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Re: What is biomechanics? (or, The Truth About Flying Snakes - Was: Re: science and philosophy)



I wrote:

<<Feathers, as comparative tests show, do not make an animal fly, even a
bird.>>

and Colin McHenry (cmchenry@westserv.net.au) wrote:

<But no-one said that feathers alone make the foul.  Did they?>

  Some have, and that was my point.

<In birds, flight feathers can generate lift at relative air-speeds (i.e.
the speed of the airstream over the surface of the feather - not the total
airspeed of the animal) that are low enough so as to be within the range
that a muscle powered vertebrate can induce by flapping its wings.  Even
flight feathers are not, on their own, a magic ingredient for producing
lift - they do so within a certain range of relative air-speeds and angles
of attack.  All feathers - and any other integumental structures - produce
drag.

It might sound like an obvious and silly point to make (and Jim, kick me
if I've got it wrong), but it is worth remembering because if you forget
it
then it can lead to some faulty logic, as in...>

  Indeed, I do not believe in the magic of feathers; a feather by itself
does nothing, not even produces lift. It is a feather in action that does
anything, and not just a single feather, but a arrangement. Similarly,
bats without feathers fly by stretched skin, rather than condensed
feathers....

<???!!!  But surely imposing drag - and lots of it - is exactly what a
parachuting animal needs its integument to do?  And this is a parachuting
animal, right?  I mean, just because it's called a flying snake, surely
no-one was seriously suggesting that it moved through the air by
lift-based
powered flight?>

  Nope ... quite the contrary ... that data I have contradicts it. I
myself never supported it. As I do not support *Longisquama* flying by any
present data. Or even gliding. So far, no study shows what appear to be
radiating slats could even produce a sustained drag or possess a paraxial
resistance to torque that would in anyway resist gravity.

<it's the way the snake moves that provides the ability to glide,
essentially a directionally-controlled descent.>

  Indeed.

<And paragliders do the same thing.  It's not gliding in the sense of a
glider 'plane, or a soaring bird, but surely most animals that get called
'gliders' - flying frogs, flying squirrels, sugargliders, for example -
are
really parachutists of some description (with varying ability to control
their descent)?  The only 'glider' that might be closer to a glider 'plane
that I can think of offhand is _Draco_.>

  I know of some references that have drawn differences in animals that
glad versus parachute, and the snake and frog are both considered
parachuters, but presently lack them myself -- I will try to look these
up. The distinction has been to support with anatomy a direction-based
definition, above or below 45 degrees.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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