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On Tue, 4 Oct 1994, David Story wrote:

> Jody Svendsen writes:
> > 
> > My personal theory is two fold.  First, the SEA second stage has a
> > particularly large air space, leaving lots of exhaled gas inside the
> > regulator.  Second, the SEA has a little hole through which fresh air is
[snip]

> All of this is interesting, but I have a strong feeling that anyone
> with a background in fluid flow would discard any such arguments.  You

I don't care what someone's sheepskin says, this is what happens:

1. At depth > 165ft. breathing from USD 2nd Stage you get headaches and 
narcosis doing the normal wreck diving sort of things (just swimming around!)

2. Switch to a Mares Mk-12 or a Posiden, headache & narcosis go away. 

3. Switch back to USD, headache comes back, diver tries to remember 
something about narcosis lecture or something.

I have known about 6 experienced divers who were all good breathers come 
to the same conclusion. Jody took the longest to convince, he is a 
stuborn bastard.

Now if "anyone with a background in fluid flow" would like to accompany 
me while I demonstrate some practical application in fluid flow at 180ft 
on air, I would be honored. If the remain unconvinced after that episode, 
I would demonstrate further applications of fluid flow in a aerobatic 
biplane and get him airsick enough to recant _any_ position the might 
adhere to.

> This discussion is fun, but none of this is provable.  I don't think
> we can reasonably point the finger at dead air space in second stages.

maybe not "dead-air", but there IS something about the geometery of the 
USD second stage that causes these symptoms. The USD and Mares second 
stages demand valves and associated plumbing are identical (the 
replacement parts are interchangeable!). The Mares regulators breathe 
like champs and the USD make u feel uh lifftle fuzzie sumtimess. The 
difference is in the shape of the second stage.



dan@sh*.ne*							mig@shadow.net
Murphy's laws of combat #38:
			"Tracers work both ways."

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