Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site psivax.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!vax135!cornell!uw-beaver!tektronix!hplabs!sdcrdcf!psivax!friesen
From: friesen@psivax.UUCP (Stanley Friesen)
Newsgroups: net.origins
Subject: Re: astronomers, flesh and blood gliders, out-of-context quotes
Message-ID: <739@psivax.UUCP>
Date: Wed, 18-Sep-85 18:31:46 EDT
Article-I.D.: psivax.739
Posted: Wed Sep 18 18:31:46 1985
Date-Received: Mon, 23-Sep-85 00:39:03 EDT
References: <395@imsvax.UUCP>
Reply-To: friesen@psivax.UUCP (Stanley Friesen)
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 59
Summary: 

In article <395@imsvax.UUCP> ted@imsvax.UUCP (Ted Holden) writes:
>
>
>               There are  several kinds  of animals on our planet which can
>          glide, but are not  generally capable  of flying.   These include
>          the flying  squirrel, the  flying fish,  and one  or two kinds of
>          lizards.  In  each  of  these,  gliding  is  basically  an escape
>          mechanism which  they use  occasionally to  get out of harms way,
>          and which they use to cover small distances, typically 50  or 100
>          feet.   The  flying  fish  and  lizards  must  jump vigorously to
>          achieve their shorts glides,  while the  squirrel takes  off from
>          trees.  None  of these creatures RELIES on gliding as its primary
>          mode of transportation and, in  that  sense,  there  are  no true
>          gliders amongst  the animals  of our planet.  There are none now,
>          there have never been any, and there never shall be any.
>
	This is somewhat misleading, there may be no *pure* gliders
which rely on gliding for transportation, bu there *are* a number of
animals that are *predominantly* gliders. These include the Albatross
and many(or even most) Vultures, especially the giant Vultures called
Condors. These animals have sufficient musculature in thier wings to
wupplement gliding with an occansional flap(to provide that small
extra push needed to stay aloft). The wing structure of the larger
pterosaurs(such as Quetzalcoatlus and Pteranodon) is very close indeed
to that of an Albatross. In short the comparison of these organisms to
Flying Squirrels and the like is an apples/oranges comparison.
>
>>Langston is not describing the same behemoth which flies by
>>expending large amounts of power flapping its wings that Ted does.
>>For a gliding animal such as Langston postulates, large amounts of
>>wing power are not required, as the necessary lift comes from thermals.
>>True, getting airborne is not easy, but Langston proposes a plausible
>>mechanism, well known from living (though smaller) creatures.  Once 
>>airborne there is no reason why *Quetzalcoatlus* could not have 
>>remained aloft all day, as unpowered sailplanes do today.
>
>
>     Now, we've  all seen vultures take off from low ground by simply spreading
>their wings and ascending  into the  rising heat  waves coming  off the ground,
>haven't we?   I mean, these guys seem to be describing the Texas pterosaur as a
>prehistoric  G. Gordon  Liddy,  with  superman  cape  attached,  only  the real
>G. Gordon Liddy  at least  had the sense (if you could call it that) to try his
>stunt from the roof of his uncles barn.   The technique  didn't work  for Liddy
>(who spent  several months  in the  hospital) any better than it would have for
>Quetzalcoatlus Northropi, which outweighed Liddy by about 100 lbs.
>
	But it *does* work for the larger Vultures(how many times have
yoy even *seen* a Condor, let alone watched one take off?).  Mr Liddy
didn't have the advantage of fantastically light bones like birds and
pterosaurs. Also, he probably was using the wrong wing proportions.
This is where the thrice mentioned *low* stall speed calcualated for
these animals becomes important, it is what allows this to work.

-- 

				Sarima (Stanley Friesen)

UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen
ARPA: ttidca!psivax!friesen@rand-unix.arpa