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

Re: avian flight



> > >   I can't speak for Jim Cunningham, who's aeronautics and
> > > mathematics specialty is well above mine.
> >
> > And mine, and maybe even above Ebel's...
>
> Oh pleease -- I don't know diddly about this stuff.

I have the impression that nobody really knows much, because e. g.
turbulences and suchlike are very important, but hardly at all computable,
but you surely know more "about this stuff" than most or all other list
members. (Any lurker out there who...?)

> > >   I strongly disagree. Lift is less than drag in a parachuter,
> > > and there is no thrust, thus lift is directly opposed to drag.
> > > The animal drops.
>
> I lost track of who said the above, but parachuting is generally defined
as a
> descent with a glideslope less than 1:1.  Parachutes can and do generate
> considerable thrust, and modern paragliders can actually glide with
glideslopes
> up to about 5 or 6 to 1, perhaps better (I don't keep up much with
paragliding).
>
> > Weight pulls the parachuter downwards, and drag pulls it upwards, so
drag is
> > "lift"... As there is no lift
>
> How do you define the forces when the parachutist is adjusting the chute
to
> provide a horizontal component so that he's not descendiing straight down?

I don't know what Ebel makes of this, he includes a forward component in his
figure of the acting forces during parachuting, but he doesn't mention
anything in the text. (One more reason people should read this paper...
:-) )

> > OK. That's more or less what I've wanted to describe, only in much
detail and
> > very slowly... and I'm getting tired, my English is leaving me.
>
> Shucks, you speak it better'n us southern american boys.  Our grammer
ain't all
> that good even when we'uns don't be tired.

Forget grammar, there's hardly any left in English anyway, but vocabulary is
a problem for me when I'm tired.

> > (We don't have _any_ gliding animals in Europe... :.-( )
>
> Yes, you do.  They hang out at the glider ports.  I'm seen 'em.  Some of
the
> world's best sailplanes are designed, built, and flown in Europe by some
of the
> world's best pilots.

So exactly I have fallen into the trap of pre-Linnean paraphyletic
animals... Shame. What I wanted to say, of course, is that there are no
gliding squirrels, gliding marsiupials, dermopterans, *Draco* etc. around
here. (Normal red squirrels there are.) Neither are there parachuting
snakes, frogs, geckos...