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Water, thru ambient water pressure, compressing the
air inside the cabin or tank, changes the air displacement if you do
not
add any air to replace the compressed
air.
Bill.
----- Original Message -----
Sent: Wednesday, November 09, 2005 6:33
AM
Subject: Re: [PSUBS-MAILIST] Forces of
Nature
the bouancy should not change if the exact shape of the vessel
does not
change because it still displaces the same amount of water which
does not
become denser due to compression. therefore bounancy is about
displacement
not wether the air inside is compressed if you see what
imean
>From: "Akins" <lakins1@tampabay.rr.com>
>Reply-To:
personal_submersibles@psubs.org
>To:
<personal_submersibles@psubs.org>
>Subject:
Re: [PSUBS-MAILIST] Forces of Nature
>Date: Wed, 9 Nov 2005 00:59:57
-0500
>
>Hi Joe.
>
>Not sure if I am reading your
questions correctly, but I will try to help
>and hopefully be corect
for what I think you are asking.
>
>Remember that 1 atm is the air
pressure at the surface and is the 14.7 psi
>we have pressing against
our bodies (GENERALLY speaking) ALL the time.
>
>If you want
to submerge something to say 33 feet, that would be 2 atm.
>Remember to
count the
>
>single atmosphere we already have pressing on us all
the time. So 33 ft is
>2 atm, 66 ft is 3 atm, etc.
>
>You
asked.....#1 One submerges a bubble of air (enclosed in any material)
>and open to ambient pressure to 1atm . Equal forces of pressure are
applied
>to either side of the material. I assume that the lifting
force of the air
>in pounds of buoyancy is not cancelled out by the
equalization of that
>pressure. That the material is subjected to a
stress in psi equal to that
>force. Then if one were to apply an
opposing force ,as in ballast, that the
>material is then subjected to
both forces. Is this a correct assumption?
>
>The first part of
your question I assume you mean't submerging a bubble of
>air at
ambient pressure at greater than 1 atm.
>
>The second part of your
question states about applying equal force to
>either side of the
material. I assume you mean the water pressure force
>
>going into
the main soft ballast tanks or even part of the subs ambient
>hull
(depending on design) and then having equal force applied
by
>
>releasing air into the same space and therefore the material
(hull or
>tanks) has equal force applied onto it from both sides which
cancels each
>other's force
>
>out, remembering of course
that there has to be a slight pressure
>difference inside, in that the
inside air pressure force holding out the
>water has
>
>to
be slightly greater than the water's pressure trying to get in. That
>sounds correct if that is what you mean't. I wasn't quite sure what
your
>third part of the question mean't
>
>when you asked
whether the lifting force of the air was not cancelled out
>by the
equalization of that pressure. Are you asking if by pressurizing the
>vessel, (material, bubble, whatever) if
>
>the lifting
force of the air is decreased by being compressed against the
>outside
water pressure? If that is what you were asking, I am not the best
>to
answer this, but I do know that the deeper
>
>you go and the more
you compress air, it does have an effect on its
>buoyancy I believe.
I'll leave that one for someone a bit more
>knowledgeable in math to
compute buoyancy loss due to air molecule
>
>compression. But I
hope I helped you some, and remember we are always at
>approximately 1
atm all the
time.
>
>Bill.
>
>
>
> -----
Original Message -----
> From: Joseph
Perkel
> To: personal_submersibles@psubs.org
>
Sent: Tuesday, November 08, 2005 12:15 PM
> Subject:
[PSUBS-MAILIST] Forces of Nature
>
>
>
>
My learning curve is flattened again, too many distractions, Please help
>me with some basics here.
>
>
> #1 One
submerges a bubble of air (enclosed in any material) and open to
>ambient pressure to 1atm . Equal forces of pressure are applied to
either
>side of the material. I assume that the lifting force of the
air in pounds
>of buoyancy is not cancelled out by the equalization of
that pressure. That
>the material is subjected to a stress in psi equal
to that force. Then if
>one were to apply an opposing force ,as in
ballast, that the material is
>then subjected to both forces. Is this a
correct assumption?
>
> #2 One submerges a piece of
marine ply to one atm. Is the cellular
>structure of the wood
irreversibly compressed creating a permanent change
>in density and
therefore buoyancy?
>
>
Thanks
>
> Joe
>
>
>
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