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Hi, I thought Carl would add some interesting things to this debate and he has. Richard has already said things better than I can, but I feel I should add my two cents to Carl's response. (and you can't stop me anyway) ******** Now, on this manifold issue :^) I *WAS* concerned about the same things as you Jason (shearing of the manifold - damage - etc),but the REAL test of which is better would be which one has which one has more accidents/fatalities. Now, not knowing the exact numbers I can't provide a great answer, but, I'll make some obsevations. First, why do all the big time cave divers in the US use manifolds? I suspect George might have something to say on this (or Charles). ******* Richard said, (more or less) because they dive in proper buddy teams. I agree with that. Fine in a three man buddy team. George said (after a long thing on equipment setup) "your buddy is your redundancy" and I agree with that. Trouble is that in OW trimix (the subject of this discussion) buddy diving just doesn't work. I don't think that anyone here dives OW with *real* buddy systems in place. Ie. in touching distatance at all times, or connected by a buddy line. I think for this type of dive you have to consider it a solo dive, and rig accordingly. Solo diving a set up that relies on a buddy for redundancy isn't very sensible in my book. ******* Second, having dove twin 100's as independants I agree with Jason that switching tanks just isn't that hard. Some of the "independants" problems have come from switching to the wrong gas at depth. SO, if you're carrying several gases and switch on your back gas several times, you're definitely increasing the probability of getting the wrong reg - better make damn sure you know which regs are where... ******* Ok, but if you have all your bottom gas back mounted, and all your deco gas side mounted (as many do), then how can you get them mixed up? Anyway, if you are *trimix* diving, you damn well better have your reg selection down pat. ******* Third, just HOW MANY manifold have been damaged on a dive? ******* I only *know* of one. How many do you need? They cost money, trap line, have mass, can dump gas, create drag and have no useful function. Surely you would be better off carrying a christmas tree with you. They cost less, can't dump gas, have a *zero* failure rate and have no useful function (just like a manifold), oh and create drag and trap line too! ******** Fourth, in the blown reg case with the isolation manifold... You *could* dive with the isloator MOSTLY closed, that way pressure would be equalized BUT, in the even of a catastrophic failure on on side the cross leakage would be drasically reduced. NO one has mentiond this yet, why? ******** How closed is "mostly closed" and how much would it take to have it bumped "fully closed" or less closed, ie more open? Fifth, Jason said... >It can be a killer too. I know of a diver who practiced opening the >isolation valve in shallow water before setting out on a big dive. >(sensible precaution!) Trouble was that really deep, he needed his >wings fully inflated. Discovered that he couldn't reach his valve! >(at +100m, in a current, on a line, after he exahusted the first cylinder) Well, why couldn't he have switched to the reg that was on the other side of the manifold - just like independants??? You DO assume that divers have regs on each side of the isolator, right??? I think your alarm here was someone panicing and forgeting that he ALREADY had access to that gas OR, he screwed up by not having a reg on both sides. ******* Yep I think you are right on this. I think he got over task loaded. Which sort of backs me up on my feeling that manifolds have a lower task loading normally, and a higher task loading in an emergency. ******* Finally, I must agree with Ken, this is a DIFFERENT debate than the pony/SD issue. Ken meniond a blown burst disk - I think we went through this debate before, right, what would bent gaster, HP, LP, or burst disk (maybe the burst disk wasn't in the discussino before). We all agreed that LP would bent faster because it's designed to flow a lot of gas to the diver in need, while both other methods are a "slower" (relatively speaking) event. Again, I agree with Ken, people have died from switching to the wrong gas at depth. WIth manifolds, this would NOT have happened. How many people have died from manifold failure of ANY reason??? ******* If an american diver is discovered dead, while solo diving, using a manifold, what is the cause of death? Is it put down to solo diving? or is it put down to solo diving, without a backup gas supply? How many people have died from running out of gas???? With independents *this* wouldn't have happened. Getting no gas out of a cylinder is a much stronger warning than a needle pointing at a predetermined point on a gauge. With manifolds, you get that strong warning about 1 minute before you breathe water. Cheers Jason =:) (This isn't a flame either) ;)
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