Cave 1 single tank restriction scares me...

[nimoh]

Ok, let's take a look at something:

Situation 1:
Kotik and his bride are diving a no-flow system. She is wearing a single HP 120. He is wearing two HP100's. All tanks are filled to their rated capacity. Both divers have exactly the same air consumption. They are diving to 1/3rd's
As they hit turn pressure and turn around, it triggers a freeflow in her regulator, which evacuates the entire remaining tank contents in 1.5 minutes. Each diver has used 40ft^3 at this point, so Kotik has 160 ft^3 to divide up between them for the exit. So each diver now has 80ft^3 of gas to make the exit, twice as much as what they needed to travel that distance going in.

Situation 2:
James and AJ are diving identical circumstances, except both divers are equipped with double 120's. This time it's the isolator valve that lets go at turnaround. Each diver has used 80ft^3 at this point, so one diver has 160 ft^3 to divide up between them for the exit. So each diver now has 80ft^3 of gas to make the exit, exactly the amount required to get back, hope nobody's air consumption goes up.

I'm convinced. You guys should be diving 1/6ths.

Any number of scenarios can be dreamed up to prove a point you want to make. IMHO, the relative probability of the scenario and the vehemence put into making the case for it should be somewhat proportional, and sweeping loaded statements about what the world should do should be used pretty sparingly in general. That's all I'm sayin'

not sure I follow your point. In situation 1 if Kotik had lost all his gas, they would be in the same situation with 80ft3 to share.

 

[LiteHedded]

He's only been cave diving since 2012 cut him some slack. Some ppl are slow learners

 

[kotik]

You've just figured out why thirds in a no flow cave is a somewhat aggressive gas plan.

It's an assumption on your part that I've just figured this out. My point is, a lot of the heat in arguments given seem to assume incompetence. Anyway, you guys are the divers, you're the one's who figured it out.

---------- Post added September 12th, 2013 at 02:16 PM ----------

not sure I follow your point. In situation 1 if Kotik had lost all his gas, they would be in the same situation with 80ft3 to share.

Kotik's gas supply is independent, he is fairly immune to losing it all.

 

[nimoh]

incidentally, GUE has recently moved away from rule of sixths for Cave 1.

The new rule is 1/3 of 2/3. Using this approach, I would take out 2/3 for reserve and use 1/3 of that for penetration. It is a little less conservative than sixths, but more conservative than thirds.

 

[PfcAJ]

Well, an intro diver generally isn't drawing on years of cave diving experience in varying conditions...

 

[LiteHedded]

ignoring this fantasy land scenario. how about the more likely one.
you are blitzed out and lost. which diver has more gas to solve problems? TRUST me when I tell you this sort of thing is really what that gas is for

or you're entangled, or your buddy has toxed or any number of things that can happen (and are more likely to happen than a magic exploding gas supply)

 

[kotik]

ignoring this fantasy land scenario. how about the more likely one.
you are blitzed out and lost. which diver has more gas to solve problems? TRUST me when I tell you this sort of thing is really what that gas is for

or you're entangled, or your buddy has toxed or any number of things that can happen (and are more likely to happen than a magic exploding gas supply)

Other than the magic instantaneous loss of gas, and that sometimes I'm diving 130's instead of the smaller tanks, situation one above is exactly how it goes down when we dive together. I am quite comfortable with the level of conservatism on these dives. There's nothing about our conduct of them that puts us at greater risk from the problems you mention than two divers in doubles diving thirds would generally assume. In truth we have a lot bigger ratio of reserve gas than most pairs would have diving 1/3rds, even if they're adding extra reserve in deference to low flow.

 

[PfcAJ]

Except the divers who are taking doubles to thirds are fully qualified. That's a big deal.

 

[kotik]

Except the divers who are taking doubles to thirds are fully qualified. That's a big deal.

She's diving within the limits of her certification, which she earned honestly I happen to know. What exactly do you know about her that you see fit to pass judgement that she's unqualified?

 

[PfcAJ]

Is she a fully qualified cave diver? Or does she hold an introductory certification? Introductory...