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

To: <personal_submersibles@psubs.org>
Subject: Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT) knowledge)
From: "Dan H." <jmachine@adelphia.net>
Date: Thu, 6 May 2004 18:53:14 -0400
References: <BAY7-F89yfgmiCFzwKH000056b9@hotmail.com>
Reply-to: personal_submersibles@psubs.org
Sender: owner-personal_submersibles@psubs.org
Pierre,

Sorry I was vague with my question/statement about MBT / VBT.

You mentioned in a former posting that you intended on keeping some reserve
air in your MBT.   ( If I understood you correctly.)  Your Main Ballast Tank
is what you use to increase freeboard, when surfaced.  It's typically a tank
that can't contain much pressure and the bottom of it is opened to sea
water.  When you blow air in, the water is pushed out the bottom.  It's
referred to as a "soft tank."

A VBT, Variable Ballast Tank, is a true pressure vestal and referred to as a
"hard tank."  It has valves to control the air in and out and the water in
and out.  It's used to set the buoyancy of the sub for diving then closed
off.  A VBT may be filled to any capacity that is required to trim the sub.

A MBT is either fills with air when on the surface to create as much
freeboard as possible, or TOTALLY full of water when diving.

If you have air in the MBT when your diving it will compress as you go
deeper and your sub gets heavier the deeper you go.  A drastic situation.
Remember the MBT has no valve to sea water and isn't a pressure vestal
capable of holding more then a few PSI even if you did install a valve.

I'm not totally familiar with your ambient design.  This is the way it would
work in a 1 atmosphere sub.  I think you would have something similar.
Correct?
Did I clear up my statement or just muddy up the water even more?  ;-)

Dan H.





----- Original Message -----
From: "Pierre Poulin" <pipo305@hotmail.com>
To: <personal_submersibles@psubs.org>
Sent: Thursday, May 06, 2004 8:30 AM
Subject: Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT) knowledge)


> Hi Dan!
>
> Hum... I can't?
>
> Are you talking about free-surface inside the ballasts?
>
> I don't understand what you mean... sorry.
>
> Pierre "scratch his head" Poulin
>
>
>
> >From: "Dan H." <jmachine@adelphia.net>
> >Reply-To: personal_submersibles@psubs.org
> >To: <personal_submersibles@psubs.org>
> >Subject: Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT)
> >knowledge)
> >Date: Wed, 5 May 2004 20:01:08 -0400
> >
> >Pierre,
> >
> >So then your soft tanks aren't really soft are they?  You realize that
you
> >can't keep air in soft tanks and control your dive right?
> >
> >Dan H.
> >----- Original Message -----
> >From: "Pierre Poulin" <pipo305@hotmail.com>
> >To: <personal_submersibles@psubs.org>
> >Sent: Wednesday, May 05, 2004 10:39 AM
> >Subject: Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT)
> >knowledge)
> >
> >
> > > Thanks Dan!
> > >
> > > So basicaly it's very similar to a soft tank but with a valve at the
> >bottom
> > > (drain). My soft tanks are already configured that way but for another
> > > reason (so I can keep some pressurized air inside the tanks if I need
it
> >to
> > > resurface if I run out of air...) but I think I might built a VBT and
> >use
> > > electric/pneumatic valves so it could be easy to adjust the bouyancy
> >with
> > > small push from button... And also, it might be a good idea to always
> >have
> > > the VBT at ambient pressure. It could be easyer to adjust.
> > >
> > > As for the hatch seal, I must confess that my hatch is not as flat as
I
> > > would it to be... I discovered that when welding, things tend to bent
> >every
> > > direction they want! And the hatch as a complex shape. Also, The
"flat"
> >area
> > > is a square tubing of 0.125" thick wall... Not sure I can groove it.
But
> > > thanks anyway! It is not that big a problem for me...
> > >
> > > Pierre "VBT man" Poulin
> > >
> > >
> > >
> > >
> > > >From: "Dan H." <jmachine@adelphia.net>
> > > >Reply-To: personal_submersibles@psubs.org
> > > >To: <personal_submersibles@psubs.org>
> > > >Subject: Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT)
> > > >knowledge)
> > > >Date: Wed, 5 May 2004 08:24:37 -0400
> > > >
> > > >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 !
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> > > > >
> > > > >
> > > > >
> > > > >
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References:
- Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT) knowledge)
  - From: "Pierre Poulin" <pipo305@hotmail.com>
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