On Monday, September 29, 2003, at 12:11 PM, Julian Vincent wrote:
> Colin Penycuick did a paper many years ago in J Exp Biol looking at the
> bending of the tip of a birds feather and relating it to energy storage
> at the end of the wing stroke.
> But it's easy enough to set up the rachis as a cantilever beam and
> twang it to get a resonant vibration. Record with high-speed video
> (these days) or shine a light through a slit and have the rachis cast a
> shadow onto some photographic paper (a way I did this with grass yonks
> ago. Also described in the book on experimental techniques with
> biological materials - IRL press. Or do it on a strip of material in a
> torsional pendulum (again easy to set up) at a number of temperatures
> (-20 in a freezer to + 40 under a heat lamp would be quite possible.
>
But... added mass.... likely significant for a lightweight structure
with an aerodynamic function and tuned torsional stiffness. Pennycuick's
technique avoided those problems at least.
Cheers,
Adrian Thomas
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