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On Tue, 28 Nov 1995, Jason Rogers wrote: > >From memory (shaky ground) we were discussing ind/man in OOA situations. > I contended that an OOA (OOGas?) situation was less likely in an indie > than mani, and you said that OOA's were due to human error (in most cases) > and illustrated your point with a diver who has a gauge stick, and then > trusts it. So he uses 1/3, then switches to the other cylinder and > trusting his gauge, drains the whole lot. 1/3+3/3 in, 2/3 left, BANG, > he is dead. Yes, I think that was what I said, or something along those lines.. > I thought about this all day today at work. (if some sailor gets > a breathing set that don't go, we know who to blame: Ken!) > > I admit the indie diver is dead as a door nail, in a cave. But then > so is the manifold diver who follows his gauge. He breathes 3/3+3/3 > and then has *none* remaining to get out with. Not much difference. > *BUT* in OW there is a difference! I don't know about others, but I > retain not thirds, or exact halves, or halves + 200, but the amount > of gas needed to reach the first stop from the wreck. Hence if my > second cylinder should "just stop" be it from failure, or from > breathing it dry, there "should" be enough gas in the first cylinder > to get me back to the anchor, and up to my first stop. I think > that this is a major advantage for indies, over manis. A cave dive is to thirds. When you dive with a buddy, especially one you dive with regularly, your buddy should have an idea where your turn would be as well. Example, I sometimes dive with a guy who just doesn't breath at all, he's inhuman. He knows if he gets close to his third then I'm over mine for some reason. Another guy I dive with I know when to expect him to hit his third. If your brain doesn't function properly on a particular dive, at least with a buddy you have some form of backup. > The other point that I can remember concerned burst disks. I haven't > seen many go. A couple of Spare Deaths, while I was filling them. They > seemed more to just go "bang" than empty. A 150 cuft 200 bar (3000 psi) > and a 120 cuft 300 bar (4350 psi), both full. From memory, they seemed > to empty a *LOT* faster than 10 minutes. Just a few tens of seconds. > One minute at most. Of course I didn't time them. <some real interesting math snipped out> Ok, first. Some manifolds have two burst disks, yes. However, just because one blows doesn't mean both will. Quite often burst disks blow because they've been sitting in a valve for a long period of time and just get weak. I'd be willing to bet that only one of the two burst disks on those manifolds will go at a time. I've only seen about three burst disks blow. All were on single tanks. If I remember correctly they took at least 5 minutes to drain. They make a very loud noise and a mess out of a room with papers laying around in it. Maybe longer. We could run a test. Fill a tank all the way. Now open the valve wide open and time how long it takes for the tank to drain. I bet a burst disk doesn't go that fast. > If I've missed anything, or if you can think of anything else, I'll > have a go at that. It seems that Carl is going to *make* me use > a manifold if anyone can find any advantage to them for OW TMX. Jason, next you'll be telling me you want to do trimix fills based on a set flow psi over <x> minutes ;-) -- ================================================================== Ken Sallot "Your trim goes to hell when you run out of air" afn35346@af*.or* - Jim Wei http://grove.ufl.edu/~ken/
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