Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT) knowledge)

["Dan H." <jmachine@adelphia.net>]

Brian,

Your ballast tanks need to vent upward, so as long as you don't run your
lined up and back down ward again, you should be all right no matter where
your valves are.  Don't create a condition where water can get trapped in
your vent lines.

If you run a pipe through the hull and locate the valve inside, you actually
need three valves.  The one that your using to control with and two on the
inside where each thru hull comes in and out as a safety.  With the valve
outside the hull you can put two O-rings on the shaft, one to seal and the
extra one for safety.   In that way, it's simpler to put the valves on the
outside.

But putting the valves on the inside, you can place them where it's
convenient to operate them from the operators seat with out complicated
linkages to external mounted valves.  Also they are protected better inside
the hull.  The K-boat has three on the outside and a bunch on the inside.
It depends on what works for you.

I don't see a lot of need to control the valves from outside of the hull.
To make an unmanned dives for testing what you do is trim the ballast to
near neutral and then weight the sub to slightly negative and let it
submerge to your test depth on a line.  It only has to weigh a few pounds on
the line to descend.  If your test goes well, you can pull it up hand over
hand.  If your test goes bad.  Well........ You won't be using your hands to
pull it up, they'll be busy wiping tears.  :-(

Dan H.

----- Original Message -----
From: "Brian Cox" <ojaibees@ojai.net>
To: <personal_submersibles@psubs.org>
Sent: Wednesday, May 05, 2004 10:49 AM
Subject: Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT) knowledge)


> Dan,  I didn't ask the question.  But anyway I was planning on controlling
my ballast with thru hull shafts that turn the valves which are located
outside the pressure hull.  I have notice that some people bring the actual
air lines in and out of the pressure hull.   The reason I am locating them
out side is so they could be controlled outside if need be.  Does anyone
know of any down side to doing this ?
>
> Brian
>
> ----- Original Message -----
> From: "Dan H." <jmachine@adelphia.net>
> To: <personal_submersibles@psubs.org>
> Sent: Wednesday, May 05, 2004 5:24 AM
> Subject: Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT)
knowledge)
>
>
> > Brian,
> >
> > The VBT has two connections attached to it.  One is a one inch pipe that
> > water moves through and the other is a half inch pipe that air moves
> > through.
> >
> > The water port is located at the rear of the tank (not important) and
has an
> > internal elbow and pipe that goes to the bottom of the tank, so when
> > reducing ballast, it drains clear to the bottom.  The smaller line in
> > located at the top of the tank so when reducing pressure, it vents out
air.
> >
> > The water port has a one inch ball valve attached to it after it exits
the
> > tank.  This is controlled from the pilots seat through linkages that
pass
> > through a thruhull fitting.
> >
> > The air port is plumbed directly into the sub and then to two valves
near
> > the pilot seat.  One of these valves allows you to blow air into the
ballast
> > tank to pressurize it.  The other valve is a vent valve that connect to
a
> > vent thruhull in the top of the hull. This valve allows you to bleed off
> > pressurizes air from the MBT to allow water to enter the water port.  To
> > allow water to fill the MBT properly, this venting system must be
located
> > above the top of the MBT.  My vent is located just forward of the
conning
> > tower in the hull.  An added advantage is that you can see the air
venting
> > through a viewport.
> >
> > To decrease buoyancy:  (go down)
> > Open the vent valve.
> > Open the water valve.
> > When neutral buoyancy is reached close off both valves and power down
with
> > the thrusters.  ( Of course if you go to negative buoyant, you can just
sink
> > downward.)
> >
> > To increase buoyancy:  (come up)
> > Open the air pressure valve to charge the VBT above ambient pressure.
> > Open the water valve.
> > When you hear air blowing out the water port, the tank is empty and you
can
> > close all valves.  (If making a miner adjustment to the positive,
pressurize
> > and then just crack the water valve a bit until you reach the desired
> > buoyancy.)
> >
> > I hope this helps!
> >
> > Pierre,  Your hatch seal really isn't a difficult problem.  There is no
need
> > to reinvent the wheel!  O-rings exist and they are perfect for your
needs.
> > A standard Buna O-ring, with a cross section of around .200 inch or
more, in
> > a groove within two flat matting surfaces is all you need.  Your "hatch
hold
> > downs" will apply all the force you need to compress the O-ring if your
> > mating surfaces are flat.  A 24 inch Buna O-ring is about $10.  Cheep,
off
> > the shelf and easy to replace anywhere if needed.
> >
> > Keep It Simple, Dan H.
> >
> > ----- Original Message -----
> > From: "Pierre Poulin" <pipo305@hotmail.com>
> > To: <personal_submersibles@psubs.org>
> > Sent: Tuesday, May 04, 2004 9:49 PM
> > Subject: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT) knowledge)
> >
> >
> > > Hi Dan!
> > >
> > > I know that there is a Variable Ballast Tank in a K-350. And I imagine
> > that
> > > yours have one too.
> > >
> > > Could you please tell me how this VBT is connected? Valves, vents,
> > drains...
> > > I was planning to have a pneumatic cylinder and a piston to adjust
> > buoyancy
> > > using readyly availible ambient pressure but maybe a VBT is easyer to
> > built
> > > and could do the same job.
> > >
> > > I was thinking that we could use some pneumatic push button valves for
> > ease
> > > operation...
> > >
> > > Thank you very much!
> > >
> > > Pierre Poulin
> > >
> > > _________________________________________________________________
> > > MSN Messenger : discutez en direct avec vos amis !
> > > http://messenger.fr.msn.ca/
> > >
> > >
> > >
> > >
> > >
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