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RE: Mathematics for sub desginers (beginners)
I don't know where you got the information that seawater is less dense but I think you should re-check it! The rule of thumb I remember is 34' not 30' for freshwater. Consider that seawater is just regular water with a bunch of rock (salt) dissolved in it, which makes it heavier for a given volume.
> ----------
> From: Bear Woods[SMTP:bearasaur@yahoo.com]
> Sent: Thursday, February 18, 1999 12:45 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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