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On Fri, 1 May 1998, KybrSose wrote: > Both tanks are tied together by a pressure hose. When that hose blows< and we > all know it will> You lose both gas supplies. You have to shut your primary > and the little bottle does not have a valve. If the second free flows you cant > shut it off and you are losing your only source of gas. A first stage failure > is covered by the little bottle but the dreaded tank neck o ring failure is > still there. But if you dont maintain your first, are you going to maintain > this thing? You cant hand it to another diver. > You are missing the point - only a moron would leave it attached to the primary during the dive. You boost the pressure when it needs to be refreshed, then disconnect the thing - easy filling. > Then there is the mindset behind this thing. You can't pay attention to your > gas supply? You shouldnt be in the water. If this is only for emergency use > then shouldnt it be bullet proof?? Again, you're missing the point. The presumption is that of main supply failure, which is a fair assumption if you have are diving singles. A check valve is pretty reliable - again, considering the nature of recreational diving. > If your plan is suck your main dry and > shoot straight up fine. If its suck your main dry and ascend on the pony fine. > But then you need enuff gas to ascend safely and a 13 is the edge of that > envelope. The outer edge. This will give you what ten twelve breaths from 120 > fsw?. Just slightly better than a spare air suppository. And we all know this > will wind up at that depth in the hands of that diver. > Al, it is always wise to do the math before making a strong statement - especially when you know you're dealing with people who do the math regularly. At an RMV of 0.5 cfm, you will get about three minutes at 120 fsw from an AL13. But in the event of a failure, as a recreational no-deco diver, you won't be at depth anything like 3 mins - you'll start the ascent immediately. If you start the ascent immediately, and assuming an ascent rate of 30fpm, you will use about 7.0 cu. ft of gas to get to the surface - about half of your AL13. Add in some minor decompression and/or a safety stop, and you still have enough gas. Same holds true even if you plan for a hooverish 0.7 cu. ft. RMV, although you are going to have to trim your safety stop (which is just that - for safety, and holds a very small probability of inducing bends if it is blown off - and the resulting bends are rarely if ever life-threatening anyway). > If you have a real pony you can switch to it and motor home. This is a > convolution, right up there with bungee wings, 80/20, metal to metal, poodle > jackets and curb feelers on the sides of your doubles. It's crap. > My point: dont't do a classic knee-jerk by sucking Hogarthian dick here. The right tool for the right job - and dive circumstances. I stick: for recreational diving, it's a whole different ball of wax - don't be so quick to pass judgement with the eyes of a technical diver - that is called hubris - or have you forgotten your roots? -Will -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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