speed of 625 mph.

In 1943, following wind tunnel tests of a new high speed wing shape, he designed the P-13, a sixty degree delta, as we know it today. It was a step toward supersonic flight, many years ahead of its time.

I was very fortunate to be working with Dr Lippisch from 1950 to 1959 after he had come to America. Some of the delta business rubbed off, on me.

The aerodynamics of delta wing aircraft are most curious. Did you know, at low speed and high angles of attack, lift is generated only by the leading edges of the wing? A huge vortex rolls down along the outer edges of the wing, and swirls out behind in a long trail. On some of the six-foot span glider models you could actually hear the low roar of vortex formation as they swished past us.

You will find also, there is a transition period from low to high speed flight, where there is a momentary shift of center-of-pressure as the lift changes from the outer edges over to the usual laminar flow on the whole wing surface. This phenomenon can give you some rather hairy take-offs.

The flat plate wing section used on our model has proven to be very good for Jetex flying. It has excellent high speed characteristics, yet hangs on quite well at high angles of attack. A stall builds up gradually, then the delta makes a quick recovery. It will dutch-roll slightly when flying near the stall. It was necessary to arrange a balance of lateral areas fore and aft of the CG to maintain spiral stability. The profile cabin is actually a sort of front fin.

Before beginning construction, decide on the type of flying you wish to do. For contests a light model will climb higher and fly longer - if you can control it. But this trick of making the model do what is right, is not so easy. A heavier flying machine is usually more stable, lasts longer in rough conditions, and sometimes ends up flying better. Your choice of materials will determine the weight.

Build up the hollow triangular leading edges, and trailing edge first. Use medium weight (8-10 lb) C stock. It is best to use thin glue on these parts. Be certain they are straight after drying. Round all edges slightly. Assembly of the flat plate wing is easy if you have an old drawing board to work on. Be sure it is not warped. The center rib of 1/4 in square should be hard balsa. Put the trailing edge on correctly so it slants upward from the bottom.

Cover wing before final assembly of parts. Use standard tissue for a light model. Silkspan or bamboo paper is more durable for the heavy duty model. Cover only half the top at a time. Start by attaching the paper to the leading, edge..."

Direct submission to Outerzone.

Update 07/07/2016: article pages, text & pics added, thanks to RFJ.

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