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Greetings and Welcome to the Submadman Group Alan, you'll find a bit of every thing here. I've got some snow I can sell you if you cover the shipping. A large plate with many holes might be a good option, I'll have to as my local expert about it. Many of the inflatable boats and pontoons out there can't take much internal pressure. I might need to have my friend over at Seamtek make me a extra heavy duty pair of pontoons from scratch. Installing new outlets on finished inflatable pontoons might not be easy for him. I'm also interested in designing these so they can vent properly on a rapid accent. It helps to only add just enough air into them to get your sub to start to ascend, this way your sub won't be moving towards the surface near as fast when the pontoons are trying to vent the extra pressure once there pressure goes over the set pressure that the expansion valves are set at. I was thinking about how my last configuration with just two outlets in the top side of the pontoons, towards the subs pressure hull that are plumbing into the 2 inch OD aluminum support pipes, then those pipes having two downward facing 1.5" ID expansion valves, which makes a total of four expansion valves per pontoon, might not be the best option. Now that I'm thinking of using a vacuum pump to pull all the air out of the pontoons before diving, I only need one 1.5" ID outlet in each pontoon for filling the pontoons with air from the SCUBA tanks or the vacuum pump in reverse. I found a 12 volt vacuum that looks easy to plumb for both suction and filling the pontoons at the surface, then using the HP air at depth. http://www.nrsweb.com/shop/product.asp?pfid=1705&deptid=1114 So now all I'm left with is how to configure the expansion valve(s). If I could find a nice big 3" or 4" low pressure expansion valve that could be attached directly to the pontoon that might be all I need. Other wise I'm thinking of adding two to four 1.5" ID outlets with one expansion valve one each. These could be positioned just like the two outlets that are on the side of the pontoon boat in the picture in the link below. But with the outlets on the side that faces my main pressure hull. The 2" aluminum pontoon mounting frame and side thruster tangle guard assembly will hold onto the pontoons much like in the below picture, except I'll weld on a section of aluminum sheet stock and Rhino coat it, so I can stand on top of the pontoons with out worrying about damaging them, and for the pontoons to be sucked up into before diving. I will now have loose pipe ends like that either, since they will rap around and be welded into each other for a clean look, much like the ski boat towers. http://www.jpwinc.com/index.php?page=photo&photo_id=317 http://www.seamtek.com/ Regards, Szybowski From: alanjames@xtra.co.nz To: personal_submersibles@psubs.org Subject: [PSUBS-MAILIST] inflatable pontoon configuration Date: Sun, 14 Dec 2008 22:29:54 +1300 Hi , I'm new to the group, am designing a small 1 atmosphere sub. Have been diving for 20+
years and reside in Auckland, Newzealand.
I've been looking at the pontoon idea. One of my reservations is that the pontoon material
will be stuffed into any outlet/inlet hole at say 180 psi at 300ft.(a 2"diameter pipe was mentioned)
I'm concerned at it rupturing in time. Had thought of an arrangement of a plate with multiple holes
in it over the inlet/outlets. Any thoughts on this?
regards Alan
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