What size pony do you use?

[GrumpyOldGuy]

Supplementary question: Have you ever had to test the sufficiency of your pony? Did that cause you to change / modify your opinion?

TIA

If you mean have I drilled with it vs doing calculations, yes. I have done multiple ascents from 80' (the deepest local dive). The amount of air to ascend under the unstressed conditions was very small, it was possible to do it all including a S/S on my tiny/undersized 6' bottle. I have done the ascent without mask to add a bit of stress (there was an up line marking the s/s location). Later I did it with an SMB deployment (still no mask), I did this with a 13 and used most of it under the same conditions (I.E. I added task load and gas use doubled).

I did not change my opinion, I still maintain from rec depths you modify your ascent rate and s/s plan to match what gas you have. Emergencies once they happen are unpredictable and if you are in recreational mode you have lots of options. You can trade of capacity for ease of use / small size. Once you cross to overhead / deco, then your options becomes much more limited and your backup plans need to be more robust.

 

[scubadada]

Slung 19 to recreational limits. More than adequate for my air consumption. To each their own.

Supplementary question: Have you ever had to test the sufficiency of your pony? Did that cause you to change / modify your opinion?

TIA

I do the same conservative calculation that lowviz does. Over the last 235 dives, my average SAC is 0.37, double that to 0.75 (15% higher than any SAC I've had). Spend a minute at 130 feet, ascend to 15 feet at 30 feet per minute, spend 3 minutes at 15 feet and then slow ascent to the surface. For me, that's 17 cu ft, leaving about 300 psi in my 19 cu ft pony.

I've never had to use my pony in an emergencey. I do practice deploying it frequently and am confident that would go smoothly. I keep it filled to 3000 psi+ and have an SPG on a short hose rather than a button guage. I very rarely dive to 130 feet, a deep dive for me is more like 110-115 feet and that is max depth. If push came to shove, there is obviously some flexibility in the ascent rate and the safety stop. I'm confident in my redundant air supply.

A 19 or 30 cu ft cylinder is a good choice as a pony for recreational diving. Individual SAC and degree of conservatism will be the decider.

Good diving, Craig