Ignore the tank specs on the web - they're wrong. When I got my dual 104s I
took them into the pool and measured their buoyancy - the bare duals (with
manifold and bands) with 200psi in them were -15lbs buoyant. The full rig
(SS backplate, wing, regs, Pro-4 canister light) was -20lbs at 200psi.

That's in fresh water so they'll be slightly less negative in seawater
(multiply the numbers by 62.4 / 64). I measured the buoyancy by hanging them
from a lift bag, marking the water line on the bag, and then removing them
and hanging a bag of lead in their place and seeing how much lead was needed
to bring the water line to the same level.

By the way, simple physics means that you're going to be lighter climbing up
the ladder in HP tanks because the same amount of gas displaces less water
when its compressed more, so your overall weighting will be less. But that's
a very minor plus compared to everything else where the 104s win out.

Ian

> -----Original Message-----
> From: Steve [mailto:sfkenney@ea*.ne*]
> Sent: Sunday, August 05, 2001 7:28 AM
> To: Jim Cobb; Daniel Smith; techdiver@aquanaut.com; dlhedrick@pb*.co*
> Subject: Re: tanks
>
>
> Jim, I went to the source of tanks for my info. The Pressed Steel Co.
>
> http://www.pstscuba.com/aapro.htm
>
> I was wrong the HP100 is more negative than the LP104 when empty. -1.4
> compared to -.7 pounds, the HP120 is -.4
>
> As far as rust goes I believe that depends on who fills the tank
> and whether
> their are pumping dry air or not. Mine hasn't had any rust in the
> six years
> and it passed hydro.
>
> Steve
> ps: I'm not a tech diver but I'm studying tank spec's making plans.


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