[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: big, slow, pterosaurs



I disagree with the last line:

"The trade-off would have been an extreme vulnerability to strong or turbulent 
winds both in flight and on the ground, akin to modern-day paragliders."

Paragliders have a lot of problems with strong winds because:

#1) A lack of pitch control
#2) Light wing loading

Hang gliders have about double the wingloading, and pitch control, and fly in 
winds exceeding 40 mph, while paragliders don't really fly in much over 15, 
maybe 20 mph. I don't think these Pterosaur would be limited to those winds, 
and thus the comparison to Paragliders understates their capabilities.

I would also think they could modify the shape of their wing much more than PGs 
can, and certainly more than paraglider - and would also be more capable of 
handling turbulence than hang gliders and paragliders.

Paragliders also have a nasty tendency to collapse in turbulent air. This is 
something that wouldn't happen in Pterosaurs.

And of course, they could flap enough for powered flight (even if the flapping 
was limited in duration)




--- On Wed, 5/11/11, Mickey Rowe <mickeyprowe@gmail.com> wrote:

> From: Mickey Rowe <mickeyprowe@gmail.com>
> Subject: big, slow, pterosaurs
> To: dinosaur@usc.edu
> Date: Wednesday, May 11, 2011, 5:14 PM
> http://rspb.royalsocietypublishing.org/content/278/1713/1881.abstract?etoc
> 
> Palmer, C. (2011). "Flight in slow motion: aerodynamics of
> the
> pterosaur wing", Proceedings of the Royal Society B,
> 278:1881-1885.
> 
> Abstract
> 
> The flight of pterosaurs and the extreme sizes of some taxa
> have long
> perplexed evolutionary biologists. Past reconstructions of
> flight
> capability were handicapped by the available aerodynamic
> data, which
> was unrepresentative of possible pterosaur wing profiles. I
> report
> wind tunnel tests on a range of possible pterosaur wing
> sections and
> quantify the likely performance for the first time. These
> sections
> have substantially higher profile drag and maximum lift
> coefficients
> than those assumed before, suggesting that large pterosaurs
> were
> aerodynamically less efficient and could fly more slowly
> than
> previously estimated. In order to achieve higher
> efficiency, the wing
> bones must be faired, which implies extensive regions of
> pneumatized
> tissue. Whether faired or not, the pterosaur wings were
> adapted to
> low-speed flight, unsuited to marine style dynamic soaring
> but adapted
> for thermal/slope soaring and controlled, low-speed
> landing. Because
> their thin-walled bones were susceptible to impact damage,
> slow flight
> would have helped to avoid injury and may have contributed
> to their
> attaining much larger sizes than fossil or extant birds.
> The trade-off
> would have been an extreme vulnerability to strong or
> turbulent winds
> both in flight and on the ground, akin to modern-day
> paragliders.
>