RE: Mathematics for sub desginers (beginners)

[Paul Julius <elbereth@pobox.com>]

>From http://www.aquaholic.com/gasses/archem.htm

For example, a cubic foot of fresh water weighs
approximately 62.4 lbs, while a cubic foot of salt water weighs approximately 64 lbs. The extra weight is because
of the dissolved minerals in salt water.

-----Original Message-----
From:	Bear Woods 
Sent:	Thursday, February 18, 1999 2:46 PM
To:	personal_submersibles@psubs.org
Subject:	RE: Mathematics for sub desginers (beginners)

Good explanation.....but I have been operating under the assumption
that seawater is slightly less dense than fresh water.  From the SCUBA
days ~33ft=1atm=14.7psi in sea water, ~30ft=1atm=14.7psi in fresh
water.  In the units below this means ~0.445psi/ft for seawater and
0.49psi/ft for fresh water.  This means that given equal conditions,
the sub in fresh water is more bouyant than the one in sea water.  




---"Morrisson, Richard D" <Richard.Morrisson@PSS.Boeing.com> wrote:
>
> For water pressure at depth consider a box 1' by 1' by whatever
tall.  The area on top of the box is therefore one square foot.  Water
(sea) weighs about 64 pounds per cubic foot (fresh is about 62.4). 
The top of the box must support the weight of (pressure due to) the
water above it.  This weight is 64 times the depth in feet (the pounds
per cubic foot times the height in feet).  Divide the resulting pounds
per square foot by 144 to get psi.  It comes out to about .44psi per
foot.   Hopefully you can follow the logic to this explanation and see
the basis for the formula, which is generally more valuable than the
formula itself.
> 
> > ----------
> > From: 	sebastian.hunt@virgin.net[SMTP:sebastian.hunt@virgin.net]
on behalf of Seb[SMTP:sebastian.hunt@virgin.net]
> > Sent: 	Thursday, February 18, 1999 8:15 AM
> > To: 	'personal_submersibles@psubs.org'
> > Subject: 	Mathematics for sub desginers (beginners)
> > 
> > Hi. Can anyone tell me where I can find out the formulas that are
important for submarine design? Starting quite simple, I still can't
find the formula for water pressure at depth. I assume this would be
elementary physics, but I must have missed that day at school! What
about calculating thrust from a prop, given its dimensions/pitch/speed
etc? My web searches have revealed nothing so far.
> > 
> > I'm also quite keen to track down information about human
tolerances to variations in air pressure and gas mixtures and anything
else that might pose a physical threat to a sub pilot.
> > 
> > Hope someone can point me in the right direction.
> > 
> > Cheers,
> > 
> > Seb Hunt
> > 
> 

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