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Interesting thread. Maybe would have been better to focus the question more, i.e. for bail out possibilities only, on recreational dives - as the answers are hitting on a variety of purposes.
When I first looked at this question for myself, I figured cost was not an issue. 6, 13, 19, 30, 40 - they all use the same reg & sling, and the differences in cost was negligible compared to the rest of the kit. Then I looked at the equivalent of the tanks to that of a 80 CF @ 3,000 psi, is that makes any sense...?
Then I looked at weight differences from a chart like this one Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan
In the end, it's a personal call - but I still think anything less than 19 is just insufficent.
When I first looked at this question for myself, I figured cost was not an issue. 6, 13, 19, 30, 40 - they all use the same reg & sling, and the differences in cost was negligible compared to the rest of the kit. Then I looked at the equivalent of the tanks to that of a 80 CF @ 3,000 psi, is that makes any sense...?
6 CF is about 225 psi equivalent of a 80 CF;
13 CF is about 488 psi equivalent of a 80 CF;
19 CF is about 712 psi equivalent of a 80 CF;
30 CF is about 1125 psi equivalent of a 80 CF.
I wondered how much I really needed for a safe ascent when caca hits fan at depth? I thot anything less than 19 CF was silly.13 CF is about 488 psi equivalent of a 80 CF;
19 CF is about 712 psi equivalent of a 80 CF;
30 CF is about 1125 psi equivalent of a 80 CF.
Then I looked at weight differences from a chart like this one Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan
Starting with the 6 CF @ 2.7# comparing Luxfer tanks without valve...
13 CF = 5.9# - only 3.2# more but - remember I didn't like the volume available
19 CF = 8# = another 2.1#
30 CF = 11.6# - another 3.6#
I thot about my old cowboy knees, me walking around in a 7 mil suit with 30# lead, back tank @ 31.4#, valves for both tanks, BC, lights, other gear and I decided while the 30 CF looked nice on the shelve, that extra 3.6# did not. 13 CF = 5.9# - only 3.2# more but - remember I didn't like the volume available
19 CF = 8# = another 2.1#
30 CF = 11.6# - another 3.6#
In the end, it's a personal call - but I still think anything less than 19 is just insufficent.
Yep, if I could gear up and un-gear under water, I'd agree. I have to walk to the steps tho, then climb them out later. Eh, your knees are probly younger and never have been kicked by obnoxious cows.After a bunch of math I picked a 19 CF...........small, easy to carry and sling..........
Hindsight is always 20/20 so if I had to do it again would have picked a 30 CF.......
Underwater a 30 and 19 are virtually the same and the benefit of much more air........
M
I just find that silly toy insulting, as you have to remove the valve to fly it, so it's only O2 clean on purchase, never again - as no one is going to partial pressure fill it anyway. You can fill any pony with blended Nitrox 36.The O2 clean one?