Steel tanks - what's what...

[rstofer]

So, it's a steel 72. Actually 65 cf at 2250 psi. If the tank is '+' rated, it can be filled to 2475 psi and you will get the nominal 72 cf. Look for a '+' stamped after the most recent hydro stamp.

If you were using Al 80s, it didn't do much for your ballast situation. An Al 80 could be as much as 4# positive at the end of a dive whereas an HP 100 will be 2.5# negative. All else being equal, you need to carry about 7# more lead when you use an Al 80 versus an HP 100.

I have no idea what the buoyancy characteristics are for an LP 72. I have been trying to get the numbers so I can increase the lead in my weight harness. It MIGHT be something like 5# negative when full, neutral when empty. But I'm not sure of tha and I'm not sure that 3# will make a difference. I'm already a little heavy according to DSS.

I get mixed reviews about the buoyancy and trim characteristics of the LP 72. I just want to use it with my Mistral double hose regulator. This particular regulator probably shouldn't see 3000 psi.

Richard

 

[DA Aquamaster]

I have owned maybe 20 steel 72's over the years. They range from 1 pound positive to 1 pound negative when empty depending on who made it and when.

On average, they are about 4 lbs more negative than an AL80.

Personally, I like the buoyancy and trim of steel 72's and they make great recreational doubles.

As a single they are 2 pounds lighter than an AL80 and you can carry 4 lbs less lead so you save 6 pounds in tiotal weight.

 

[halocline]

I dove my double 72s last weekend for the first time. Once I got over the initial adjustment to a lot more mass on my back, I really enjoyed it. They're surprisingly easy to carry on land, and overall I found that I trim out well in them. I think the two big differences from single tank diving for me are the extra inertia and the rec wing. That thing is supposed to be a small doubles wing, to me it was like diving with a life raft. It's nice on the surface, I could inflate it and float on my back all day. I'm used to the immediate venting and precise buoyancy adjustments of a really small singles wing; this ain't it.

I breathed them down to 500 PSI, and still needed no lead with a 5 mil suit, AL plate, fresh water. The bands, manifold, and extra 1st stage probably add 4 lbs minimum.