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Re: [PSUBS-MAILIST] RE: payload
Hi Ray,
When the oil is inside the 1 atm sub you have the weight of the oil contributing to the weight of the other objects inside the sub. When you pump that oil outside the sub into a bladder it will rise to the top of the tank and be buoyant. Inside the pressure hull the oil can only effect the sub by its weight but outside it will cause a net increase in buoyancy, however small.
The displacment is a fucntion of the density of the material you are talking about.
I see the advantage of using a non compressible material for adjusting buoyancy, that way you don't have to keep re-adjusting the amount of air. Thats why using a hard ballast tank solves that problem.
Brian
----- Original Message -----
From: "Ray Keefer" <psubs2001@yahoo.com>
To: <personal_submersibles@psubs.org>
Sent: Tuesday, December 05, 2006 17:36
Subject: Re: [PSUBS-MAILIST] RE: payload
> Hi Brian,
>
> --- Brian Cox <ojaivalleybeefarm@dslextreme.com>
> wrote:
>
> > Hi Ray,
> > You would still be losing the weight
> > of the oil from inside the sub.
>
> From inside the sub you would loose weight, however
> you gain weight outside the sub, with a net gain/loss
> of zero. The weight stays the same.
>
> > And you would
> > realize positive buoyancy from the oil ( in a
> > badder) in a open tank connected to the sub.
>
> Not for the lighter density of the oil. For the more
> volume the total displacement of the sub (hull +
> bladder).
>
> > You
> > would have to use way more oil than you would just
> > using air.
>
> The problem with air is that it is compressable. You
> will need more air to fill a bladder at a deeper depth
> then at a shallower one. As you change depths the
> volume of the bladder would have to be adjusted.
>
> Oil would not be compressable. Fill the bladder to the
> volume you want and close a valve to trap that volume
> in the bladder. No matter what depth you are in the
> volume will stay consistant.
>
> Regards,
> Ray
>
>
> > I'm not sure I am comprehending the
> > though on this.
> >
> > Brian
> >
> > ----- Original Message -----
> > From: "Ray Keefer" <psubs2001@yahoo.com>
> > To: <personal_submersibles@psubs.org>
> > Sent: Tuesday, December 05, 2006 11:15
> > Subject: Re: [PSUBS-MAILIST] RE: payload
> >
> >
> > > Hi Brian,
> > >
> > > I think the idea is to change the amount of
> > > displacement instead of changing the amount of
> > weight.
> > > Pump the oil into the bladder and more water is
> > > displaced with the same weight of sub. Making the
> > sub
> > > more bouyant. Pump the water out of the bladder,
> > > bladder collaspes causing less displacement for
> > the
> > > weight, causing the sub to become less bouyant.
> > >
> > > Regards,
> > > Ray
> > >
> > > --- Brian Cox <ojaivalleybeefarm@dslextreme.com>
> > > wrote:
> > >
> > > > Water would be heavyer
> > > >
> > > > Brian
> > > >
> > > > ----- Original Message -----
> > > > From: "Andy Jensen" <drewacard@charter.net>
> > > > To: <personal_submersibles@psubs.org>
> > > > Cc: <ShellyDalg@aol.com>
> > > > Sent: Tuesday, December 05, 2006 07:37
> > > > Subject: Re: [PSUBS-MAILIST] RE: payload
> > > >
> > > >
> > > > > I was thinking about using an oil kept in side
> > the
> > > > sub and pumping it into an expandable bladder
> > out
> > > > side the sub using either an electric or hand
> > > > hydraulic pump.
> > > > >
> > > > > one through hull and one valve. A truck inner
> > tube
> > > > in a small thin tank open tank.
> > > > > using water to force the oil back in. Most
> > > > hydraulic connections are rated at 3000PSI
> > working
> > > > pressure should give me plenty of over head for
> > > > 600'.
> > > > >
> > > > > It seems to simple so what am I missing?
> > > > >
> > > > > Andy J.
> > > > >
> > > > >
> > > > >
> > > > > ---- ShellyDalg@aol.com wrote:
> > > > > Kory. I have always thought trim tanks were to
> > > > adjust trim, not compensate
> > > > > for varying loads.
> > > > > Water density changes with temperature and
> > > > salinity, but not very much. It
> > > > > is possible to run into a salty current or
> > water
> > > > layer and trim can be added or
> > > > > reduced to compensate.
> > > > > Sometimes subs have forward and aft trim tanks
> > to
> > > > change the angle of the
> > > > > sub while still maintaining neutral buoyancy.
> > > > > Adding lead ballast before a dive, depending
> > on
> > > > load, is easier than having
> > > > > a separate, large system with associated
> > piping
> > > > and tanks which requires
> > > > > maintenance, cost, and monitoring.
> > > > > With a few dives, you know how much added
> > weight
> > > > your sub needs to reach
> > > > > neutral, and then you adjust with weights from
> > > > there for added passengers,
> > > > > cargo, new equipment, or whatever.
> > > > > Trim tanks need to be at one atmosphere,
> > whether
> > > > full or empty.
> > > > > Ballast tanks are ambient.
> > > > > If your trim tank is half full and open to the
> > > > sea, ( like a ballast tank )
> > > > > the air will compress when you get deeper, and
> > > > you'll start sinking fast.
> > > > > Large, one atmosphere tanks for trim will
> > require
> > > > heavy walled tanks, fill
> > > > > valves, drain valves, pressure monitoring, and
> > > > take up room and add weight
> > > > > because they're thick steel.
> > > > > And you have to flush them out after every
> > dive so
> > > > they don't corrode.
> > > > > Better to have small tanks for trim and carry
> > some
> > > > lead.
> > > > > Just my opinion....Frank D.
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > >
> >
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