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Fwd: Gliders to Fliers? (Was Re: Ruben Strikes Back)



 
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George is right about the stabilizing, but I speculate (and I emphasise 
speculate)
that, early on, the tail may have been used to carry a substantial fraction of 
the
weight of the legs, perhaps 10-15% of the body weight.  Of course, due to the 
low
aspect ratio, this tail lift would come at the expense of very high drag, and
would also serve to stabilize the animal.  Later, as flight ability evolved, in
order to reduce the massive drag, the tail would be more likely to be unloaded
when not providing command authority. As I'm sure you both know, the tail of an
aircraft normally does not lift.  It is used to create a substantial download in
order to resist the nose-down pitching moment of the wing, and the wing carries
the weight of the aircraft plus the tail download.  For example, my PA28-150
cruises with the tail generating about a 200 pound download, about 10% of the
weight of the aircraft.  When the CG is shifted aft enough to reduce the tail
download requirement, the plane becomes very squirrely, unstable in pitch, to 
the
point it can become impossible to control.
All the best,
Jim
P.S.  Would one of you guys forward this to the list for me.

Dinogeorge@aol.com wrote:

> In a message dated 10/1/99 4:44:34 PM EST, ptnorton@email.msn.com writes:
>
> << The problem I have with the concept of the tail being the first aerodynamic
>  surface to develop is that it would place the center of lift for the
>  unfortunate animal well aft of its center of gravity; which would cause it
>  to tumble in a---well---an ass over tea-kettle motion. Not particularly
>  adaptive.  A more probable gliding scenario is one that would select a
>  critter with a center of lift at or near the animal's center of center of
>  gravity.  This is precisely what we see in all extant quadrapedal scansorial
>  and/or arboreal gliders. >>
>
> The tail didn't do much lifting at first; it helped to stabilize leaps
> through the air between branches, much as the fletching on an arrow keeps its
> trajectory under control. When wings started to develop, the already useful
> tail helped to stabilize the trajectory like the tail of an aircraft does.
> Here tail lift is more useful and would be selected for.




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