What if one connected a check valve in a pipe near the boats
hull (with the flow aimed outward) and used a hand operated piston pump with
long enough handle to apply enough force on a short stroke thin diameter
piston to expell water against outside sea pressure while at depth to reduce
the amount of water contained in this tank? When the handle is again drawn
back, additional water from this tank could enter this piston. Once
finished, isolation valves could be closed to prevent additional water from
transfering.
&nb
sp; David Bartsch
> Date: Tue,
21 Jul 2009 23:09:04 -0700
> From:
cast55@telus.net> To:
personal_submersibles@psubs.org>
Subject: Re: [PSUBS-MAILIST] water level
>
> Don't forget to
account for the possibility of having to adjust=2 0in the
> other
direction - i.e. adding buoyancy to compensate for reduction in
>
volume as the hull deflects at depth. For a small, shallow sub, this
> won't be significant, but as depth and the size of vehicle
increase, the
> change in volume may become significant.
>
> -Sean
>
>
>
ShellyDalg@aol.com wrote:
> >
Hi David. A sight glass is the easiest to read on a tank, but it's not
> > much use to us for variable ballast tanks. The reason being,
it would
> > need to be able to withstand a lot of pressure and
they are hard to
> > keep clean.
> > The variable ballast
tank, often called "hard ballast tanks" are
> > pressure vessels
that will withstand being opened at depth to adjust
> > buoyancy
when you're at your deepest operating depth, plus what ever
> >
safety factor you wanted.
> > Although a simple "trim tank" can be
used to adjust buoyancy at
> > or near the surface, and then
valved off with a set amount of water
0A> > ballast in it, no
adjustment can be made when you're deep unless the
> > tank is
able to withstand the pressure at your deepest dive.
> > Once you
open a hard ballast tank at depth, and close the valves
> > to
maintain that level of water, the pressure is "locked" into that
>
> tank. Then, when you g et back to the surface, you release that
> > pressure by opening the valve and letting the pressurized
bubble blow
> > out the tank.
> > If you want to adjust
for more buoyancy at depth, due to changes
> > in salinity or
maybe you picked up something from the bottom, you must
> > blow
high pressure air into the tank until the correct water volume is
>
> achieved, then close the tank off to maintain that level of
water.
> > Knowing just how much water is in your hard ballast tank
is a
> > problem.and one that I considered a while back. The
"sight glass"
> > method would require a very heavy walled clear
tube with valves in
> > case it developed a leak. I'm not sure how
risky that would be if it
> > blew out but it should be fairly
easy to build.
> > Another method would be to use a "see
through"tank. There's a
> > filament wound fiberglass/composite
tank available called "Lite"
> > propane tanks and they come in a
few sizes, the largest being about 8
> > gallons for use on
warehouse type propane fork lifts. These will
> > withstand 250
psi ( with a safety factor) and you can tell at a glance
> > how
much liquid is in it. They come with threaded fittings molded in,
>
> and a metal "basket" that protects it from bumps. They run about $300
> > each I think.
> >=2 0I'm leaning toward the see
through tank right now, and have a
> > place inside designed for
it. That only gives me 64 pounds of variable
> > ballast though. (
8 gallons at 8 pounds per). It would be nice to
> > have more
adjustment, like if you found something and wanted to pick
> > it
up and bring it back to the surface. It's possible to blow a little
>
> air into the "soft" ballast tank for lifting purposes, but that bubble
> > will become much larger as you near the surface, making it
difficult
> > to control buoyancy as your depth changes.
>
> Most psubs have a few lead bricks that get adjusted at the
>
> surface for how much payload you're carrying on any given dive, like
> > an additional passenger, some added machinery or cargo, or
what ever
> > will change the total weight of the sub.
>
> Buoyancy is based on water displacement and total weight in water,
> > so when you add a passenger, you must ask them how much they
weigh and
> > adjust the lead bricks according ly to achieve
"neutral" buoyancy. A
> > hard ballast tank is required for small
changes in buoyancy like
> > salinity and temperature changes. For
instance, if I launch my boat in
> > the harbor, which is a river
mouth with a small amount of dissolved
> > salts, and then motor
out into the ocean where the salini ty level is
> > higher, the
sub is displacing more weight ( the water is saltier so is
> >
heavier ) so additional ballast must be added to maintain "neutral. It
> > runs about 4% from fresh to salt water while temperature can
add about 1%.
> > These are percentages of "displacement" or the
total volume of water
> > displaced by the submarine. Several
"high dollar" subs I've read about
> > have as much as 240 pounds
of "variable" ballast. Not sure how they
> > achieve that, but
it's useful if you plan on bringing back samples or
> > stuff from
down deep.
> > Frank D.
> >
> >
------------------------------------------------------------------------
>
> What's for dinner tonight? Find quick and easy dinner ideas
>
> <
"http://food.aol.com/dinner-tonight?ncid=emlcntusfood00000009>;
for any
> > occasion.
>
>
>
>
>
************************************************************************
>
******************************************
******************************
>
************************************************************************
>
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 53
> Weare, NH 03281
>
603-529-1100
>
************************************************************************
>
************************************************************************
>
************************************************************************
>
Windows Live™ Hotmail®: Celebrate the moment with your favorite sports pics.
Check it out. =