Stage bottles

[Scuba446]

Can someone give me an instance in where and how STAGE bottles are used?

I am a new OW diver and am interested (eventually) in deeper wreck diving.

At what depth(s) and conditions would one need to warrant a 40 cu in stage bottle?

[Scubaroo]

A 40 cu inch stage bottle? :) Spare Air isn't a stage bottle! :D (I know, it was a typo).

Stage cylinders are for extended diving - 80cf aluminum tanks are a popular choice. A diver would use stage cylinders in conjunction with back mounted double tanks, often breathing the gas in the stages before breathing the gas on their back. Think long cave penetrations with scooters, or deep extended dives.

40 cubic foot cylinders (which I guess is what you mean :) ) are more commonly used as deco bottles, holding generally nitrox, or two, holding nitrox and oxygen. EAN50 is a common deco mix, EAN80 has also been used extensively. And of course some people use them as bailout or pony bottles.

[Scuba446]

Yes,
My LDS that has a GUE/DIR Instructor said to get a 40 cu in bottle instead of any pony's..

[WreckWriter]

The terms stage bottle and deco bottle are often, although technically incorrectly, used interchangably. I call my deco bottles stages as do most folks I know. Ben is right about the terms though, his description of a "stage" is the most proper.

40 cf is the correct size for most uses. If carrying only one it should be 100% O2, if carrying 2, they should be 100% and 50%.

I personally carry at least one on any deco dive, 2 on serious dives although carrying 2 is a PITA.

With all that said the use of stages and/or of O2/50% require additional training beyond recreational training. There's a distinct possiblity of killing yourself if you breath O2 or 50% at too great a depth.

If you feel you need a "pony bottle" I still recommend the aluminum 40 (Luxfer version) , stage rigged, not attached to your back, but filled with the same gas as your main tank(s).

Tom

[MikeS]

Originally posted by WreckWriter
If you feel you need a "pony bottle" I still recommend the aluminum 40 (Luxfer version) , stage rigged, not attached to your back, but filled with the same gas as your main tank(s).

Tom

Tom,

What is the reasoning behind a 40 cf pony? Is such a pony to be used as additional air or a bailout? Keeping in mind that additional mass requires more effort to move, isn't 40 cf excessive for a bailout?

Here is the calculation that I came up with base on no overhead dives to no greater than 100 fsw..

Problem occurs:

2 minutes at 99 fsw to sort out problem with surface rate of 1.2 cfm = 9.6 cubic feet
Ascent from 99 fsw to 15 fsw at 30 ft/min with surface rate of 1 cfm = 7.6 cubic feet
3 min Safety stop 15 fsw with surface rate of 1 cfm = 4.4 cubic feet
Ascent to surface from 15 fsw at 30 ft/min with surface rate of 1 cfm = 22.2 cubic feet

The surface air consumption rates are probably conservative since my dives have been averaging a surface equivalent rate of 0.6 cfm, but there is potentially a high level of stress based on the fact that a problem exists resulting in the need for a bailout bottle.

The one thing that the calculation clearly shows is that a 3.0 cf Spare Air is a waste of money and potentially dangerous in that it promotes a false sense of security.

Any insight would be appreciated.

Mike

[WreckWriter]

Originally posted by MikeS

Tom,
What is the reasoning behind a 40 cf pony? Is such a pony to be used as additional air or a bailout? Keeping in mind that additional mass requires more effort to move, isn't 40 cf excessive for a bailout?

A pony is for bailout. I don't personally like them, I prefer doubles with an isolation manifold but IF one must use a pony....

My primary reasoning is to get a bottle which will continue to be useful when/if the diver progresses to technical diving. Also, that extra gas might save your buddy's life.

Actually, when rigged correctly, a 40 cf stage produces very little drag, much less than a smaller pony tank mounted would produce.

Yes, spare air is useless.

Tom

[roakey]

Originally posted by MikeS
What is the reasoning behind a 40 cf pony? Is such a pony to be used as additional air or a bailout? Keeping in mind that additional mass requires more effort to move, isn't 40 cf excessive for a bailout?
Neither, let me restate what bengiddins and WW have said.

We have a tendency to use term “stage” incorrectly so let me be formal for the rest of this note...

A 40cf makes an excellent DECO bottle. For either pure O2 or in some cases (read: ocean) even for 50/50 because your gas consumption is low given the shallow depth.

A STAGE bottle is used for extending your dive, so I can’t think of any reason that you’d want a stage smaller than an AL80, why bother? Traditionally in caving you’d breathe a stage to 1/2 - 500, drop it, breathe the next stage to the same point, drop it, go to your back gas, breathe 1/3, turn the dive. On the way out you’d pick up the second stage you dropped and start breathing that, then the first stage and then you’re out.

Nowadays it sounds like the WKPP is starting to dive stages only and saving their back gas for emergencies.

You’re right, a 40 may be too big for a pony, but if you think that someday you might see the light :) go with a 40 cf pony and later you can turn it into your O2 or 50/50 bottle without further investment.

Roak

[MikeFerrara]

1/2 - 500?

[VTWarrenG]

He means "between one half of the tank's starting pressure and 500 psi"

- Warren

[Scuba446]

I was thinking of going with a 40 and using it as a pony for now, sicne non of us dive twins or H-valves - and it might be good medicine for shipwrecks deeper than 60 ft, but not more than 100 ft.

[Scubaroo]

I read it as "1/2 of the tanks starting pressure, MINUS 500", eg for a 3000psi tank, 1500 - 500 = 1000psi. But I'm not sure if that means you only breath 1000psi out of 3000, or leave 1000psi out of 3000?

Roakey! Explain yourself!

[MikeS]

Breath to 1750 and drop ((3000-500)/2=1250)?

[roakey]

Originally posted by MikeS
Breath to 1750 and drop ((3000-500)/2=1250)?
We have a winner!

Sorry folks, I didn't mean to gloss over that.

Roak

[VTWarrenG]

Oops.

Yes, color me stupid.

- Warren

[MikeFerrara]

Ahhhh like 1/2 + 250

Why not use thirds?

[Divesherpa]

I was unaware that GUE taught stage diving in Cave 1.
This is a blatant 1/3's violation.

[roakey]

Originally posted by Divesherpa
I was unaware that GUE taught stage diving in Cave 1.
This is a blatant 1/3's violation.
Looks like a trap to me, let's see if I can avoid it.

They don't. I dive stages elsewhere.

Why do you consider stages a blatant 1/3 violation?

Roak

[Divesherpa]

reason for rule of 1/3's is to ALWAYS have twice the gas needed to egress so that if you have a failure you will be safe.
Is the 1/2 - 500 psi really the DIR rule of stage diving? Sounds like unnecessary risk to me. What GUE class is this taught in?

[roakey]

Note my use of the word "traditional." No, by my understanding this is not what's taught in Cave II, but ask me again in October.

I *think* that GUE/WKPP teaches 1/2-500 but you don't touch your back gas except in an emergency. Perhaps someone can tell us if that's right or wrong.

Roak

[MikeFerrara]

I thought I read somewhere 1/2 + 200 almost the same. I use thirds max (more gas is better). The most I've used is two stages and then often it's to save more back gas for another dive. Obviously I'm not going 20,000 ft. If someone has another methode I would be interested in seeing the numbers and hearing the theory.

[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]

[QUOTE]Originally posted by roakey
[B]
"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%.