Re: Ruben Strikes Back

["James R. Cunningham" <jrccea@bellsouth.net>]

Dinogeorge@aol.com wrote:

> , taking full advantage of light weight and gravity assist for
> gliding.

Light weight isn't really an advantage in gliding.  Rather the opposite.  For 
the
usual range of lift coefficients (roughly from about 0.3 to about 1.1), 
increased
weight has no significant effect on glide ratio or distance traveled.  For a
given wing area, increased weight just increases the speed of the glide, so that
the heavier animal reaches the ground at the same point as the lighter one, but
more quickly, with the consequence that more distance can be covered per unit
time, thereby making the heavier animal more efficient in its ability to forage
(or escape, or whatever).  This has the effect that, for a given wing area (and
aspect ratio), the geographic area available to the heavier animal per unit time
is greatly increased.  Racing sailplanes carry water ballast to substantially
increase their weight for much the same reason, though they focus more on the
advantages of covering ground faster along an approximate ground track.

Jim