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Hi all, Tom said: Sorry to change the subject but there are some things in your post that I simply do not understand. ***** OK I'll try and explain myself better ***** Manifolds are just plain stupid >in the open water environment. They *depend* on a tight buddy system, >and while you may be able to manage that in a nice still friendly cave, >you *cannot* do that on an ocean dive. I do OW wreck dives off the New Jersey coast and I use a manifold. I can reach all three valves with no assistance. What I do not understand is how a manifold *depends* on a tight buddy system? I am usually with a buddy in the water, but I am there to take care of myself and in NO way am I dependent on my buddy, especially with a basic piece of equipment like a manifold. ***** I wasn't talking about operating the manifold, I meant that a manifolded system is a *SINGLE* gas supply. I understand that you can operate it by yourself. I contend that single gas supply systems are not suitable for solo diving. Also we are talking about *trimix*. Consider this. Posiedons are rated at 1800L/min of air flow at the surface. Depending on the richness of your trimix, you can expect to double this flow on the surface, and further increase it at depth. Flows in the order of 5000L/min would not be unexpected. ( >150cfm ) I'm not trained in isolation manifold diving, but from what I've read here, the drill is to shut down the isolation valve first, then shut down the bad reg, then switch regulators. (correct me if I have this wrong) Now there have been posters who have said that they can reach the isolation valve simply by loosening the crotch strap, lifting the set from behind with one hand and then reaching over their shoulder. (wow!) Let's forget about them (Darwin's problem) and talk those who can reach the valve with one hand. 3 seconds to recognise the problem. 3 seconds to change the grip on what ever you were using so that you have a free hand. 10 seconds to close the isolation valve 3 seconds to id the correct "bad" reg 10 seconds to shut down the bad reg That equals *75 cubic feet of lost gas* if everything goes perfectly. Perhaps we have a diver who has now been holding his breath for 30 seconds (stressed). Another 10 seconds to switch regs (don't forget that this is an unusual event for him, rather than something he has done thousands of times) (very stressed now). What is his RMV, double? triple? Will his RMV go down as he collects himself? Say he takes 1 minute to collect his thoughts. His RMV has gone up from .75 cuft/min to 1.5 cuft/min. At 300 ft this is another 15 cuft of lost gas. That's 90 cuft of lost gas (even if his RMV returns to normal after only 1 minute). Are you telling me that you carry more than 100 cuft of "spare" gas? (haven't even considered sheared off manifolds) Compare that to the independent solo diver, who has a freeflow. He says "Oh Bugger", switches regs and turns the dive. Knowing that he has plenty of gas in his remaining cylinder, his RMV remains normal. A few months ago I was wriggleing through a cave passage when the reg I was breathing just stopped. First reg failure I've ever had. I was alone, I had a deco ceiling, and a rock ceiling. I switched regs, and turned the dive. Know what my over riding thoughts were? Shit, I hope I can get the parts I need to fix this thing out here. What would have been upper most in my mind if I had lost 90 cuft of gas at the same time? ***** >If you think you can climb an anchor line in a 6 knot current while >shareing gas (even with the silly 7 foot hose!) you are *nuts*. The >drag on the hose *alone* would tear it out of your mouth! Although I am not cave certified, I have been exposed to the genre through friends who are cave divers and some cenote dives in Akumal. I "borrowed" the idea of using a longer hose, primarily because in a situation with strong current or suddenly changing seas the diver on the long hose is much less an impediment to the other diver. I've had to use my long hose twice, both times with total strangers, neither time was there any problem climbing the anchor line. I went first and the other diver just seemed to follow wherever I went :), despite the fact that the second time the seas had kicked up quite a bit and we were getting bounced all over the place. My first question, what are ****** I contend that as a solo diver, I'm responsible only to myself. What the Brits call "my air is my air" rule of gas management. I consider the risk of sharing gas in a strong current to be *great* and I would prefer to dive well away from those who may place this demand on me. If I see a diver using a manifold, I swim away from them. ****** you doing diving in *6 knot* currents and second, if the divers are spaced properly why would the hose be torn out of your mouth? ***** 1. Having fun. 2. Because the drag on long thin cylinders is *huge*. a diving hose is a long thin cylinder. There is a mecanical advantage when a flexable system is loaded in the middle (water drag) and held at both ends (cylinder/divers teeth). ***** >OW trimix is no place for the buddy system, and solo diving is >no place for manifolds. Make no mistake, with a manifold system >on a solo dive, a major failure will mean you *will* die. A major failure on independents will ensure that I will *NOT* die? I have a hard time following that logic. ****** That isn't what I said. I said a major failure on a manifolded system will kill a solo diver. On an independent system you need *two* major failures before the diver is deprived of a gas supply. Cheers Jason =:)
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