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Re: [PSUBS-MAILIST] Bill Gifford's Project
>From: Dan H. <JMachine@adelphia.net>
>
> I don't really have answers to your dual hull design.
>.............snip...............
Thanks Dan,
My curiousity was more 'textbook' than practical.
Ever since the topic of Bill's pSub came up I've been seeing
propane tanks everywhere I go. They seem to come in a
variety shapes and sizes. I *might* consider designing an
ROV around one, a shallow submersible, or wetsub.
Checking past messages in the archives, there seems to be
a general consensus to stay away from designs using propane
tanks.
I've been doing a little research on framing and stiffening rings.
[ along with all the other topics brought up here ; batteries, propulsion,
ballasting...etc. whew! ]
Has anyone seen the movie "U571" ? I've only seen it once on T.V.
I could swear there is a scene where the sub is under depth charge
attack and the compression shock exposes [ or outlines?] the frames
along the hull. I was quite surprised by that added special effect.
Does anyone have a video or dvd of "U571" Perhaps someone could
review it and this particular scene? Or maybe I just imagined it.
--Steve
>
> ----- 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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