6cf or 13cf Pony

[Dr. Doug Ebersole]

Personally, for recreational limits I use a 13 cu ft -- as backup gas for my CCR! That's 27 cu ft of bailout (diluent plus pony). All kidding aside, it sounds like the consensus is either 13 or 19 cu ft. I agree that 6 cu ft is pretty worthless.

Hey, at least we're not talking about Spare Air again!

 

[ClayJar]

Hey, at least we're not talking about Spare Air again!

Spare Air is one thing that is named *precisely* what it is. The only thing I can never seem to figure out is where you get the inflator attachment so you can actually use it to fill your spare when the tire is low.

 

[RJP]

...40 and sling it

Yup.

 

[Jibeho]

I sling a 13.

All here quote the 30fpm assent limit Though I know this is the gospel now a days I just dug out my PADI OW dive manual from 1984 and my US Navy Diving manual Vol 1 NAVEDTRA 10476 (1978) Both of these list the standard ascent rate of 60fpm. Now we all know that figure went out the window years ago, I dived this rate and never had a problem. So lets say I'm at 90 and I need to bail because of any reason. You bet the farm that I will be ascending very close to 60 fpm till about 30 feet then slow a bit till 15 and stop.

What I trying to say is if you in an out of air contingency I seen no reason to needing to stick to the much more conservative 30fpm when we all know most of us have ascended at or near 60 fpm and lived to drink a post dive beer.

 

[ClayJar]

Regarding 60fpm ascent rates and not having had a hit, I'll gladly adhere to what we now regard as safe (including slower ascents and deep stops) when I'm planning for my safety!

DCS is statistical, not deterministic, and there is a very strong statistical justification for the "30fpm plus deep stops" recommendation which now exists. If I'm going to dive that when the dive goes according to plan, to plan not to dive it when the silt hits the fin is to be ignoring it at the very point when a DCS hit seems far more likely to occur.

Rather than plan to be more liberal with my profile if something goes wrong, I choose to plan to be even more conservative than usual, hence my rock bottom size at 19cf.

 

[lamont]

For me Lamont, the "what ifs" I worry about are getting to the places I dive. I've seen so many fatal car accidents in big Asian cities that I am worried about just getting there safely. Especially motorbikes. Very nasty.

I like my diving to be considerably safer than driving a car. Driving a car and exposing yourself to the idiots on the road is just the inherant risk that you must run in order to get to the dive site.

 

[meesier42]

wow, see what happens when I start something.
as for ascent rates, personnally 60 fpm deep (>60') and 30fpm shallow.

As for pony, I think you guys have helped me decide on the 13cf. I think its enough for me, afterall its a bailout bottle, things like safety stops are tertiary concerns by the time your on it, afterall you being safe includes NEVER being so loaded on nitrogen that 60fpm to the surface with no stops will kill you.
And of course Navy tables (yes I am a Navy diver too) are based on practice of thousands of divers being pushed to limits that you and I should never expirience, and they are MUCH longer than any of the other tables allow. And they are based on 60 fpm ascent rate with no stops.

 

[mheaster]

My first (current) Pony bottle is a 19 CU foot. I would not even think of a smaller one!

I am almost convinced to look for a 30-40 cu foot one?

If you believe a 19 to be too large, I would highly suggest borrowing one, dive in a relatively shallow, benign environment (quarry or such) to get comfortable with it and see how easy it is to forget you are carrying it when at depth.

If you sling it, it is not cumbersome or a burden! Just have to make minor adjustments in weighting/trim.

Good Luck!

 

[lamont]

afterall you being safe includes NEVER being so loaded on nitrogen that 60fpm to the surface with no stops will kill you.

Actually, I'm doing dives so close to the NDL limit now that I assume that doing 60 fpm to the surface with no stops will probably hurt me, and I'm interested in doing diving in the future where 60 fpm to the surface with no stops certainly would kill me...

 

[drbill]

I agree that a properly mounted 19 cu ft pony is no problem. I'm not even aware it is there (except for charging the system by opening the valve at the start of my dives.