Howdy Pierre
(Sorry if this is a repeat, but I did not see my previous reply show up.)
Check out "Austin Hardware & Supply" www.austinhardware.com. They have exactly what you described in several sizes. You have to get their printed catalog. See page 374.
Please correct me if I am wrong, but I think there will be considerable pressure, or at least could be. Being ambient and flowing air through the cabin and out the bottom means that the air inside the cabin will be at the same pressure as the weight of water at the bottom of the cabin. Since the top of the cabin is sallower the air pressure at the top of the cabin is greater that the water pressure outside the top of the cabin. I seems to me that you could think of it as an under water box, open at the bottom and full of air. The pressure at the top of the box is pushing outward in direct proportion to the height of the box. Consider if you turned your sub upside down and filled it with water. The top hatch will have to hold back that much pressure. I hope I am wrong about this because I have been fighting to build a hatch I can trust. I finally got the top on my boat last week and decided there was enough room to have the hatch open inward. That way the pressure will insure a good seal without elaborate latching. I plan to use 1/4 inch neoprene for a seal.
I also finally forked over the change for a domain name: www.submarineboat.com My hatch design is at the bottom of the "Putting the Hull Together" page.
Let me know what you think.
Doug Jackson
In a message dated 5/5/2004 12:16:47 AM Central Daylight Time, ojaibees@ojai.net writes:
Pierre, How about a tire inner tube?
Brian
----- Original Message -----
From: "Pierre Poulin" <pipo305@hotmail.com>
To: <personal_submersibles@psubs.org>
Sent: Tuesday, May 04, 2004 6:44 PM
Subject: [PSUBS-MAILIST] Hatch seal
> Thx Brian!
>
> But I know what seal I want. I don't know if it will work but my problem is
> finding it in a store...
>
> I want to buy basicaly a rubber hose with a flat side that can be glued.
> Since my sub is ambient, I imagine that there is almost no pressure on the
> seal...
>
> I will test that out and tell you guys!
>
> Thanks again Brian!
>
> Pierre Poulin
>
>
> >From: "Brian Cox" <ojaibees@ojai.net>
> >Reply-To: personal_submersibles@psubs.org
> >To: <personal_submersibles@psubs.org>
> >Subject: Re: [PSUBS-MAILIST] Pressure hull construction
> >Date: Tue, 4 May 2004 14:34:46 -0700
> >
> >Pierre (looking for hatch seal), What kind of hatch seal are you looking
> >for? What is your delema?
> >
> >Brian
> >
> >----- Original Message -----
> >From: "Pierre Poulin" <pipo305@hotmail.com>
> >To: <personal_submersibles@psubs.org>
> >Sent: Tuesday, May 04, 2004 10:55 AM
> >Subject: RE: [PSUBS-MAILIST] Pressure hull construction
> >
> >
> > > Hi Marten,
> > >
> > > You look like you are about to choose between an 1atm or an ambient sub.
> >Am
> > > I right?
> > >
> > > Maybe you have to ask yourself some basic questions like:
> > > What do you want to do with the sub?
> > > How many times per year do you plan to dive?
> > > Fresh or salt water?
> > > Depth of the dive? (100 feet)
> > > How many years you think your sub will be operational before you srap
> >it.
> > > Do you do scuba diving? If so, what do you like best about scuba diving?
> > > What you don't like?
> > > How will it be different in a psub?
> > > How will you tow the boat? Will it stay on a peer?
> > > What is the budget you plan for it?
> > > How many years you want to spend building/designing it?
> > > Will it be as fun for you to build it and gather parts as diving in the
> >sub?
> > > How long you want to be able to dive? (how many hours under the water)
> > > Any passengers?
> > > Etc...
> > >
> > > I think that answering those questions might help you choose the correct
> > > type of psub for you. I did the exact same thing and decided to switch
> >from
> > > 1-atm to dry-ambient.
> > >
> > > Once this is clear for you, then you will be able to move to the design
> >step
> > > I think.
> > >
> > > I hope it help a bit!
> > >
> > > Pierre "still looking for a hatch seal" Poulin
> > >
> > >
> > >
> > >
> > > >From: "Marten Liebster" <mliebster@tbteam.com>
> > > >Reply-To: personal_submersibles@psubs.org
> > > >To: <personal_submersibles@psubs.org>
> > > >Subject: [PSUBS-MAILIST] Pressure hull construction
> > > >Date: Tue, 4 May 2004 12:45:11 -0400
> > > >
> > > >
> > > >Those with 1 atm subs, how is/will be your pressure hull be
> >constructed?
> > > >
> > > >Was/will it be assembled by yourself or by a fabrication shop?
> > > >
> > > >Even if I were to design the perfect (unlikely) psub, I don't know if I
> > > >could trust myself or someone else with my life.
> > > >
> > > >Taking a trip in an airplane is different. There are industry and
> >federal
> > > >standards for the construction, usage and maintenance. Also there are
> > > >rigorous inspections. Plus, each plane isn't a one off creation. Also,
> > > >ignorance is bliss. :-)
> > > >
> > > >So even though I would spec out the proper material and proper welding
> > > >techniques, there's still that feeling of uncertainty. Even it was to
> >be
> > > >pressure tested to 2x operating depth, in the back of my mind would the
> > > >possibility of problems developing over time with things I had built
> >for
> > > >myself.
> > > >
> > > >Safety being the primary concern, this might be a deal breaker for me
> >(not
> > > >for others, it's a personal decision) for a 1 atm sub. I misquoted a
> >figure
> > > >in a previous posting - 100ft = ~6000 lbs of pressure per square foot -
> >I
> > > >incorrectly stated PSI. That's about the max operating depth I planned
> >to
> > > >be
> > > >at. Doesn't seem to allow for too large of a margin for a badly
> >fabricated
> > > >pressure hull.
> > > >
> > > >This has sparked another related question:
> > > >Would properly engineered (pardon my misuse of English) internal
> >framing
> > > >widen the margin for error?
> > > >
> > > >Thanks again to all who have helped me to better understand how a sub
> >is
> > > >properly designed and engineered.
> > > >
> > > >Marten
> > > >
> > > >
> > > >
> > > >
> > >
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