Pony's: 30cf LP AL Versus 23cf HP steel??

[Mr. Bubble]

I have a 30CF LP aluminum pony bottle, and have reciently discovered the existance of a 23cf HP steel. Would the steel give me more air after its all said and done? I typically use it for wreck diving and limited deco...safety bottle. Deep dives etc.....

The steel is a bit more compact, but also a slight bit heavier. I use steel 120's or steel doubles on my backplate.

What you think? More air? Should I go for it?

 

[Lehmann108]

CF are CF regardless of the psi, right? So a 30 CF pony will give you more gas than a 23 cf pony. The difference would be in the buoyancy characteristics of aluminum vs steel.

 

[Kirkandtiger]

You're missing some information here. At what PSI? I assume the aluminum 30 is 30 cf at 3000 psi. Let's assume the HP 23 has 23 cf at 3500 psi. In order to get 30 cf into the steel tank, you'd have to pump it up to about 4600 psi. I'm a big fan of overfilling, but that's a lot in a little tank. - Kirk

 

[Divin'Papaw]

Stick with the AL30. It's much easier to manage from a buoyancy perspective. Goes from slightly negative to slightly positive, but only by a pound or two.

 

[NorthWoodsDiver]

Yeah I started with a steel 19 cause I figured it would be better from a buoyancy standpoint but I was way wrong, stick with aluminum for all you sling/stage/pony/deco bottles.

BTW 30 cubic feet is alot more air that necessary for most dives on a recreational level so you might want to pick up a 19 for your light duty diving and reserve that 30 for deco gasses or something.

 

[Divin'Papaw]

Yeah I started with a steel 19 cause I figured it would be better from a buoyancy standpoint but I was way wrong, stick with aluminum for all you sling/stage/pony/deco bottles.

BTW 30 cubic feet is alot more air that necessary for most dives on a recreational level so you might want to pick up a 19 for your light duty diving and reserve that 30 for deco gasses or something.

I actually like the 30 for one simple reason. It doesn't have to be completely full to meet the needs of most recreational dives. If I'm diving below 100' I like to make sure it's full. However, if I'm using it in the 50-90' range, it has pleanty of gas to get you safely to the surface in an emergency even at 2000 psi.

 

[DA Aquamaster]

I use AL 30's for my deco bottles. They handle very well in the water and offer more than enough gas for deco dives in the 150 ft /25 to 30 minute range with run times around an hour with 50% and/or 100%.

An AL 40 handles just as well and the extra lenght goes mostly unnoticed (but I got a great deal on five AL 30's) but the math is super simple with an AL 30 as 100 psi = 1 cu ft for planning purposes.

For use as a pony bottle on recreational dives you could use it most of the season before you'd lose enough gas from each hook up and disconnect to reduce the amount of gas to the point where you would need to top it off. And it is enough capacity where you could practice switching to it now and then without having to top it off after a dive where you practiced using it.

With regard to steel pony and deco bottles, I have met very few divers who have liked them compared to Al tanks due to their negative bouyancy traits. You have to weight yourself on the assumption the tank(s) will not be on you at a safety stop so you need enopugh lead to stay down without them, but then when you add their negative bouyancy and the negative bouyancy of the gas they contain when full, you end up badly over weighted.

 

[Mr. Bubble]

Thanks guys....I really appreciate the info.