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----- Original Message -----
Sent: Thursday, November 10, 2005 6:33
AM
Subject: Re: [PSUBS-MAILIST] Forces of
Nature
True If the tank/ cabin is open to the water and no further is
added to keep
the same displacement and keep the air at ambient
pressure.
A point ive never really considered though is that say you
have a dry
ambient design obviously air is being added to keep the inside
of the cabin
slightly above or at ambient pressure and since its dry also
at the same
displacement. however since you are increasing the pressure
therefore
density of the gas inside the cabin this would surely affect the
overall
weight slightly, much in the way a full steel scuba tank starts as
negatively bouyant but as it is emptied throughout a dive
progressively
becomes more nuetrally bouyant as the gas inside becomes
less dense.
however since the pressure inside an ambient design is very
unlikely be very
great ( unless your a loon building a saturation bell) do
you think that any
weight/bouancy change would be significant considering
also that whilst you
are increasing the density oa gas inside the cabin
you are also decreasing
the density of gas inside the supply
tanks.
whoops i think ive just answered my own question and in fact
overall i guess
the whole system will just become slightly more bouyant
due to the loss of
exhaust gasses.
Let me know if you think that
sounds about right,
Cheers,
Dan
>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 19:57:46
-0500
>
>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 -----
> From: Daniel
Edwards
> To: personal_submersibles@psubs.org
>
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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