Re: [PSUBS-MAILIST] Inflatable Pontoon Configuration Options

[irox <irox@ix.netcom.com>]

Hi Brent,

are you planning on removing the inflatable pontoons before diving?

I've consider the inflatable pontoon option before, but one of the draw
back I thought I'd run into is getting all the air out of them.  If they
are on the sub during a dive with air trapped in them, the buoyancy of
the sub will change as the sub goes deeper.  A solution was to detach the
pontoons and bring them into the sub when diving - althought the extra
work an storage requirements are kind of a draw back of that idea.

I like idea of cutting the bottom out of a zodiac boat, adding some
attachment points to the sub so the zodiac can be attached to the sub
when it's on the surface.  Detaching the zodiac when ready to dive
and leaving it on the surface (with a dive flag).

Cheers,
Ian

-----Original Message-----
>From: Brent Hartwig <brenthartwig@hotmail.com>
>Sent: Dec 13, 2008 4:47 AM
>To: PSUBSorg <personal_submersibles@psubs.org>
>Subject: [PSUBS-MAILIST] Inflatable Pontoon Configuration Options
>
>
> 
>I left out that I'll need two venting valves next to the hull and thru hulls for them, just above the tubing attachment points on the hull.  I can see now that it might be better to add two outlets at the bottom of the pontoons and place the expansion valves there instead, so to be able to blow any water out that might get into them. There are floats available that contain two tubes inside, one in front and one in back. These might be a better option for several reasons.
>Regards,Szybowski
>
>From: brenthartwig@hotmail.comTo: personal_submersibles@psubs.orgSubject: RE: [PSUBS-MAILIST] Removing Front MBTDate: Sat, 13 Dec 2008 01:30:34 -0800
>
>Hey Frank, I sold my sewing machine for a MIG welder, so I'm SOL.   ;)' I have a friend that is a real pro and making these type of floats and designs and manufactures the very custom machines that Zodiac and others use. So I was thinking of having him make one from scratch, but he and I decided that with all the very nice premade units that are available, we could likely find one that we could add two large top custom vent holes in and be done with it.  Since I'm configuring these to be blown at depth if needed in an emergency, it's more work to calculate and design.  At the moment I'm planning to install two 2 inch ID basic vents that I can attach a short flexible hose to, then that hose attaches to one of the 2 inch schedule 40 aluminum tube supports for the tangle guard and pontoon standing platform. This way I don't need a extra hose on the outside of the sub, since that said support tube can serve double duty.   Then as the tube goes toward the sub, there is a downward facing T added to the tubing with a large volume low pressure pop off valve facing downward attached to the bottom of the T. This expansion valve will be set at the proper level needed to keep the pontoons inflated at the surface.   Since there is one expansion valve on each of the two tubes that come towards the sub, they should keep me from popping the pontoons during surface ops.  Then for blowing the pontoons at depth I feel I need to add another set of T's right next to the sub that go down well below the bottom of the pontoons and that tube will be curved to the shape of the hull, and at the bottom of that tube will be a large valve that is attached to a thru hull at that point. This is so I can operate it from inside, just like a MBT vent valve in the conning tower.  I obtained that basic idea from the two tubes that come out of the bottom of the large plastic pipes with caps, that were used on the Dennoch sub. http://www.psubs.org/museum/museum_sfphotos.html For filling the pontoons with air from the SCUBA tanks, I'll have a thru hull going right thru were one the the tangle guard support tubes attaches to the side of the sub. This is a little more work, but will give me a cleaner look when finished.  That is the concept I have worked up to this point. I'm sure it will need some fine tuning, once I have made a full assembly model of it, I'll have you guys take a look at it, as well as my local expert.Regards,Szybowski
>
>From: ShellyDalg@aol.comDate: Thu, 11 Dec 2008 16:48:46 -0500Subject: Re: [PSUBS-MAILIST] Removing Front MBTTo: personal_submersibles@psubs.org
>Hi Brent. Seems like you could make your own pontoons fairly easy and cheap. As long as they weren't necessary to ascend. You can buy rubber sheeting and  also tubes off the shelf in pretty much any thickness you want. Making a big inner tube type pontoon should be pretty simple, and the same guys who sell the tubes/sheets have several types of glue that bond stronger than the material itself. That may be a good way to save some money, and give you more flexibility on the shape.
>You could also make a nylon bag for it to protect it from abrasion and sunlight. Just sew it together on a regular sewing machine. Frank D.
>
>
>Make your life easier with all your friends, email, and favorite sites in one place. Try it now.




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