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Re: Science feather strength debate

It is also worth noting that the inboard wing is more involved in weight 
support of the animal, while the outboard wing is more involved in the 
production of the thrust component of lift (note that in flying animals thrust 
is just a forward component of the lift, which is itself just the component of 
fluid force perpendicular to flow).

Without a complete wing inboard, there is a significant loss of weight support, 
as a result.  There is also a substantial increase in induced drag, as the 
inboard wing then represents a second, broad, "wingtip" around which a downwash 
can form.  This further changes the flow on the wing because it tends to shut 
down spanwise flow, which then weakens certain forms of vortex stabilization on 
the wing.


--Mike H.

On Nov 14, 2010, at 11:13 PM, Tim Williams wrote:

> Jason Brougham <jaseb@amnh.org> wrote:
>> Yeah, also, what exactly is the aerodynamic function of tertials? A wing
>> is not a sail or a  parachute. The feathers closest to the armpit move the
>> slowest and the least far during a flap, so do they even generate any
>> lift?
> Yes, during flight the tertiaries "fill the space" between the body
> wall and the secondaries.  In doing so, they allow a continuous flight
> surface to be maintained, and thereby increase the lift-to-drag ratio
> of the wing.  Because the humeral shaft tends to be quite short in
> extant birds (relative to the distal elements), not many tertiaries
> are needed.
> Also, when the wing is folded, tertiaries cover the secondary remiges
> (which  in turn cover the primaries), so they have a protection
> function.
> Augusto Haro <augustoharo@gmail.com> wrote:
>> Agreeing with your opinion, as far as I am aware, as the bird humerus
>> is surrounded by muscle in a greater measure than the ulna, it is to
>> be expected that the plumage is not so firmly attached to the skeleton
>> at this point, and it may thus be more easily disarticulated with
>> decay. Correct me if I am wrong, but I never read or saw first-hand
>> humeri with feather knobs, while they can be found in the
>> carpometacarpus in addition to the ulna. If true, the lack of these
>> feather attachment structures may suggest feathers were not attached
>> to the humerus.
> Yes, that's my understanding too, Augusto.
> Cheers
> Tim

Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
(443) 280-0181