Would there be enough air in a thirteen cubic foot bottle to make an ascent from 130 feet, which would include a one minute stop at 30 and 50 feet and a three minute at 20, for a person like myself who is pretty easy on air most of the time? 
13 cubic foot bottle
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Blackwood
Contributor
How fast?
Assuming an ascent rate of 30FPM, multiply your SAC rate (in CFM/ATM) by 22 (in ATM*min). The result will be the (approximate) computed gas usage in CF.
edit
disclaimer: that ATM*min number above only applies to the specific profile in the OP
end edit
Assuming an ascent rate of 30FPM, multiply your SAC rate (in CFM/ATM) by 22 (in ATM*min). The result will be the (approximate) computed gas usage in CF.
edit
disclaimer: that ATM*min number above only applies to the specific profile in the OP
end edit
Last edited:
OldNSalty
Contributor
Just enough might not be good enough...but then again, if a 13 is the largest you are willing to carry I suppose that is better then no pony at all.
R
redacted
Guest
I also use a 13 as it packs well for flying but you would be real tight from that much depth even with a SAC below .5. Unless air travel is a requirement, a 19 should do the job with a buffer.
I do take my 13 over 100 ft but never while solo where it would be my only option. I have done practice ascents (30 fps) from 85 ft with 1 minute stop @ 30 ft and 5 min rest stop and plenty of air to spare after I reboarded the boat. I also have an equalizer hose so I can keep that 13 at or over 3000psi. With a 19, that is not quite as important.
I do take my 13 over 100 ft but never while solo where it would be my only option. I have done practice ascents (30 fps) from 85 ft with 1 minute stop @ 30 ft and 5 min rest stop and plenty of air to spare after I reboarded the boat. I also have an equalizer hose so I can keep that 13 at or over 3000psi. With a 19, that is not quite as important.
Based on an average "relaxed" breathing rate of say .75 cf min. (which is probably high, but for argument's sake) an ascent with the stops you've noted... probably not. I'm figuring it'd take "roughly" 13.9 cf. to make that ascent.
A 13 cf will get you to the surface from that depth if you make a 30 feet per min. ascent with no stops.
If you feel it is necassary to do all of those extra, extra conservative and redundant deco and safety stops, then no, it too small. Get a 40 cf and sling it.
If you feel it is necassary to do all of those extra, extra conservative and redundant deco and safety stops, then no, it too small. Get a 40 cf and sling it.
Rocketmahn
Contributor
I dive with a 19 cuft. pony.
It has one of two purposes -
one to get me a short distance over to my dive buddy so I can use his octo,
or,
two so I can breath it to the surface.
My bailout ascent plan is to slowly head up to a 15' safety stop and hang around for 3 minutes, or until the 19 cuft pony is out of air (whichever is shorter) and then surface.
On paper I can "Almost" make an ascent from 130' with a 1 minute deep stop, slow ascent rate, and 3 minutes at 15 ft under STRESS all on a 19 cuft pony so I figure drop the deep stop since I'll use less air at shallower depths anyway.
It has one of two purposes -
one to get me a short distance over to my dive buddy so I can use his octo,
or,
two so I can breath it to the surface.
My bailout ascent plan is to slowly head up to a 15' safety stop and hang around for 3 minutes, or until the 19 cuft pony is out of air (whichever is shorter) and then surface.
On paper I can "Almost" make an ascent from 130' with a 1 minute deep stop, slow ascent rate, and 3 minutes at 15 ft under STRESS all on a 19 cuft pony so I figure drop the deep stop since I'll use less air at shallower depths anyway.
dumpsterDiver
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You need to specify the ascent rate and the sac rate. the rest is easy. Also, if you want to take a small pony bottle to that depth, you might consider blowing off the deep stop and possibly the shallow one as well.
I use a 6 cu-ft for dives to 130, but it is designed to save my back by minimizing weight, but it will not provide an oppportunity for safety stops.
I use a 6 cu-ft for dives to 130, but it is designed to save my back by minimizing weight, but it will not provide an oppportunity for safety stops.
I'd also factor in the idea that if you're at 130ft and have just had the unpleasant surprise of taking the LAST available breath off the single tank on your back - and your buddy is no-where in sight - you're SAC is gonna go up just a tad.
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It's what I use as a pony. I've got a SAC of about .5. When I run out of air at 130 feet, I'm buried in deco. A minute at 50, 30, and a safety stop isn't going to help. If I have a primary reg failure, a minute at 50, 30, and 3 at 20 isn't necessary.
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