Posted by TDI_2 on May 20, 2002 at 15:36:40:
In Reply to: Guesstimate: 3-5 pounds (nt) posted by Ken Kurtis on May 17, 2002 at 17:36:03:
here is a rough calculation for when you switch from an aluminum 80 to a HP steel 80 ...
buoyancy for Luxfer Alum 78.2
-3.6 lbs full & +2.2 lbs empty
buoyancy for Pressed Steel 80
-5.5 lbs full & -1 lbs empty
Therefore, if you were diving with an AL 80 before and at the end of your dive with only 500 psi in you tank, you were perfectly neutrally buoyant, then the difference at that point between an AL 80 and a steel 80 from the above chart data is about 3 lbs.
Take off any more than 3 lbs and you probably wont be able to hold your 15 fsw safety/deco stop.
Whatever you do, you need to re-test your buoyancy in the ocean at 15 fsw with 500 psi in your tanks again, after making your weight reduction.
Egression from scuba diving should be done in increments of halves [see the current DAN bulletin], with your last stop at 15 fws. You will need to be able to hold these stops, and be neutrally buoyant at the end of your dive, which means, for most folks, when you have 500 psi left in your tank. Thats why.