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Billy- There are situations where you do no-stop penetration diving (people do it around here all the time on shallow wrecks) and in those situations I will maintain that doubles are the way to go. I agree that double 72's are unsuitable for deep deco dives but IMHO are fine for "shallow" deco dives. Jim On 9/8/98 7:36 AM bdi wrote: >At 03:09 PM 7/09/1998 +0300, Teppo J Kurki wrote: >>Having gone from 10 l/300 bar tank to 2x7/200 and now own also >>2x10/200 here's my thoughts: >>15 l >>+ cheaper (probably) >>+ a little more gas >>- valves hard to reach (at the back of your neck) >>- awkward because of large diameter (at least in my experience) >>- need more weight >>2x7 l >>+ fit closer to your body => better balance >>+ reaching valves a lot easier, since they stick out >>+++ when you get larger doubles you can use _exactly_ the same setup and >>you will have already mastered the right reflexes >>- heavier on the surface >>- more expensive > > >TJK, the problem I have with the two configurations >mentioned, the 15 litre single and the 7 litre doubles >is in the ocean the 15 litre is too big. Unless the >user is an unfit, incompetent hoover with enormous >air consumption who shouldn't be diving, they won't need >all that gas on any reasonable singles dive- no overhead, >no deco ceiling, within bail-out reach of the surface. >A 10 litre is plenty big enough and doesn't give you the >management problems with the huge tank. > >I use a 65cu ft alloy on those kinds of dives and >that holds enough gas for me to earn a deco obligation. > >Also a 15 litre single is useless for caves. > >The two 7 litres are too small to do any reasonable >decompression or overhead dive, (rule-of-thirds gives you >only a bit over 900 litres of gas to turn-around). >At a useful planning consumption of 15lpm that's 12 minutes >at 40 metres. For all the convolution of doubles, and >two sets of regs, you might as well twin a couple of >10s or 12s and either get a reasonable dive in or leave >yourself a better margin. > >In the one post, this guy came up with the two worst >cylinder configurations imaginable. > > >rgrds billyw > >-- >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > ------------------------------------------------------------------- Learn About Trimix At http://www.cisatlantic.com/trimix/trimix.html -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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