Posted by Northcoast_diver on October 25, 2004 at 11:27:20:
In Reply to: Why 34 lbs? posted by Chris on October 23, 2004 at 20:47:57:
Air weights 0.08 lbs per cu ft.
80 cu ft of air weighs 6.4 lbs.
160 cu ft (twin 80s) weighs 12.8 lbs.
200 cu ft (twin 100s) weighs 16 lbs.
300 cu ft (twin 150s) weighs 24 lbs.
Helium is a little bit lighter than air.
If you do the math, those are the maximum ditchable weights that you would need at the beginning of a dive, whether you are diving with aluminum or steel, and therefore the minimum lift that you would need in a wing or B/C.
I do not personally recommend a lift capacity less than what is needed to float your gear independently of yourself. I like to ditch my gear at the surface before climbing back into a RIB, and therefore my gear needs to be able to float, on its own.