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I forgot to add that, if I need to blow air into the inflatable pontoons to surface, that I can add just enough air to make the sub start to ascend, much like some PSUBBERS do with there MBT's. That way as I rise, the air will fill the pontoons, hopefully slower, and also keep my sub from accelerating as fast in a dangerous manor, and put less pressure on the interior surfaces as the air expands and tries to get out of the expansion valves. If I'm really deep then I'll need a better valve design to deal with the faster changing pressures inside the pontoons when they get totally full and the sub starts to accelerate. But I still expect to need a number of expansion valves regardless. I would hate to have the pontoons pop when ascending, it they are my last option for lift. Your expanding air filled dreamer ;)' Regards, Szybowski From: brenthartwig@hotmail.com To: personal_submersibles@psubs.org Subject: RE: [PSUBS-MAILIST] Venting an Ambient Date: Thu, 4 Sep 2008 16:13:52 -0700 Hi Joe, This point you made below, is exactly what I want to figure out for my inflatable pontoons, so I can blow them at depth if I need to in an emergency. Most of the time I would only fill them up when I get back to the surface. "What would a cracking pressure of 0.5 to 2 lbs translate to in hull overpressure, and how many would be required to dump expansion in an emergency ascent from max depth." Your resident pontoon dreamer ;)' Regards, Szybowski From: joeperkel@hotmail.com To: personal_submersibles@psubs.org Subject: [PSUBS-MAILIST] Venting an Ambient Date: Thu, 4 Sep 2008 13:59:49 +0000 Someone asked about venting an ambient. I found some PVC check valves today which could quite possibly do the trick but I think you would have to ask two questions. What would a cracking pressure of 0.5 to 2 lbs translate to in hull overpressure, and how many would be required to dump expansion in an emergency ascent from max depth. Otherwise, these look pretty nifty! Joe |