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I am approaching your 3 tons weight also. I have a K350 pressure
hull etc but have extended
it out to a 20' length. I am using the stock 350 front glass MBT
and have enlarged the rear
MBT. I am also building saddle tanks for the sides. At this time I
have no plans on putting in
a VBT system. I agree with Vance on just riding a bubble. For
my sub going a little negative
buoyancy will serve my purposes. I will be able to load
the
tanks individually for any correction needed.
I have a 6' battery pod between to 10' pods. The center one will
be able to slide
fore and aft for trim. Lead moved around by hand on the interior
for fine tuning.
Dean
In a message dated 2/5/2009 10:20:32 A.M. Central Standard Time,
ojaivalleybeefarm@dslextreme.com writes:
My
pressure hull is small but my soft ballast is hugh ! My ballast
structure is going to come in at around 3 tons ( on land wieght) .
I have an area where everything has to go, so I can't just add stuff onto the
outside. ( and I keep thinking of more things to add !! ( cranes,
anchors, manip arms etc..) ) Sounds like not a good idea to
put VBT inside. I may do a sliding lead weight on a rail on
the keel for trim .
Brian
Let me qualify that.
Assuming stable depth and minor quantities of air, the sub will do what you
want it to do, but slowly. There is some finesse to it, of course. However,
a PC12, for instance, weighs approximately 8 tons, and a squirt of air might
be just a few pounds difference in its trim. It WILL make a difference, just
not a massive one (unless you want it to). That same squirt of air in a 3300
pound K-350 will make a much more immediate difference, with longer lasting
effects. In other words, caution is advised, as the Captain's finest will
respond MUCH faster than the PC12, simply because it weighs so much
less.
That said, I'm not advocating you toss out your trim system. My
question was aimed more at design. A 32" pressure hull is SMALL. So why
stick a spherical tank into such a small space, unless it can be made to
serve some other purpose. For instance, the DW2000s are built to sit in, so
the internal soft tank is under the seat. In other words, it isn't in
the way.
Vance
-----Original Message-----
From:
vbra676539@aol.com
To: personal_submersibles@psubs.org
Sent: Thu, 5
Feb 2009 9:31 am
Subject: Re: [PSUBS-MAILIST] hard ballast
Pretty
much. V -----Original Message----- From: Brian Cox < ojaivalleybeefarm@dslextreme.com> To:
personal_submersibles@psubs.orgSent:
Thu, 5 Feb 2009 6:57 am Subject: RE: [PSUBS-MAILIST] hard ballast
So
you're saying that the mass of the boat is is so much that the change in the
amount of air in the soft ballast takes a long time to affect the buoyancy
? Except it's more pronounced in shallow water.
Brian
Simply put, there is
enough mass there to work without a vbt system, so why bother.
What
difference does the space make outside the
boat?
V
-----Original Message-----
From: Brian Cox
<ojaivalleybeefarm@dslextreme.com>
To:
personal_submersibles@psubs.org
Sent:
Wed, 4 Feb 2009 8:02 pm
Subject: RE: [PSUBS-MAILIST] hard
ballast
The reason I'm contemplating it is to save space. It would be
a sphere and if I put it outside in front of my 32" dia pressure hull then
I will have the end cap of the pressure hull butting up against the hard
ballast sphere so there would be this area where the two spheres come
together that would be wasted.
Vance, Does the Aquarius not have hard ballast
tanks? Sorry if you already be thru this.
Brian
They probably did
not replace the VBT. You just dive a little heavy and ride the bubble.
There has been lots of talk here about that, but I'm here to tell you,
it works just fine. Aquarius hasn't had a trim system since about 1975,
and is working its little buns off all year, every year. You trim the
boat carefully during pre-dive, and then you don't need much extra
buoyancy. The real issue is in shallow water where that bubble can and
does expand rapidly. But if you think about nearly any partially
flooded ambient sub on the planet, guess what it uses as primary
buoyancy. A bubble. It works just fine. Trust
me.
Vance
-----Original Message-----
From: Brent
Hartwig <brenthartwig@hotmail.com>
To:
PSUBSorg <personal_submersibles@psubs.org>
Sent:
Wed, 4 Feb 2009 6:01 pm
Subject: RE: [PSUBS-MAILIST] hard
ballast
Brian, I
meant to say the K-250 boats generally have short VBT just under the
pilots seat, inside. But some like the Great White K-250 have
removed them so they can have two people inside. I still don't
know exactly what they replaced it with. I'll have to ask Greg
Cottrell, or Scott Cassell.
Szybowski
From: brenthartwig@hotmail.comTo:
personal_submersibles@psubs.orgSubject:
RE: [PSUBS-MAILIST] hard ballast Date: Wed, 4 Feb 2009 15:52:29
-0800
Hi Brian, The K boats generally have a short VBT just under
the pilots seat. You might also consider using a bladder type that you
can let water into with a valve, and then either just dump it out when
at the surface, or better yet have a high pressure electric pump that
can empty it for you at depth. Another version of this is a box
tank, like was used in the S101 that you operate just like the bladder
with a pump. The box tank can not take internal or external pressure, it
is just a holding tank. Here is a drawing of the S101. The
holding tank is just behind the conning tower, and taking up the lower
half of the hull.
http://www.msubs.com/Images/S101%20Images/S101%20-%206.jpg
Szybowski
From: ojaivalleybeefarm@dslextreme.comTo:
personal_submersibles@psubs.orgSubject:
[PSUBS-MAILIST] hard ballast Date: Wed, 4 Feb 2009 14:43:01
-0800
Hi All,
I'm contemplating puting a hard ballast tank inside my pressure
hull. Do any of the Kittridge subs have this same set up ?
Brian
=
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