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Re: [PSUBS-MAILIST] Bill Gifford's Project

Steve,

I don't really have answers to your dual hull design.  Granted, a duel hull,
one tank inside another with ribs fused between them would make a strong
design, much like an I beam is stronger then a T beam.  But, the draw backs
of this design for a sub aren't worth it.  I would want to be able to
inspect the hull for corrosion for one thing.  There is nothing that I would
trust to fill the voids with that is sure to keep moisture out and prevent
corrosion.  Nested tanks aren't a good design.

Using a tank end welded to each end of your hull as MBT's is good as long as
you can inspect it from the inside.

Actually there isn't much advantage using a propane tank in the first place.
A used one may have corrosion and it STINKS!  A new one isn't any cheaper
then buying two tank ends and having a sheet of steel rolled for a hull.
You still have to cut a tank apart to put framing inside.  You could frame
it in pieces but it's much easier the keep your hull round if you start our
accurate full circle round frames.  Don't forget, a propane tank will work
just as well for it's intended purpose no matter if it's round or not.  A
PSUB size sub hull should be true round to within a eight of an inch or
closer.

If the reason for using a propane tank is because it looks like most of the
work is already done for you, FORGET IT!!!!
The round tube with two end caps isn't five percent of building a complete
sub.  It's only a small part that you have to cut opened anyway.

My opinion, Dan H.


----- Original Message -----
From: "Steven Mills" <barycenter@earthlink.net>
To: <personal_submersibles@psubs.org>
Sent: Friday, May 23, 2003 11:52 PM
Subject: Re: [PSUBS-MAILIST] Bill Gifford's Project


