Dave wrote:
On Thu, 27 Apr 2006 15:12:09 GMT, "MMC" said:

Well Dave, in Navy diving ops there is a "standby diver" who in hardhat
diving is completely dressed with exception of the helmet, which takes all
of, let's say 5 seconds to don.

Please don't try to explain to me how the Navy conduct diving ops. I
spent 3
years as a diver and diving officer on a ship where that was a primary
mission. Unfortunately your incomplete knowledge is showing. How does
this
second diver get down to the first diver? Do you think he simply gets
up an
jumps in after the helmet is secured? I don't think so.

Hi MMC:
Had to chime in with the non-union, pot smoking, rat divers approcah.
Uhh jump righ in........... yep. The tender better have a bunch of hose
in the water first.


The stay time may have been longer if the suit were fully inflated. Anyone
that has dove the Mk 5 can tell you that if the suit (or any dry suit with
an air fill) is fully inflated, the diver will be wriggling around on the
surface bobbing like a cork.

I have dived in that suit. While the suit would virtually never be
fully
inflated absent unusual circumstances, it is nearly always partially
inflated. The point is that there's far more air in the suit than just
what's in the helmet.

MMC, I concure. I would like to add, "....if the suit were fully
inflated..." as Dave says I think you Navy guys working the Standard
Navy deep Sea Dress Mod. 1 Mark V would call it an "uncontrolled
assent."


The o2 starts at 21% and when it drops to 16% the diver starts to experience
hypercapnia AND hypoxia.

Wrong except when you're at the surface. It's the partial pressure of the O2
that counts, not the percentage, and that partial pressure increases with
depth. In fact at sufficient depth a 16% heo2 mix could allow one to survive
breathing the mixture virtually indefinitely without such effects.

MMC, Agreed, again....... in the gulf we were using the same % bottom
mix for just about eveything under 420' if I remeber right. But could
be wrong. When I was a green tender I asked why use a standard botom
mix for such a large depth range. He said for simplicity. Did not want
a shop full of diffrent bottom mixes.

When you were doing gas jumps in the Navy did you calculate PPO2 and
mix specific bottom gas for each job? Or just use the "good enough"
approach?

Not all that Salty, Bob