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Re: FW: The "ideal" Eumaniraptoran arm motion



Hi,
I think you guys may be slightly overestimating the amount of drag involved.  
To roughly quantify it, a 360 pound animal with a 36 foot wing, moving at 45 
mph and carrying its full weight with its wings, would generate about 15 pounds 
of drag (half profile, half induced). This applies whether the wings are 
feathered or membraned.  Were he to unload his wings, the induced drag 
component would go to zero, leaving only 7.5 pounds of profile drag, 3.75 
pounds on each wing.  This describes a big animal.  A smaller or slower animal 
with shorter arms would generate much less
drag. At what point does the drag become inconsequential?  For that matter, by 
flapping a bit, pronating on the downstroke, and supinating appropriately on 
the recovery, the animal can make net thrust exceed net drag, to the tune of 
about 1/3 g available for horizontal acceleration in the direction of choice.  
At what point does net thrust become consequential?
Best wishes,
JimC
P.S.  Although its obvious that the lift and drag parameters mentioned above 
are roughly those of Q northropi flying at L/D max,  I certainly don't mean to 
imply that I think that animal could run at that speed. Or at any speed for 
that matter.


Jeffrey Martz wrote:

> <Still, biological life forms must obey physical principles. They atmospheric
> <friction, drag, whatever, that would be caused by cardboard or feathers,
> <whatever, would tend to slow down the arms as they are swept forward in <the 
> "ideal" prey catching motion that maniraptorans were capable of.
>
> [Jeffrey Martz]
>      Sure, but would it slow it down enough to prevent it from catching 
> something small and fast?  If increasing the area of the insect net increases 
> insect catching more then drag on the feathers decreases it, then it might be 
> a worthwhile trade-off.  I not necessarily trying to defend the insect net 
> idea, which can be objected to for a number of reasons.  I've never been 
> crazy about playing the "what if" game with flight origins.  My point was 
> that humans slapping cardboard together might not be the best model for 
> theropods snatching at something with their arms.
>      In any case, I'm not certain that those who suggest that maniraptioran 
> adaptations in the wrist were for prey catching are thinking in terms of 
> insects and insect nets, or even having prominent feathers on the arm at all. 
>  I believe Ostrom proposed that idea for the origins of large feathers on the 
> hand and forearm, not pectoral girdle and wrist adaptations (which would have 
> come earlier).
>
> LN Jeff