runsongas
Contributor
19 is fine as pony bottle, but a 40 is more useful later on because you can clean it for a deco bottle. resale also better because of that. that also means you might be able to find a 19 used for cheap.
Pony bottle
- Thread starter rabe
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mi000ke
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Rather than guestimate the appropriate size bottle, if you know your SAC rate you can compute the amount of air you will use to ascend from your deepest depth assuming it's just being used for bail out, and assuming 30'/min ascent and a safety stop at 15', plus a couple of minutes at depth to get sorted out, then double the whole thing to account for a stress-related increase in SAC rate.
For example, if your deep point is 100' (4 atm), then it's 4 x SAC for 2 minutes, then about 3 min to ascend to 15' X about 2.25 atm ((4 + 1/2)/2) x SAC, then 3 minutes safety at .5 atm X SAC, then a bit to get to the surface, then double the whole thing. I rounded off some of the numbers. [I'm sure someone will check my math to make sure i did this right.]
I have a SAC of about .4 to .45, so for me it comes to almost exactly 13cf (always used as a bailout and not part of my gas plan), and that's what I sling (and I'm never at 100' too often or too long). I'd probably carry a 19 just for a buffer if my back could handle it out of the water, but that's a different issue...
For example, if your deep point is 100' (4 atm), then it's 4 x SAC for 2 minutes, then about 3 min to ascend to 15' X about 2.25 atm ((4 + 1/2)/2) x SAC, then 3 minutes safety at .5 atm X SAC, then a bit to get to the surface, then double the whole thing. I rounded off some of the numbers. [I'm sure someone will check my math to make sure i did this right.]
I have a SAC of about .4 to .45, so for me it comes to almost exactly 13cf (always used as a bailout and not part of my gas plan), and that's what I sling (and I'm never at 100' too often or too long). I'd probably carry a 19 just for a buffer if my back could handle it out of the water, but that's a different issue...
I think for the moment a 19 is more than fine (and I'm pretty sure i'll never use it, but better safe then sorry).
@run: For a deco bottle is not that time yet and I'll deal with it later
@rabe - If I am reading you correctly and I think I am, then don't hesitate to go with the 19cf and sling it the way you have intended. You have clearly done some research for your intended use and I believe you will be happy and it will meet your needs!
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