Re: Sort Your Story Out! (Was: 2 refs that were once new...)

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

Mike Taylor wrote:

> > Archie is out of this range but within that of flightless birds.
>
> I don't think this proves anything.  The fact that modern gliding
> birds have asymmetry within the range of modern flying birds is purely
> circumstantial -- plus it's the sort of convergence you'd expect,
> since an aerodynamically efficient feather is aerodynamically
> efficient whether used for flapping or gliding.

The interesting thing to me is that the argument for asymmetric feathers
appears to presume that most of the feathers are oriented transverse to the
relative wind -- but this isn't always the case.

> In fact, come to think of it, this whole feather-asymmetry thing is
> nothing more substantial than guilt-by-association.

Yeah.

>  Given that Archie
> was more primitive than modern birds, we'd expect it to be less well
> adapted to flight than they are.

Perhaps so, but the asymmetric question doesn't actually address how well
the feather was suited for flight.  That depends more on the orientation of
the particular feather with respect to the relative wind (and consequently,
with respect to the chordwise pressure distribution).  So far, I've not seen
anyone address that issue.  I tend to suspect that the asymmetry may be more
closely related to using the pressure jump between the upper and lower
surfaces of the feather to promote sealing between adjacent feathers, not to
mention venting between feathers when appropriate.

Jim