About this Plan
Twiddler. Twin Jetex-powered sport helicopter model.
Quote: "Try this little whirly-bird for real flying fun with 2 Jetex 50 units. Twiddler, by Ray Morse.
It is Ray Morse's aim to try to advance the design of the model helicopter, and during the past few years he has conducted a series of experiments in spare time from his normal duty of running a fine holiday camp on the Broads. Working on one's own is a slow uphill job, however, in the end patience is rewarded, and the design shown here is the result of a long series of tests.
This little helicopter employs the Clough type pivoted rotor blades, but instead of being powered by a diesel on rotor hub, it is driven by twin Jetex 50 B units. As far as we are aware it is the first to use Jetex power with the Clough blade system and we think you will agree that this little machine is not only pleasing to the eye, being reasonably scale-like in appearance, but it also offers several virtues on account of its small high-revving rotor, this being only 15 in diameter with four blades, as you will note. High revs make for increased gyroscopic stability, markedly noticeable in strong winds, as well as greater jet efficiency operating at higher speed. Another advantage is that the jet units are carried on the piano wire extensions of the blade pivots, thus deleting the separate beam mounting as used on the two-blade helicopters.
Details opposite are half-size, but for those who prefer actual size details a 2s 6d plan is available.
Begin by shaping the fuselage lower block from balsa and cementing at right angles to 1/4 sq balsa rotor mast support, then sandwich in between 1/32 med sheet balsa sides, cementing together along tail boom. Fill cockpit back, also top and bottom of the fuselage with 1/16 sheet. Attach the 1/32 sheet in hard balsa tail vane with aluminium wire or strip. The skid under-carriage is made as follows. Cut the two skids from 1/16 sq bamboo, heating ends to form upturned tips in candle flame. The 20 swg wire legs are formed after heating to cherry red to assist bending. Cement skids to legs and bind with fine cotton. Glaze cockpit with thin acetate sheet after adding interior details to cockpit such as seat and stick.
Rotor: The four blades are cut from 1/16 med sheet balsa, and sanded to section as shown, keeping trailing edge as fine as possible. Attach mass balance weights and all pivot bearings with cement, afterwards binding with tissues or strips of Jap silk. Mass balance weights are made by looping the end of 20 swg wire, binding with fuse wire, then building up with soft solder to streamline form. Finish with emery cloth, or better still, file to shape in the lathe if you have one. Be sure to make all the weights identical, otherwise the machine will fly in banked circles at low altitude, due to unequal feathering. The bearings, of approximately 0-024 inch sheet aluminium are formed with clips to press into balsa. blades when cementing. Assemble rotor hub upside down on a scrap block of wood for location..."
Twiddler, Aeromodeller, July 1958.
Direct submission to Outerzone.
Supplementary file notes
Article pages, thanks to RFJ.
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