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I recently found this tech diver list.  Man you guys are mean!!!!  All this
talk is about diving ?  There MUST be a WOMEN involved somewhere to generate
this type of animosity. ANYWAY..

My post is about Gas matching as presented in the IANTD Deep Air Text.  The
book describes a method of calculating the required adjustment to the rule of
thirds for a penetration dive for a pair of two divers.  The IANTD solution
involves working through a series of tables to determine the "turn pressures"
for the divers.  

I attempted to verify and regenerate the tables using a spreadsheet and found
that the solution presented by IANTD in the Deep Air Text is not correct.  

The error in the solution is that sometimes the answer is correct and
sometimes it is around 15% conservative depending on the relative tank volumes
and RMV's of the individual divers.  The diver using the IANTD tables seems to
have no way of determining when the solution is exact (i.e. no magin for
error) and when it is conservative. 

I have written a simple spreadsheet solution to get the answer correct.  It
would seem that a diver using this technique could add a known safety factor
rather than an unknown or non-existant one as is supplied by IANTD.  

I have provided documentation of the problem to Tom Mount and IANTD quite a
while ago and have received no response.

Does anyone really use the IANTD method?  Does anyone want to do it correctly
with a spreadsheet?  Is this just petty BS that the experts know about
already?

Jim Fyfe



Jim Fyfe
--
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