Stage bottles

[Divesherpa]

As for stage diving, I stage about 4 dives per week. I never break 1/3's on any cylinder (except deco cylinders). If DIR says break 1/3's, then we have just found a huge flaw in DIR.
I dive with a few of the guys who made this "tradition". They disagree with you on this one and they are where the tradition came from. IF AT ANY POINT OF CAVE PENETRATION YOU HAVE LESS THAN TWICE THE AMOUNT OF GAS YOU NEED FOR EGRESSION, YOU ARE VIOLATING 1/3'S.

Back to the original question: Stages are great ways to extend you dive time and to add safety to a dive, if done properly. Insure that you are trained properly before doing dives of this magnitude. Do not take the advice from some anonymous joe who's unsure about procedures.

And ROAK, good luck in Cave II. If you are taking it in Florida, I may bump in and see how great things are going.

 

[MikeFerrara]

Divesherpa,
There were a bunch of us down there acouple weeks ago. I kind of expected you to come around. Campana was finishing his cave training williama and his other half were there and my wife and I had a week to be cave bumbs. Maybe next time.

 

[Jeff M. English]

GUE surely can't mean turn at 1750 on an AL80 stage?!

ROAK, if you actually meant "turn after you breathed 1/2 of 3000 psi - 500 psi" then I see where the confusion is coming from.

1/2 of 3000 = 1500,

1500 - 500 = 1000,

Turn after 1000psi *is* thirds for an AL80, but I would never state it that way because it's *D@$#ed* misleading.

Jeff

 

[roakey]

Ok folks I had a senior moment. If you use your back gas, you only use 1/3 of each stage and back gas as Dive Sherpa states.

If you don’t use your back gas, the rules change. Dive Sherpa, do you have a problem using 1/2 - 500 (or 300 or 200 or whatever) if you don’t use your back gas?

Roak

Ps. Don't ask me what I was thinking, I don't know.

 

[roakey]

Originally posted by Jeff M. English
GUE surely can't mean turn at 1750 on an AL80 stage?!

Yes, 1750. Reason through it not using your back gas except in case of emergency.

Simple example (I'm actually use 1/2 of each stage to make it worst case and because I'm lazy ):

You make a four AL80-stage dive wearing double 95s that aren't overfilled.

The stage you're breathing fails at the point of furthest penetration.

You've used 160 cf (4 x 40) to make it in that far, and you've got 190cf on your back. In addition you have 190cf on your buddy's back AND chances are that one or more of your stages will work on the way out. ALSO if you have problems with any reg, you can swap them in the water.

It's actually a far more conserative way to dive than 1/3s!

So, you have a choice, 1/3s on everything or 1/2s on stages and don't touch your back gas.

Roak

 

[MikeFerrara]

This subject just came up on the NSS-CDS site. It was explained as 1/2 + (200 + reg IP at depth) with some back gas reserved to back up each stage. 500 psi in double 104's was used but of course this would depend on the size tanks being used. Even with thirds you can't assume that you can use all your gas. You need to use thirds on the usable gas. I would like to hear what the advantages of the above methode are supposed to be.

If one team member lost a stage, you could give him reserve from your back gas while it would be hard to share reserve in a stage. However, with the reserve in the previouse stage he could use the previouse stage. Having some or all of the reserve in the doubles could be good in that you have redundancy there. If you had a problem (worst case) and it took all your back gas to get back to your last stage (using thirds) you would still have double the gas needed to get out but no redundancy. On a single stage dive and 2 divers without back gas you are exiting with one stage each and no redundancy. A second failure could leave you buddy breathing on a single stage. If the reserve was in the back gas all you have is a simple air sharing swim. What are the odds? It does seem that on a stage dive extra reserve back gas is a good idea but..if you try to carry too much gas that you don't intend to use then you defeat the purpose of the stages in the first place.

It just goes to show that if enough things break in a cave you will die.

 

[Divesherpa]

Roak, I'm not sure how that would work. That is above my level of training. It's seems fairly solid. You would have to have a large number of stages to come up with with this technique, with 4 being the very minimum. This would be conservative in this situation, but I think the place where this would become important if far beyond that.
Nice topic for debate.

Mike, I apologize. Next time.

 

[Jeff M. English]

Originally posted by roakey

"Yes, 1750. Reason through it not using your back gas except in case of emergency.

Simple example (I'm actually use 1/2 of each stage to make it worst case and because I'm lazy ):

-SNIP-

It's actually a far more conserative way to dive than 1/3s!

-SNIP-"

I get the idea but I disagree with "far more conservative", by my math I get that as being just a little over 18% "more conservative", or rather you end up with just over 18% more usable gas that way:

What you are, in essence, doing IS diving thirds, you keep one third of your total supply in your doubles, untouched. If you were diving double AL80's and carrying 4 AL80 stages that would be Exactly the case, In your example you get a little more hedge because the backgas is bigger than any two stages.

If you were diving AL100 stages, (not that anyone would), and double 95's with no overfill, and you tried this you would, in fact, violate thirds. This would not be a very conservative (or reasonable) way to dive an overhead. It's a neat idea but as it was stated it makes me skeptical. The take home lesson, as always, would seem to be 'make sure you have twice as much gas, OR more, to make your exit'. No revolutionary idea, just proper prior planning.

Having said that, I do think it sounds like a good plan to have the doubles full up and ready to take you and your buddy that last halfway out, unencumbered, if everything goes to pieces. Good topic and a neat idea , thanks ROAK.

Jeff

P.S. My bad, that's 18% more gas if diving LP95's on the back instead of AL80's. If we actually compare Diving 4XAL80 + 2XLP95 to thirds vs. diving the same setup with the backgas used as our reserve gas we get about 12% more reserve gas from the untoched-backgas option then from the straight thirds option, not 18%.