Feathercopter (oz15735)

About this Plan

Feathercopter. Simple free flight helicoptor model.

Quote: "You know that the Wright brothers developed the first practical, man-carrying, heavier-than-air flying machine, and made the first successful flight on December 17, 1903. Sure. But do you know what originally fired their imagination with the possibility of mechanical flight? A toy helicopter. In 1878, when Orville was seven and Wilbur eleven years old.

Helicopter? In 1878? That's right; about the time your great-grandfather was in fifth grade, Bishop Wright bought a toy helicopter for his sons and triggered a line of thinking that was to change the world, and is still doing so. The toy was based on the 187? designs of Alphonse Penaud, a Frenchman, and what may be even more surprising is that his design, while including one important invention, was a modification of something almost 100 years older!

A working model helicopter at the time of the American Revolution? Right again. The story goes like this: In 1768 Paucton, a French mathematician, pro-posed what he called a 'pterophore', which had one airscrew to lift it and another to drive it forward. There is no record that either a full-scale, man-powered machine, or a model, was ever tried, but apparently the idea inspired two more Frenchmen, Launoy and Bienvenu. They invented what they called an 'Automoteur' (I call it a Feathercopter, for obvious reasons) and demonstrated it to the French Academy of Sciences in 1784. As one history book states, it held their attention. It should have, for this was the first known machine capable of lifting and sustaining itself in free flight. It proved that mechanical flight was in fact possible, something that no one was entirely sure of up to that time. It was not a kite, depending on the wind to hold it aloft. It was not a glider, which cannot rise except on thermals and strong up-currents. It was not a boomerang or missile, which must be thrown. It was a true flying machine, lifting its own weight by means of its own whalebone-bow power source.

Sir George Cayley experimented with feathercopters in England in 1796 (George Washington was still President) and doubtless many other inventors as well, but no real improvements were made until 1870, when Penaud re-designed it to two-bladed form. Much more importantly, he also invented the rubber-band motor, and it was this development that made the difference between something that merely worked, and a practical flying model capable of remarkable performance.

The Histories say that a feather-copter will 'rise to the ceiling,' and that is just about all the author's reconstruction is able to do. That it flies is certain, but 5-second flights are not too impressive nowadays. On the other hand, Penaud's helicopters (the term had been coined in the 1860s) would rise to 50 feet or more... for a period varying from 15 to 30 seconds. They still do, and much more. That, along with the difficulty of obtaining good feathers, is the best reason for building a Penaud model. If it started the Wright brothers thinking, what might it do for you?

Construction of the Penaud is very simple. The most important point, perhaps, is in selecting good balsa. The 1/8th square for the frame must be as straight-grained as possible, and the harder, the better. If you feel the balsa begin to crush as you pinch it, look for something harder, it probably won't take maximum wind-up without twisting badly and possibly even breaking. Pre-glue all joints and after gluing spread a cement skin over the joint area as a final strengthener, especially around the balsa-aluminum hub.

For a good, close-fitting joint at the hub, first cut a shallow 'V' along the length of the balsa component. Then wrap a piece of fine sandpaper around the tube and work it back and forth until the 'V' is transformed into an arc which exactly conforms to the curva-ture of the tube. For the upper, fixed hub, the tube is simply glued in place. For the lower, driven hub, the wire shaft must first be inserted, bent over, and embedded before the tubing is glued one. And don't forget the washers.

The blades should be of soft or medium 1/16th sheet. It is important to remember that you are dealing with a push-me-pull-you affair where the upper prop is right-handed and the lower left-handed..."

Direct submission to Outerzone.

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