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Re: Biplaneraptor



Dann Pigdon wrote:
> 
>  I suspect that
> streamlining of the hind legs via feathers may also contribute to
> reducing drag in a similar way. I'm no expert on aerodynamics, but a
> gradually trailing edge would seem to reduce eddies forming behind a
> structure, while something more cylindrical in shape probably wouldn't.

An appropriately streamlined structure can reduce drag to approximately
1/25 that of a cylindrical shape.  But the Microraptor feathers do not
appear to be optimal for that purpose.  A t/c ratio between 3 and 5
would seem to be more appropriate for that purpose (for visual
comparison, a cylinder has a t/c ratio of 1).

> 
> It seems to me that the only way to prevent yourself from being
> 'butt-heavy' while flying or gliding when you have long legs is to > sweep 
> them backwards like those of a stork 

Um, let me see...... It appears that you are saying, "If I got too much
weight back there, I'll solve the problem by putting even more weight
back there".  How does that help?  :-)



> (and a long counter-balancing neck would probably help).

This is one of those cases where you can remove the word 'probably'.


> If Microraptor's skeletal structure precluded it
> from sweeping its legs back, and given its very un-stork-like neck, then
> perhaps streamlining the legs was a good compromise.

Two issues in the sentence above.  One, you seem to have the w&b issue
bakerds, and two, why do you assume that Microraptors leg feathers
provide much streamlining?  If I were selecting for streamlining, I'm
not sure I'd go the Microraptor route.

> If they had some
> moderate amount of lift as well, then maybe they functioned like the
> tail of a kite, helping to lift the rear end so as to point the entire
> animal in a more horizontal direction. A slight twist of the legs near
> the end of a flight/glide may have negated their streamlining/lifting
> abilities, thus orienting the animal in a more vertical plane for
> landing on a target tree trunk.

You're aware of course, that most animals and other craft that fly by
means of wings usually need a tail download to compensate for the usual
nose-down pitching moment of the wings -- not a tail upload.

Some pterosaurs are a rare exception to that rule, and they still
generate a net tail download by lifting with the hindlimb/tail, but
deliberately producing less lift than the weight of the legs.

> 
> Again, I'm no aerodynamic expert, so perhaps my aimless musings are well
> off the mark...

Welcome to the club.  I wouldn't claim to know much about aerodynamics
either.

All the best,
JimC