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
************************************************************************
************************************************************************
************************************************************************
The personal submersibles mailing list complies with the US Federal
CAN-SPAM Act of 2003. Your email address appears in our database because
either you, or someone you know, requested you receive messages from our
organization. If you want to be removed from this mailing list simply click
on the link below or send a blank email message to:
removeme-personal_submersibles@psubs.org Removal of your email address from
this mailing list occurs by an automated process and should be complete
within five minutes of our server receiving your request. PSUBS.ORG PO Box
311 Weare, NH 03281 603-529-1100
************************************************************************
************************************************************************
************************************************************************