Re: The origin of flight: from the water up (still short!)

["David Marjanovic" <david.marjanovic@gmx.at>]

----- Original Message -----
From: "James R. Cunningham" <jrccea@bellsouth.net>
Sent: Wednesday, March 27, 2002 9:16 PM


> When they're gliding it is gravity that generates the thrust, not the
wings per
> se.  If you need to carry more weight, you simply increase the rate of
descent.
> For a given wing (ignoring structural strength issues) if you need to
carry
> twice the weight, you simply increase the rate of descent by about 41%.
> Flapping and continued level flight are a different issue.

Thanks for the details; I am talking about flapping and continued level
flight (though no flapping in Superman).

> > Because Big Q has a few more elements that can grow, such as the wing
finger,
> > I assume.
>
> Oh.  I had assumed it may have also had something to do with mechanical
loading
> of the skeletal spar and membrane.

May all be <desperately trying to show off with my ignorance, or something
like that>. Anyway, birds have 4 segments per wing whose proportions can
respond to different demands: upper arm, forearm, hand and primaries, while
pterosaurs have 7: upper arm, forearm, metacarpus and the 4 wing phalanges,
so pterosaurs may be able to distribute the stress differently. An analog
may be that compared to any running dinosaur running ungulates have very
short shanks, but longer metatarsi, and they are unguligrade, so they have
an extra limb segment for functional purposes.

> > Oh, sorry, I'm talking about moving underwater. When the tail is too
long
> > there, it requires excessive power to be moved (except in the plane of
the
> > rectrices).
>
> Why is it relatively much different than in air?  At these speeds, both
are
> incompressible fluids and dynamic lift and drag forces are changing
> proportionally to the density (a factor of about 800).

That's it -- moving a long, stiff plate (Archie's tail) through water is
harder than moving it through air, and the longer the plate is the harder
that becomes. Doesn't it?

> Do we know that the tail
> mobility was constrained such that it was impossible to use the tail
feathers to
> move the tail in more than the pitch axis?

No AFAIK, and I didn't suggest that. I just imply that Archie's tail was
most mobile at the base, while the rest was a pretty stiff rod, like in
"dromaeosaurs".

> > I don't think so. I'm just suggesting a possible test, cheaper than a
wind
> > channel, for how having an Archie tail influences manoeuverability in
water.
> > :-)
>
> Doesn't this presume that a rigid, artificial archie tail functions
identically
> with a living tail?

Oops...

>  Are are you planning incorporation of internal mobility to
> make the hypothetical simulation more 'realistic'?

I should. Anyway, due to the lack of a suiting material (and the difficulty
to get a cormorant... there are some in the nearby national park, though), I
won't do it anytime soon. :-)