Re: How do you weight?, the first place to look for a dive instructor

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Posted by Kendall Raine on August 26, 2002 at 11:15:53:

In Reply to: Re: How do you weight? posted by Chris on August 26, 2002 at 10:23:51:

Thanks Chris;

Would you mind checking my figures:

A full 120 will have 10 lbs of air full. If the tank is neutral empty, then it's 10 lbs negative full. If you're basically neutral full at the surface with a 13 lbs weight belt, your wetsuit would need to be about 23 lbs positive at the surface. At 130 feet, the same wetsuit exerts about 1/5 of that buoyancy (4.5-5.0 lbs). Assuming a steel 120 is neutral empty, that means you could be as negative as (10+13)-5=17 lbs. Also, if that tank were empty (200-300 psi) at the end of the dive, you would be about 10 lbs positive at the surface, or about 7.5 lbs positive at 15 feet (hence the need to pick up a rock). Obviously this doesn't adjust for the other factors like lung volume and other equipment, and clearly a tank isn't "full" at depth so the degree of net negative buoyancy will decline due to consumption.

With that said, did I get the proportions about right?

My point is to try and quantify why this system is not for beginners.

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