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Re: Fw: Archie a non-flyer? (was:Re: origin of bats/reply 2 to TMK)
On Wed, Jun 25, 2008 at 9:50 AM, jrc <email@example.com> wrote:
> --My original post responded to your comment that asymmetric feathers reduce
> drag by asking, " By what mechanism does it reduce drag?"
> Your response was, "By avoiding turbulent airflux."
> I took that to mean avoiding both turbulent attached (high drag) and
> turbulent seperated (very high drag) flow, which implies laminar flow. Since
> the feathers don't see significant laminar flow, that triggered my series of
Indeed my original response could be interpreted that way. It would be
better that I've said "by avoiding partially turbulent airflux" or
more properly "by reducing turbulent airflux".
>> Drag *over* the wing could help creating lift (or, eventually,
>> thrust), but drag *behind* wing, in most case is not a good idea.
> --Could you elaborate on that, please?
That model is more well stablished for insect flight.
> --Asymmetric feathers shift the point of maximum t/c ratio forward, with the
> usual results. However, shifting it aftward usually results in lower drag.
> I would speculate that the evolution of asymmetric feathers had more to do
> with reducing feather mass than reducing drag or increasing lift.
Reducing feather mass? Reducing feather total area?
>> Does any one have created a mechanical model of a avian wing with
>> symmetrical and assymetrical feather to see what happens during a wing
>> stroke? Or have simulated it in computer?
> Not to the best of my knowledge. However, with the exception of mass
> effects (and at very high lift coefficients), the wings would operate much
> the same even if the individual feathers were shaped like planks,
With no effect on airflux?