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Re: A few questions about pterosaur anatomy



ee555 wrote:

> > The angle of the pteroid bone ........If it was closer to ninety degrees
> > could it have been used to control the angle of the leading edge of part
> of the membrane?

It'd be more likely that that position could have resulted in
catastrophic flutter of the propatagium.  I know a guy that tried
something similar with a hangglider.  He only flew it once and only for
a very short distance. And there's no need for that positioning anyway. 
Among its other functions, the pteroid can be and is used to control
leading edge camber while pointing inboard.  As you're most likely
aware, a little adjustment in leading edge camber goes an awful long
way, and a lot can result in an unflyable craft.  For example, the chord
on the Piper Cherokee wing is about 63 inches.  The airfoil section is a
65sub2-415.  Installing a leading edge cuff that droops the nose of the
leading edge by about 1/4 inch in the front 4 inches of the wing results
in lowering the indicated stall speed by about 4 or 5 knots (the actual
stall speed isn't reduced quite that much).  It also lowers the cruise
speed by about the same amount.  drooping the leading edge by the amount
that you suggest would make the aircraft unflyable.  The results
wouldn't be all that much better on a pterosaur.  Plus, it would move
the suction peak very far forward at slow speeds (high aoa), and there
don't appear to be any structures present to transfer that load from the
pteroid back into the skeletal spar.  It seems to me that it would
counterproductive in the extreme.  And as an aside, it doesn't appear to
be consistent with the pteroid and wrist articulations in Quetzalcoatlus
(that area of the Quetz wing is quite well preserved).  The pterosaur
wing can achieve a steady-state CLmax on the loose order of 2.2, about
35% better than the best a bird can do.  There's not much need to
increase the steady-state CLmax any further than that anyway, as these
animals usually fly at a CL of roughly about 0.7 to 1.1.

Chris wrote:

> That sort of reconstruction was championed by Frey and Riess (1981.  A new
> reconstruction of the pterosaur wing.  Neues Jahrbuch für Geologie und
> Paläontologie Abhandlungen, 161(1):1-27.) and subsequent papers by Frey with
> various other people.  I do not accept their reconstructions, but what do I
> know?
> 
> > How extensive was the decline of pterosaurs through the Cretaceous? How
> many
> > families were left and is it true that most groups under a metre in wing
> > span had been out-competed by this time? Does this trend extend back into
> > the Jurassic?

There doesn't appear to be enough evidence in the fossil record to
support that hypothesis.  Or to disprove it.  If anything, the record
may infer that pterosaurs blocked birds out of the large soaring niches
(note that I don't necessarily believe that position either).

JimC