Biot's Kite (1880)

 

This kite is an interesting French kite first shown in 1880 by a Frenchman named Biot. It is described in Lecornu’s classic volume Les Cerfs-Volants (1902), which seems to be the only source of information about it. The illustration is taken from that book.

The sail ABCD is framed and two rigid cones G and K are placed on each side, somewhat forward on the frame. At the aft end is placed a propeller, which replaces a tail, but has the same effect of acting as a brake or stabiliser by virtue of its gyroscopic effect. The dimensions given are AC = 38cm., the cones are 20cm. diameter with a depth of 18cm.; the propeller is 30 cm. diameter with blades 3.5 cm. thick.

Lecornu says that the kite showed stability in winds from 6 to 15 m/s (12 to 30 knots, Beaufort 4 to 6 or 7) and flew to a height of 2000-2500 metres.

The same picture is reproduced in Pelham (Penguin Book of Kites, 1976), where it is described as Biot’s double-coned rescue kite, though I don’t know on what authority it is thought to have rescued anybody (though I do know that a number of other kites of the time had been used for that purpose: a kite flown from land could take a lifeline out to a shipwrecked ship). Thiebault (Kites and other Wind Machines (1982)), an English translation of an earlier French book of uncertain date) also mentions the kite, though he adds no useful information about it (and also some of the dimensions given in his plan are clearly wrong, possibly because he misread Lecornu).

I have decided to make a version of this kite, though obviously there are some minor problems. The frame, I think, should be made of wood, since it is then going to be easier to attach the cones to it. Lampshades may suffice and it would be easy enough to staple them to the wood. Small propellers may be bought from model aircraft suppliers on the internet. The diagram does not show how it is bridled, but I guess a 3-point bridle attached at A, B and somewhere down the EF axis would work. Field experiments will obviously be necessary. As for the sail, I will start with Tyvek with perhaps washi paper as an alternative.