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Re: More on Argentavis

--- jrc <jrccea@bellsouth.net> schrieb:

> ----- Original Message ----- 
> From: <gerarus@westnet.com.au>
> To: <marksabercat@yahoo.com>
> Cc: <dinosaur@usc.edu>
> Sent: Tuesday, July 03, 2007 9:07 PM
> Subject: Re: More on Argentavis
> > (it is not entirely
> > incorrect to say it becomes more like swimming
> than flying). This is
> > also why insects have flat wings rather than
> aerofoils.

I read about a study a few years ago dealing with
this. To accurately scale air viscosity for the
foot-long blowfly(IIRC) model they were using to study
turbulence, it had to be put into a vat of syrup.
Trying it in air would give anomalous results.
> Note that many insects, dragonflies for instance do
> have rather effective 
> aerofoils.  The veins are oriented to force the
> airfoil shape under load.

I find it interesting that in the size range of about
3-10 cm, hovering flight seems to have been far easier
to achieve than in larger or smaller animals.
Dragonflies, hawkmoths, hummingbirds, small passerines
(which don't have an adapted shoulder joint but still
manage to hover for some periods of time)... I'm not
sure, but small bats don't seem to do it; may have
something to do with the fact that their wings are
attached to the body over a long distance and don't
have sufficient freedom to move.

But from my totally unscientific observations of
living animals, I get the impression that wing
movement during hovering in dragonflies *looks*
different than in hawkmoths, let alone hummers.


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