Diving with a pony tank - bouyancy questions.

[Mat K]

I’ve got all the bits and pieces to rig up for a 3 litre pony for 20m+ dives. (I always have to rely on instabudies - doesn’t gel with my somewhat risk averse tendencies).

I’m planning to clip it and sling it at the front, reg and spg bungeed.

Now, a full steel tank rigged up weighs about 7kg. My thoughts were, that surely I don’t compensate for all of this by wearing less lead (if I have to ditch the pony in an emergency) otherwise I may pop right up?

I’ll be diving with ops that rent steel and alu tanks. Does anyone know what the bouyancy characteristics are when full and empty? Any help would be great.

 

[Diver0001]

Personally, the first time I dived with it I wouldn't change anything. After that, dial it in.

R..

 

[DevonDiver]

Does anyone know what the bouyancy characteristics are when full and empty? Any help would be great.

There's some specifications here: Cylinder details. And you can Google to find most manufacturers specifications, which include in-water buoyancy characteristics at varied gas pressures.

Aluminium tends to be the popular choice amongst tech divers.. it contributes better to the balanced rig approach.

 

[mmerriman]

There's some specifications here: Cylinder details. And you can Google to find most manufacturers specifications, which include in-water buoyancy characteristics at varied gas pressures.

Aluminium tends to be the popular choice amongst tech divers.. it contributes better to the balanced rig approach.

I've got a 2# swing with my alum 30 full to empty. I think I don't need to do anything to accomodate that weightwise.

 

[KentB]

Ive reently picked up a 30al pony. I haven't changed my weighting and don't feel i'm "overweighted" to be honest but I dont have very many dives with it either.

 

[rabe]

I’ve got all the bits and pieces to rig up for a 3 litre pony for 20m+ dives. (I always have to rely on instabudies - doesn’t gel with my somewhat risk averse tendencies).

I’m planning to clip it and sling it at the front, reg and spg bungeed.

Now, a full steel tank rigged up weighs about 7kg. My thoughts were, that surely I don’t compensate for all of this by wearing less lead (if I have to ditch the pony in an emergency) otherwise I may pop right up?

I’ll be diving with ops that rent steel and alu tanks. Does anyone know what the bouyancy characteristics are when full and empty? Any help would be great.

Try initially without changing your lead load...
I have a 2.7 L alloy and I didn't change my set up

 

[Fastmarc]

I'm in the process of getting and came across this on the Catalina site for the 19cf (2.7L) tanks. Full: -1.5 lbs, 500psi: -0.4 lbs, empty: -0.2 lbs.

 

[kelemvor]

Personally, the first time I dived with it I wouldn't change anything. After that, dial it in.

R..

I just recently started diving with a pony. I normally dive with a heavy LP108, and I didn't change anything for my little aluminum 13 cubic foot pony. I tried converting that to metric, but came up with like 3,000 liters so methinks I did it wrong, sorry.

 

[Bob DBF]

I just recently started diving with a pony. I normally dive with a heavy LP108, and I didn't change anything for my little aluminum 13 cubic foot pony. I tried converting that to metric, but came up with like 3,000 liters so methinks I did it wrong, sorry.

13 cuft is 368 liters. But divers using metric use the actual internal volume of the cylinder itself for computations, not the amount that can be held at pressure.


Since my 19 cuft bottle is about neutral empty, I don't change my weight. If I was carrying a bottle that was positively buoyant I would add the weight needed to be neutral at the end of a dive with an empty bottle. No sense showing up with plenty of air for emergency deco and not being able to hold the stop.


Bob

 

[TMHeimer]

My 13cf pony attached to tank doesn't change my buoyancy either. At least not that I notice.