Sorry Ed, but that is BS

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Posted by Eins on July 12, 2002 at 11:47:12:

In Reply to: Diver's weight is NOT the issue.... posted by Ed on July 12, 2002 at 11:27:41:

Your metal ball analogy is irrelevant. We are talking about a diver.
Then you wrote:
If the diver (regardless of his weight, or the gear, given that he will use the same) required 30 lbs. of weight to be neutrally buoyant in saltwater, he would roughly need 30/(1.025) = 29 lbs. in fresh.

That is BS! The weight belt is not the target to adjust for, the target is to maintain neutral buoyancy of a system, and this system is the entire diver, not just his weight belt. The weight belt is never neutrally buoyant with 30lbs. Think about it!

The diver displaces a certain amount of salt water. This is a result of his weight and his volume. Since, on humans, the deviation is not that great and the compensation factor is only quite small, we can neglect the precise approach to measure water displacement but go with easily measurable (dry!) weight of the fully equipped diver instead. Subtract 2.5% to adjust for fresh or add 2.5% to adjust for salt water. It IS that simple.

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