Posted by MHK on October 02, 2000 at 09:33:15:
Earlier last weel you once again challenged something that I said, and as usual you were once again wrong. You bet me $20 that compressed neoprene drysuits do not compress at depth as I had suggested. Please send my winnings to ths Catalina Hyperbaric chamber and please check your facts before you attempt to correct me in the future because this game of * I gotcha * is getting very tiresome on this list and it laways turns out that you are wrong...
As I told you earlier last week the WKPP guys had commisioned a studt to studt the effects of drysuit compression at depth. Bruce Wienke, who is the Director of the Computational Testbed For Industry in the Advanced Computing Laboratory of the Los Alamos National Labroratory. He has a PhD in physics from Northwestern University and is a memeber of the American Physical Society, American Nuclear Society, Society of Indisturial and Applied Mathematics, Undersea and Hyperbaric Medical Society. He is also an IT with NAUI serving on the Decompression Review Board, a Master Instructor with PADI, serving on the Instructor review committee and an Institute Dorector with the YMCA. He is widely regarded as the foremost authority on decompression algorithms, diving physics and if this isn't good enough for you there isn't much more I can do to help you.
Weinke wrote:
Gas bubbles in westsuits and compresed drysuits are subject to Boyle's law as external pressure changes, though the response is something less than 50% of the volume change predicted by the gas law. To estimate the bouyancy increase due to expansion or compression, we compute the effect using Archimede's principle and Boyle's law directly, and then scale the result by the factor 0.50, as a figure of merit. Denoting the volume of the wetsuit or compressed drysuit on the surface as U, and the corresponding volume at ambient pressure, P, as V, have by the gas law.
P v = P s u
With P s, surface ambient pressure. The theoretical buoyancy change, Change ( insert triangle symbol ) w, relative to surface buoyancy, is given by,
Change w = p(v-u)
with P the actual water density. Using the above gas law, it follows that,
Change w = pu ( ps - 1)
-------
P
Making teh assumption that the drysuit or wetsuit offsets the weightbelt at the surface some fraction, f, of the diver's body weight, w
pv0 = fw
where,
0.10 +/- f =/-0.20
as a rough figure of merit
At depth, the bouyancy LOSS ( pay attention here EINS ) can be written
Change ( insert Triangle ) w = .50 f w ( ph
------ - 1 )
while at greater depths, with d * 33 fsw, the loss is roughly connstant at
w = .075 w.
So you now awe me two things if you trust Bruce Weinke
1) you owe me an apology
2) Send $20 to teh Cataline Hyperbaric Chamber
and then I'll ask that before you attempt to correct me again you remember that you somehow have lost all credibilty and it is getting old and tired..
Later
ph + nd