Posted by Ed on July 12, 2002 at 11:27:41:
In Reply to: Re: adjusting ocean weighting to freshwater weighting? posted by Neil on July 11, 2002 at 23:32:54:
This was mentioned earlier(slob vs. Fabio), but here is another angle.
The absolute weight of the diver/gear/etc mean very little. If you had 2 solid balls of metal, one made of Aluminum, the other out of Lead, each weighing 100 lbs. on the scale, you would need a LOT more 'bouyancy' to make the Lead 'neutraly buoyant'. The 100lb Alum. ball will have a greater 'volume' to it, thus it displaces more water.
To make things a bit more interesting, let's consider this: The 100 lb. Aluminum ball will surely 'sink'. However, take that SAME Aluminum ball, melt it down, make a thin walled hollow ball out of it.... It still weighs 100 lbs on the scale, but it will float like a buoy!
Sorry to go off on a tangent.... Roughly speaking, you can calculate for the compensation needed for fresh vs. saltwater in RELATIVE terms only... 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. However, in my opinion, it is much better to determine this imperically, as one's buoysancy changes daily, as your weight/volume will also fluctuate on daily basis.
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