On 26 Jun 2003 at 15:38, Lee Bell wrote:

> Mike Wallace wrote:
>
> > > > He also carried a six liter deco cylinder with  100  BAR of pure
> > > > oxygen.
>
> > > This sounds like a somewhat limited supply.  I seem to recall
> > > being told that most divers use a 50 bar reserve.   Am I correct?
>
> > It's about 1/2 an 80. Plenty of gas for deco even with a reserve.
>
> I went back and looked at this.  6 liters is approximately .21 cubic
> feet internal volume.  At 100 bar, that's roughly about 21 cubic feet
> of gas. The normal U.S. charter operator requests guests to begin
> their ascent from a no deco dive with about 700 psi or, about 20 cubic
> feet of gas and reach the surface with 500 psi or about 13 cubic feet.
>  6 liters at 100 bar is beginning to sound kind of small.  Taking it a
> step further, when gestimating gas needs, I usually plan on a SAC of
> about .5 cubic feet per minute.  My actually consumption is a lot
> lower than that, but I plan for a crisis, not the for the norm.  6
> meters is about 1.6 ata, yielding consumption of .8 cubic feet per
> minute and, with 21 cubic feet,  about 26 minutes to empty.  That
> still sounds a bit thin, but I  no longer have quick access to the
> profile.  I'll go back and look in a minute.  At any rate, it appears
> that whatever gas he had, it wasn't enough.

I typically use a 30 filled to about 2k for a weekend of diving. If I'm using 50/50 too, I'll
have a 40 of it at 3k. Haven't emptied them yet. Get bored hangin' out that long.


>
> > > There's something unexplained here.  At 1715, the diver was in
> > > sight of a boat assigned specifically to him and him alone.  15
> > > minutes later, the diver could not be found.  Since bubbles have
> > > been mentioned, I assume the Dolphin is a semi closed rebreather.
>
> > It is semi closed, but a motionless diver at 6m would produce very
> > little bubbling and the bubbles would be very small. Could be very
> > hard to see them from the surface. But at this point he was on open
> > curcuit deco gas!
>
> Not only that, we're talking about a boat that had already sighted him
> and was there specifically for him and nobody but him.  Somebody
> wasn't paying attention to their job.

Agree, they were SUPPOSED to be watchin' him already. They could have stayed
nearly on top of him and watched.


>
> > He obviously had problems cutting himself loose. I might do it (tie
> > off)
> if I
> > had an in water, same location buddy present but that would be the
> > only way.
>
> Your statement surprises me.  As I recall, you were part of the
> previous discussion of a fire rescue diver who died in training in
> Indiana about a year ago.

Yep, well familiar with that incident. Still bothers me.
As for me tying off, probably should have said clip off at best. I often use a safety
spool as a "jon" line in the ocean, more for comfort than anything else. Were I to use
it by tying it off on the bottom such as this guy apparently did, I would not then tie it to
me. Would probably wrap the line on the bottom and then hang onto the spool. If I
fell asleep in this fashion, I'd just drop the spool and off I'd go. Done it using it as a
Jon line. Interesting feeling. :-)





 As it happens, some of his fellow divers
> are part of my annual spearfishing trip, so I got a bit of inside
> information.  I forget just what the drill was, but it involved a
> heavy weight on the bottom and, perhaps, something located nearby.

Pivot search. He still should not have tied himself into the pivot weight.



 At
> any rate, as I recall the story, the victim tied himself off to the
> weight, exhausted his available gas and headed for the surface only to
> find he was still attached to the weight.  Possibly like Deki, he
> found he did not have time to resolve his problem.  A good diver and a
> good person, gone for no good reason.


Agreed.
>
> I want to keep you around for a while.  Please resist the temptation
> to tie yourself to the bottom when you can avoid it and, if you must
> tie off, please, please be careful.

Thanks... see above.  ;-)


>
> > Possibly but I don't think so in this case. He used, completely, two
> > cylinders of open circuit gas, in addition to the breather's suppy
> > gas. Although I think in this case the breather gas was lost because
> > he failed to turn off the bottle when he went to his deco gas.
>
> Perhaps the sleep idea is a bit thin.  Still, the depth profile at the
> end of the dive is sounds suspiciously like somebody rising and
> falling as they breathe.  I've napped during safety stops myself.
> It's not a real good practice, but it's also pretty easy to do.

Or someone that has/is becoming unconcious from lack of O2 due to no dilutent in
his breather.


--
Mike Wallace
Huntsville, Alabama