Re: WING FEATHER ATTACHMENT

["Tim Williams" <twilliams_alpha@hotmail.com>]

Jim Cunningham wrote:

> An animal with this arrangement of wing feathers wouldn't be a very
> efficient glider, however, because of the low lift-drag ratio.(PTN)
>
> I tend to disagree with this, since there's nothing about this
> configuration that would make the lift-drag ratio take a substantial
> hit (induced drag would be increased at a given airspeed and
> interference drag would be reduced, resulting in a probable increase
> in optimum airspeed, in order to reduce the induced drag
> contribution),

But surely the fact that there is a non-continuous lift surface across the 
body (as a result of the substantial gap between the distal wing and torso) 
means a *lower* lift-to-drag ratio.  I have modern patagial gliders (flying 
squirrels, colugo, etc) in mind when suggesting this.


> and the high wing loading would also make the animal
> glide at a relatively high airspeed, which would increase the
> territory covered per unit time, which I take as an advantage.

But for improved maneuverability to be the major selective advantage behind 
the development of the primordial wing, a *slower* airspeed would be better, 
wouldn't it?  The aim is not so much to travel a long distance but to land 
with greater precision - i.e. for the theropod to land upright on top of the 
prey, rather than to land on its fanny with the intended prey laughing its 
little head off.

In other words, for both lift *and* maneuverability to be selected for, 
wouldn't you expect to see (1) feathers along the inner wing to meet the 
torso (to provide a continuous lift surface across the body, a la modern 
gliders); and (2) feathers along the outer wing (the wing-tip) to provide 
maximal leverage against the air (to provide optimal orientational 
stability).

Cheers, Tim



------------------------------------------------------------

Timothy J. Williams

USDA-ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163



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