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----- Original Message -----
From: "Michael Habib" <email@example.com>
Cc: "DML" <firstname.lastname@example.org>
Sent: Friday, September 16, 2005 6:08 PM
Subject: Re: Pro(to)avis
1) The limbs may have been held subhorizontal, but still held close enough
to a horizontal plane to generate lift.
If the outboard feathers were less stiff than the inboard in bending, it
would enhance this effect.
2) The hindlimb feathers may have more important to increasing passive
stability than to generating lift.
To be passively stabilizing with anhedral, the hindlimb feathers would need
to be creating a download rather than upwardly directed lift. Some aircraft
do that, but I doubt that an animal would deliberately create a substantial
download for any extended period of time.
A number of different hindlimb orientations (other than splayed
horizontal) might accomplish this goal, either by producing some
differential lift laterally when the animal tilts,
This would require dihedral if the hindlimb feathers were lifting; or the
anhedral you postulate, if the hindlimb feathers were downloading.
or by simply increasing posterior drag such that the animal had a tendency
to stay facing forward. (The problem with these ideas is that the
increased drag would make it harder to stay in the air).
Creating lift with the hindlimbs either lifting or downloading in a
subhorizontal orientation would do this anyway, due to the increase in
induced drag as the hindlimb aspect ratio decreases.
3) It could simply be a developmental constraint, or be unrelated to
flight...but I'm not sure how to demonstrate these very conclusively.