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Re: Coelurosauravus: glider? or bluffer?



  Not to remark to long on engineering principles, but the narrower the
diameter of a spar the more likely a given pressure with effect to distort
it. In a wing, this is NECCESSARY as can be seen in birds wings where the
individual feathers respond to pressure from the air by bending upward
and/or backward, deforming their "resting" state; a rigid structure is
more likely to fracture under a similar load as a flexible one, and for
this reason, modellers tend to form their structures from many small spars
forming a whole than one single large plane, as in a bat's wing (spars on
joins), bird's wing (spars with overlapping planes), or an aeronautic wing
(simple plane with slats that reduce pressure at given points). So ... 1)
for a given length, a narrower diameter will distort more than a broader
diameter; 2) a bending element will respond to stresses better than a
rigid one; 3) a broad element exhibiting great stresses will tend to break
more than that of a narrower element.

  And ... the amount of stress being exerted on a given area for a given
mass decreases with a decrease in size, so that *Coelurosauravus* is not
really under a whole lot of stress gliding. The same amout of pressure
would affect *Draco,* who does just fine.

  Dave questioned the use of the spars in *Coelurosauravus* because they
are of a dermal origin, but I'd like to point out that so are all
vertebrate ribs. Forming extra dermal structures is not going to decrease
the viability of these spars as an airfoil. Both the fossil *Icarosaurus*
and the living *Draco* show adequate mechanisms for controlling stress on
their expanding ribcages, so *Coelurosauravus* shouldn't be that much
different.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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