Hi Paul,

As I understand it there will be no pulling force acting
on the inside of the canopy. This is admittedly counter-intuitive
to anyone who tried the following bored-in-science-lab
experiment; if we place a pipette against our skin
and release the nipple, our skin feels as if it is
being pulled towards the low pressure. In fact the
higher pressure inside our flesh is pushing our flexible
skin towards the low pressure area.

Back to gliding, which always tends to distance itself
from the world of skin and nipples, this does imply
that any minute pockets of trapped air in the canopy
might pull- sorry, might cause the very insidemost
parts of the canopy to be PUSHED in towards the low
pressure within the suction cup, potentially damaging
the canopy. However, I presume such pockets don't exist;
there would be visible depressions in the canopy where
these pockets had cooled after the forming of the canopy,
and any such pockets would be just/almost as prone
to deforming the canopy during a high wave flight.

Without the existance of air pockets, I reckon the
situation would be just as I described before - complete
with disclaimer..

Simon

At 21:24 12 April 2007, Paul Remde wrote:
Hi Simon,

I don't think the issue is how much pressure the outside
air pressure can
put upon the outside of the canopy. The issue is that
the suction cup is
shaped like a ... well... a cup. It has enough force
to pull the canopy to
form to the shape of the inside of the cup. That causes
local stresses on
the canopy. It may or may not be a visible deformation.

Paul Remde