----- Original Message -----
Sent: Thursday, November 17, 2005 10:13
PM
Subject: Re: Re: [PSUBS-MAILIST] Re:
Variable Ballast Calculations, Bill
Regardless, you still need compressed air to blow
the tanks. Exterior main ballast tanks really only need to be blown near
the surface, where the pressure is less (unless you need some kind of
emergency blow). Just enough to keep you afloat/sink. It's always
smarter to have a pressure tank instead of going "direct". The main ship
compressor simply maintains say a 3000 psi level at all times, either from
surface air or bladder air. All other ballast tanks are blown from
here. Military subs go up and down in this way I'm sure as it doesnt
give off any bubbles, and they raise/lower depth an unlimited amount of time;
simply recycling the air they have.
Figure, you can hold a closet-full of air inside
a small scuba tank. That's plenty. Of course, the initial main
ballast vent would be to the atmosphere since it'd probably take FOREVER to
compress them into a tank. Being able to get the air back
into the sub just seems like an extra layer of flexibility, albeit unnecessary
since you can just use the outside air - hehe. That main vent would simply be
a one-way valve to keep the water out of the bladder btw.
As for the rest of the smaller ballast/trim tanks
they could more easily/quickly be compressed back into the main compressor
tank.
I guess you could say if you had a ballast/trim
system that really only employed a few tanks it'd be beneficial to use a
bladder as u could use it at depth to raise/lower depth without wasting air or
having to build a bulky ballast tank. The positive pressure outside the
bladder aids in getting the air back into the main compressor
tanks.
Anyways, just thoughts. Those kevlar
pressure bags are very expensive. But it limits component exposure
to the elements and cuts down on airspace. Only really pays if you're
building the "ultimate sub" and mostly is beneficial for consumable and
waste tanks. Using them for ballast tanks just cuts down on
the steel I guess. Still fun to dream though.
:)
All in all, composites are the future for
sub-building. We all know this. Fun to think of ways to apply the
technology.
SH
p.s.
btw, I looked up a few compressors. The
ones fire departments use can do like 20 cubit feet/minute at 6,000 psi.
Obviously much faster at lower pressures. Of course, then you have to
factor in the total airspace added from using a large compressor to begin
with. Would simply using more TANKS be better?? UGH! too
much to think about.