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Re: Arms into wings

It is well known that the airfoil shape is perfectly suited to the task of
providing lift on the wing of an animal or vehicle which is propelling itself
forward.  This ubiquitous shape is evident in avian primary remiges and 
(feathers), in the shape of the bird wing itself, as well as all manner of other
forms (including airplane wings, frisbees and propellers).  To demonstrate the
effectiveness of the airfoil (to a classroom of first grade students), I fitted 
styrofoam (polystryrene foam) airfoil shape with straws which enabled the form 
go smoothly up or down a set of brass rods.  The styrofoam rose with ease when 
electric fan directed a stream of air at the airfoil.  I had also attempted the
same with a flat block of styrofoam, for comparison, and it failed to rise.

The funny thing is that the airfoil rose whether the breeze was directed toward 
fore or aft end, as the curve remains atop the airfoil either way!  (On the 
hand, an upside down airfoil wouldn't work at all)!  Hence, even a symmetrical
feather would produce some lift; the familiar airfoil shape of modern avian 
feathers is "merely" an important refinement.  The _Caudipteryx_ feather style
would therefore confer some degree of aerodynamic function, in spite of its less
than optimal shape.  In actual flight, the trimmer leading vane of an avian 
feather would be sturdier in the face of the wind, and would be easier to 
than the broader vane (were the feathers to be reversed on a bird).

Ralph W. Miller III  <gbabcock@best.com>