Stage Diving: What are you doing?

[atedeschi]

Ok so here is what I am going:

Single Stage Dive:
lp85s filled to 3600psi
AL80 filled to 3000psi

Breath stage to 1700psi
Breath 85s to 2600psi then turn dive

If I lost half my gas at max distance in and can still get out and have 7.32 cu ft in reserve.

Double Stage Dive:
lp85s filled to 3600psi
AL80 filled to 3000psi
AL80 filled to 3000psi

Breath stage to 1700psi
Breath stage to 1900psi
Breath lp85s to 2600psi

Still have 3.32 cu ft in reserve if lost half of all my gas at max pen.
This is for a no flow cave, i would make adjustment for things like restrictions, low silty nasty areas, etc. But for normal swimming no flow caves this is the plan. If you look at the total gas avalible and used i still more conservative then 3rds. Now for flow my numbers will be different for the lp85s but if you use this for caves with flow you will be even more conservative with this plan or you could adjust the lp85s to get more out of them and keep the conservatism the same, but thats another beast and could be search in a previous thread.

[rjack]

so in those cases, you take off 400 psi for 1 stage, and just 7.5cft (300 psi in stage and whatever that is in BG) for subsequent stages, if you are OK assuming just one will fail

No I am assuming all the stages are all going to go bye bye for whatever reason. They are not on me so I don't plan on having that gas available on return. I am just a baby cave diver and haven't gotten to the point where the required backgas reserves exceed my backgas capacity (>4 stages with AL80 backgas, >9 stages with 104s).

[atedeschi]

No I am assuming all the stages are all going to go bye bye for whatever reason. They are not on me so I don't plan on having that gas available on return. I am just a baby cave diver and haven't gotten to the point where the required backgas reserves exceed my backgas capacity (>4 stages with AL80 backgas, >9 stages with 104s).

after 2 stages its not worth the effort swimming and gas usage, a scooter would be involed then the planing is a different ball game.

[rjack]

Ok so here is what I am going:

Single Stage Dive:
lp85s filled to 3600psi
AL80 filled to 3000psi

Breath stage to 1700psi
Breath 85s to 2600psi then turn dive

agree, 600psi reserved in lp85s covers loss of the stage.
32cf used from the stage, 6*6cf = 36cf extra reserved in backgas

Double Stage Dive:
lp85s filled to 3600psi
AL80 filled to 3000psi
AL80 filled to 3000psi

Breath stage to 1700psi
Breath stage to 1900psi
Breath lp85s to 2600psi

I would breath both stages to 1700 but turn on backgas at 2800 (thirds of usable)

[rjack]

after 2 stages its not worth the effort swimming and gas usage, a scooter would be involed then the planing is a different ball game.

oh I realize that, I have swum 2 stages a few times and its a pita. just illustrating where the logic eventually takes you. to not touching backgas at all and eventually adding safeties.

[aainslie]

So it seems a common approach is to breathe the stage below 2/3 BUT reserve the extra in BG. I like it. Couple of questions:

Is this an official GUE and/or UTD approach? Does anyone else officially teach this?

Why do that rather than just go to 1/3 and then carry a bit further? Woudln't it make for identical redundancy plus easier planning?

[atedeschi]

I like having the extra with me, because maybe I need it after I drop the stage or if the stage bottle is gone, empty (not likely), or some other reason, I can use it up and dump it on the way out if needed. I also carry a wrist slate for deco, making notes for flow and Sac calculations and wear jumps and features are at, so I can add to the maps. So if I have multiple bottles with different drop pressures I right that on there as well.

[LiteHedded]

So it seems a common approach is to breathe the stage below 2/3 BUT reserve the extra in BG. I like it. Couple of questions:

Is this an official GUE and/or UTD approach? Does anyone else officially teach this?

Why do that rather than just go to 1/3 and then carry a bit further? Woudln't it make for identical redundancy plus easier planning?

I know it's what GUE teaches but I'm not sure about UTD. I would assume it's the same.
I like having that reserve on my back where I have more flexibility with it.
the planning is pretty easy with 104/108s/130s. it works out to about 100 psi off your backgas thirds (per stage) to keep yourself under total thirds.
so half+200 on the stage and 1100 instead of 1200 for backgas penetration gas. of course, you're free to get more conservative from there. but I like to keep that gas on my back and not in the stage(s).

[aainslie]

I understand why you want to carry it with you. But then if you lose 1/2 your BG, you lose 1/2 the "reserve" from the stage that you moved over there. Doesn't that worry you? Doesn't it make more sense to leave it in an independent tank (the stage), and just carry the stage a bit further instead?

The whole point of splitting reserves up is so that the loss of one tank doesn't take a disproportionate percentage of your gas with it.

[Chris Laughrey]

So it seems a common approach is to breathe the stage below 2/3 BUT reserve the extra in BG. I like it. Couple of questions:

Is this an official GUE and/or UTD approach? Does anyone else officially teach this?

Why do that rather than just go to 1/3 and then carry a bit further? Woudln't it make for identical redundancy plus easier planning?
__________________
Andrew Ainslie

GUE teaches it. So does NAUI. The latter (which I teach) actually explores several different stage options. All of these options operate within the rule of thirds, but differ as to how you carry that third. I like the 1/2 plus 200 for dives involving a single stage sand use it up to two. After two stages, it starts to get silly subtracting the stages third volume from your back gas before calculating thirds for the latter. Also, I don't have any reason to swim that far anymore. I'm too busy here at work to start down other the road with other options, but I approach managing thirds on the DPV in an entirely different way. For example, it sometimes works out to kick the stages and leave the back gas alone and completely dedicated to contingencies. And there are other ways to approach it, but ALWAYS within thirds at the least. Planning always includes all the what ifs and calculations of swimming distances/times. I know you are a NAUI instructor so look at the article on 1/2 plus 200 in the latest Sources. Distance and time are included in the worst case scenarios there.

Chris