> >From: Dan H. <JMachine@adelphia.net>
> >
> > I visited Bill's site and read what you quoted.  Bill's project sure
looks
> > interesting but I wish, for confusion sake, Bill would have noted that
his
> > propane tanks that were tested to 325 PSI and rated at 250 PSI for
INTERNAL
> > pressure!  External pressure is a TOTALLY different matter.   I'm sure
Bill
> > realizes this and is designing accordingly.
> >
>
> Thanks.  That thought had occurred to me just before receiving your
> response.
>
> Perhaps I need a little clarification on the definition of dual pressure
> hulls.  Is Bill's design a dual hull or a reinforced single pressure hull
> [ using the small tube and frames for reinforcement ; and the smaller
> tank left open ended after the cut or capped-off]? The ends of the
> smaller tank were cut and welded to the larger for hard ballasts.
> For simplicity, my mind envisions something akin to a thermos bottle;
> 2 closed vessels reinforced with frames or stiffening rings between
> the 2 hulls. [ Which brings me to the next question...]
>
> > One thing to consider when designing one tank nested inside another is
that
> > you can't weld your framing to both tanks unless the difference in size
is
> > great.
>
> So, I would think that the framing would be welded on the outside of the
> inner hull?  The outer hull would not only be subjected to pressures
> initially, but also to temperature differentials?  The contraction and
> expansion over time would fatigue and stress the welds at the inner
> part of the outer hull first if the 2 hulls were welded together at the
frames?
> The temperature in the inner hull would be affected by intenal environment
> ie., body heat and residual mechanical/electrical heat?  Or are these
> minute considerations?
>
> >Even if you design it strong enough without the frames welded to
> > both tanks, you still have the risk of corrosion in places that you
can't
> > access for inspection.
> >
>
> Would a foam, dessicant, or bonded covering [ anodizing the steel?]
> solve this problem?
>
> --Steve
>
>
>
> > Dan H.
> >
> > ---- Original Message -----
> > From: "Steven Mills" <barycenter@earthlink.net>
> > To: <personal_submersibles@psubs.org>
> > Sent: Thursday, May 22, 2003 1:34 PM
> > Subject: Re: [PSUBS-MAILIST] Bill Gifford's Project
> >
> >
> > > >From: Warren Greenway <opensourcesub@yahoo.com>
> > > >
> > > > They are rolled and welded (so, yes, they do have a
> > > > seam.) The ends are then welded onto the tube. This
> > > > is standard practice, and while there may be variation
> > > > you can bank on them being built this way.
> > > >
> > > > Warren.
> > >
> > > Thanks.
> > >
> > > Bill uses 2 tanks with the same ASME rating, but it is a single
> > > pressure hull. [ see quote/specs below ]
> > >
> > > If a double hull were to be designed, would you have the inner hull
> > > at a stronger and thicker spec than the outer hull? [ using 2 propane
> > > tanks ]
> > >
> > > Also, this might seem an oddball question or inconsequential, but
> > > should the weld seams on both hulls be parallel and lined up with
> > > each other?
> > >
> > > --Steve
> > >
> > > ....quoted fromBill Gifford's website....
> > > http://www.giffordmarineinc.com/sub/little_gato5_9_01.htm
> > >
> > > "I have chosen to use two new propane tanks to form the pressure hull.
> > > Each tank is made of A-516 grade 70-pressure vessel steel, .270 inch's
> > > thick. Both tanks were pressure tested to 325 pounds. They have a
working
> > > pressure of 250 pounds and are ASME rated with a spec. Plate on each
> > > tank. I am installing three by one half-inch reinforcement rings every
> > two-foot
> > > on center. Plus additional deck and bulkhead framing. The one-tank
easures
> > > 17.6 ft. long and the other is 9 ft. I have cut a hole in the top of
the
> > larger tank,
> > > around that I intend to install the conning tower, which is made up of
> > parts
> > > of the smaller tank and additional plate. I have cut the ends from the
> > smaller
> > > tank and have connected them on each end of the larger tank for hard
> > > ballast. I have purchased a eighteen-foot by two foot by quarter inch
pipe
> > > for the soft ballast tanks. The pipe was split log ways and will be
> > attached
> > > to each side, to form the side tanks. The sub will have a displacement
of
> > > approx. 18,000 lbs. "
> > >
> > > >
> > > > --- Steven Mills <barycenter@earthlink.net> wrote:
> > > > > I haven't examined a propane tank closely, but are
> > > > > they filament
> > > > > wound and rolled or are the ends welded to the tube?
> > > > > Is the tube
> > > > > seamless or also rolled and welded? Are they all
> > > > > manufactured
> > > > > the same way?
> > > > >
> > > > >
> > > > > --Steve
> > > > >
> > > > >
> > > > > ----- Original Message -----
> > > > > From: Coalbunny <coalbunny@vcn.com>
> > > > >
> > > > >
> > > > > > Yes, it is!  What about the innerds?  Can we get a
> > > > > spec sheet and
> > > > > > drawings if we want to make something similar?
> > > > > > Carl
> > > > > >
> > > > > >
> > > > > > Steven Mills wrote:
> > > > > > >
> > > > > > > Wow, that's quite impressive !
> > > > > > >
> > > > > > > It's a beautiful boat.
> > > > > > >
> > > > > > > --Steve
> > > > > > >
> > > > > > > ----- Original Message -----
> > > > > > > From: Jeremy Crawford <ISMASC@hotmail.com>
> > > > > > > >
> > > > > > >
> > > > > > > > If anyone hasn't checked out Bill's Sub lately
> > > > >  you should, the exterior is
> > > > > > > > done and it looks awesome.  Kudos Bill, you
> > > > > have done a fantastic job!
> > > > > > > >
> > > > > > > > Best Regards,
> > > > > > > > Jeremy
> > > > > > > >
> > > > > > > >
> > > > >
> > > > http://www.giffordmarineinc.com/sub/sub_5_16_03/Sub_5_16_03.html
> > > > > >
> > > > > > --
> > > > > > "Indeed, desire is the seed of thought, the prime
> > > > > force that activates
> > > > > > the mechanism of the mind." -- Kama Sutra
> > > > >
> > > > >
> > > >
> > > >
> > > > __________________________________
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