Brent,
Depends on what depth you are at: 1 cf of ambient air at 132 fsw
equals 5 cf at the surface while at 297 fsw that 1 cf of air ambient equals 10
cf on the surface.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
As scarce as the truth is, the supply has always been in excess of
the demand.
-Josh Billings
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent
Hartwig
Sent: Thursday, December 11, 2008 5:32 PM
To: PSUBSorg
Subject: RE: [PSUBS-MAILIST] MBT Venting Options
Hello Jay,
From time to time I
hear guys mention how large MBT's must use up a lot of air as Frank just
mentioned. But I always thought it wouldn't be a big deal if they blow them
near the surface as you mentioned. Since I've been thinking about large MBT's
on my live aboard sub design, I have been thinking about it. Also if they
just added a small amount of air at depth, just enough to get them moving
towards the surface, that air would keep expanding, and accelerating the sub to
the surface. So when they arrive at the surface the MBT's would be partly or
completely filled and if to much air was added much of it would bubble out the
bottom of the tanks. I would think it would use the same amount of compressed
air per cubic foot of air that is in the tanks when they are at the
surface. Of course there is the disadvantage of the the free
surface affect in the MBT's if they are not divided up enough, and a accent you
can't stop unless you vent.
Regards,
Szybowski
From: bottomgun@mindspring.com
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] MBT Venting Options
Date: Thu, 11 Dec 2008 07:37:05 -0500
As Vance has noted, mushroom valves provide a clean hull solution
for venting the MBTs. Note that on larger subs a cover flange is bolted
over the mushroom vent valve when on the surface for extended periods of time
(i.e. at anchor or at the pier) to protect against air leaks past the valve or
an inadvertent venting of the tank thus preventing an unintended sinking of the
sub. While submerged, the vent valves are left open to vent off any air
that might be leaking from the blow line thus preventing unwanted changes in
buoyancy while submerged. When submariners speak of “riding the
bubble”, they are referring to the air in the hard trim tank as the MBTs
are left completely flooded while submerged. Due to free surface effect and the
larger size of the MBTs, rapid adverse changes to trim can occur if an attempt
made to use the MBTs for trim control. To conserve of HP air for blowing
the tanks, the sub is driven to the surface and the MBTs blown while at or near
the surface. The Kingston valves at the bottom of the MBTs may also be
closed when on the surface for extended periods.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
As scarce as the truth is, the supply has always been in excess of
the demand.
-Josh Billings
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent
Hartwig
Sent: Thursday, December 11, 2008 4:49 AM
To: PSUBSorg
Subject: [PSUBS-MAILIST] MBT Venting Options
Dan and Vance,
I like your idea much
better then what I currently have Dan. Some time I hope to see Vance's
supper secret mushroom vent design. ;)' You guys got me to thinking
and I think I might have a even better option that has some elements of both
your guys ideas. A remote valve would need to be externally mounted above
the highest point on the tanks in order to vent all the air. A large valve
would stick out like a sore thumb or odd hood ornament. Then I would have
two rods going down at an angle with a small pair of U joints at each end,
unless I use two pairs of bevel gears near the conning tower and a short
vertical rod between them.
So what I was thinking
was to have a piston type valve inside the top area of the MBT's with a 2 to 3
inch opening with a spring around the rod that protrudes vertically below
the piston head that has one or more soft O-rings mounted on it. Then to that
I'll attach a horizontal arm to the bottom of the vertical rod, which is
operated at the other end by a horizontal rod that goes through the pressure hull
heads. Then for the front MBT, the rod that is now inside the hull would
have a small pair of bevel gears attached to it so you can go towards the port
side of the hull. Once at the port side of the hull you have one more pair of
bevel gears added so you can run a rod up to the pilot. This way you can
have a low profile valve that when you turn the lever to open it, you have to
hold it there for a few moments until the tanks have vented, then when you let
go they spring shut. I saw a mini version of this piston valve on two
inflatable pontoon fishing boats that I needed to let the air out of today.
Another option to
operate this type of valve, is to not use the internal actuating assembly I
just mentioned, and instead use a pair of Habonim pneumatic valves just inside
the heads. One in front and one in the aft. I've found them more commonly
on ebay of late at very reasonable prices, from $50 to $150 each. I
prefer the Compact 4's but the Compact II's are nice as well.
http://shop.ebay.com/items/?_nkw=habonim&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=hamonim&_osacat=0
Regards,
Szybowski
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] K-250 #118 In Action
Date: Wed, 10 Dec 2008 09:31:22 -0500
From: vbra676539@aol.com
Brent and Dan,
I converted mine to George's reach rod assembly. It works very well, of course,
but was a pain in the A to do initially. To tell the truth, I'm not sure I
would do it again. You still end up with tubing running from the fairwater
tanks. Dan's suggestion of a valve on each tank is better. And use a BIG valve,
an inch at the minimum. Waiting for the MBTs to vent is torturous through little
tubing. My new ones, pneumatic mushrooms for lack of a better term, will be two
inch clear opening. That's about the size on most of the old Hyco boats, and
those boys dive quick when the time comes. Having spent a lot of time waiting
as the sub wallows around trying to vent, I can tell you with certainty that
faster is better.
Vance
-----Original Message-----
From: Dan H. <Jumachine@comcast.net>
To: personal_submersibles@psubs.org
Sent: Wed, 10 Dec 2008 7:46 am
Subject: Re: [PSUBS-MAILIST] K-250 #118 In Action
If
I were you I think I would consider filling all the little holes and using the
big holes for a standard rotating through hull with linkage to valves
mounted directly on top of the MBT's. Or maybe plug all the holes and
relocate new through hulls for the same purpose. That way you can
eliminate the need for plumbing to the valves and the through hull / valve
combination. The over all design may not look as clean but you can solve
your valve and corrosion problems and they would vent much
better also. I know if I had mine to do it over again, I
would have done it that way.
-----
Original Message -----
Sent: Tuesday, December
09, 2008 2:46 PM
Subject: RE: [PSUBS-MAILIST]
K-250 #118 In Action
Dan,
I don't see any thing
like that. It does have a standard snorkel, and you can see if you
look carefully the downward turned float part of the snorkel. I also
thought it might be an extension of the snorkel but the picture shows the
snorkel float as it was when I got it.
Here are the pictures
of the conning tower parts being removed.
I
really don't like the multi-hole mounting design used for these valves. Dan
isn't yours a single hole configuration that you turned some parts for
it? Also the exterior top area of the valves holds some water, so that
area got some heavy rust pitting I'll have to weld in.
From: Jumachine@comcast.net
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] K-250 #118 In Action
Date: Tue, 9 Dec 2008 08:53:40 -0500
Not
much of an idea Brent.
It
doesn't happen to have part of a 1950 Chevy pickup rear view mirror still stuck
to it, does it?
That's
the only thing I can think of.
Do
you have a snorkel on it? Most of the K-subs have one but it should be
closer the conning tower, unless they added a piece of tubing.
-----
Original Message -----
Sent: Tuesday, December
09, 2008 3:06 AM
Subject: [PSUBS-MAILIST]
K-250 #118 In Action
I had a couple of pictures that came
with my subs documentation thats some of you have not seen. I don't know what
the little rod coming out in front of the dome is for.
http://cid-5085d10eb6afe47c.skydrive.live.com/browse.aspx/K-250%20%7C3118%20in%20Action
Regards,
Szybowski
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