Stages: 1/2+200 or 1/3rds

[SuPrBuGmAn]

Sometimes size constraints won't allow for the extra gear, ditching it early just makes sense or you find yourself really messy. Sometimes thats even before 1/3rds. *shrugs*

If the plan doesn't necessarily call for a ton of gas, calculating 1/3rds off a stage is easier...



Ninja edit: thanks for the added option!

 

[rjack321]

Why just go out of gas once? If you share stages you get to go OOA multiple times and it just makes the dive all around more interesting

Man that was the BEST DIVE EVER!!! We SURVIVED wooo hoo!

 

[LiteHedded]

Why just go out of gas once? If you share stages you get to go OOA multiple times and it just makes the dive all around more interesting

well that's certainly one approach

 

[UCFKnightDiver]

Just for kicks, and keep in mind I don't stage dive yet, but are there any pro's/con's for breathing down a stage completely and then saving it in backgas?

The only two cons I can think of is you're putting all your eggs in one basket, though you do have your buddy's gas, so not really and you would want to drop the stage sooner rather than swim it all that way.

 

[Cave Diver]

Is there some different logic going on behind the scenes here than 1/3rds of backgas & 1/3rds of stages? Some CCR or bailout issue?

Sorry, that should have read 1/3 not 2/3's. This was for OC dives, not CCR.

I was told to leave 1/2 + 500. Which on a 3000 psi tank means you breathe 1/3 and leaves 2/3 of the gas remaining when you drop it. The logic was that you slightly reduce the distance you've penetrated on +500 vs +200, you have a buffer in the (unlikely) event of a gauge error and you have more reserve available in your stage in case of a problem during the dive.

Effectively it's the same as being taught to dive 1/3 of stages, it was just presented differently.

 

[Cave Diver]

Just for kicks, and keep in mind I don't stage dive yet, but are there any pro's/con's for breathing down a stage completely and then saving it in backgas?

The only two cons I can think of is you're putting all your eggs in one basket, though you do have your buddy's gas, so not really and you would want to drop the stage sooner rather than swim it all that way.

Ability to pass off a stage in an OOA emergency would be one con to breathing it down. I'd rather not have someone on my long hose if I have an option to pass a bottle off.

 

[SuPrBuGmAn]

Just for kicks, and keep in mind I don't stage dive yet, but are there any pro's/con's for breathing down a stage completely and then saving it in backgas?

The only two cons I can think of is you're putting all your eggs in one basket, though you do have your buddy's gas, so not really and you would want to drop the stage sooner rather than swim it all that way.

Like 80cf in and keeping an additional 160cf for the return? You'd have to contend with a stage with nasty bouyancy for alot longer...

I suppose you could argue that you'd find an issue with your other regulators by moving to them sooner, rather than later? A flimsy arguement at best.

 

[rjack321]

Just for kicks, and keep in mind I don't stage dive yet, but are there any pro's/con's for breathing down a stage completely and then saving it in backgas?

This is what we do in OW. Kill the stage then switch to backgas. Rotate the empty back on the leash. There's no place to drop it and I am not giving an OOG diver 1/2 or even 2/3rds of a stage, they'll probably just go OOG on me again mid-ascent. Not to mention they have no power inflator and probably need "help" close at hand for the next issue to arise.

In wrecks, sometimes diving AL80 doubles, I have done 1/2 in on the stage and 1/2 out leaving the whole doubles as reserve (effectively 1/6ths). If the wreck isn't too deep (<100ft) I can do this just within "no deco" limits. For another dive I swap out the stage with a fresh one and I'm good to go.

 

[PfcAJ]

Lets run a scenario where we are doing a double stage swim with 104s for backgas. Max allowable gas for penetration is 1/3 of 442 cuft (77+77+288), or 147cuft.

The first stage is dropped at half+200psi (32.5cuft ), same with the 2nd stage (another 32.5cuft). 3600psi/3 = 1200psi. Subtract 100psi per stage, and we now have 1000psi (80cuft) available for penetration. Total usable is 145cuft. Still within thirds, but...

This places your reserve gas in a format that is easily shared (longhose), with you (able to be shut down, isolated, etc) and not turned off, as most failures occur on re-pressurization of the stage reg. If you really need that gas, the last thing you want to deal with us a fubar'd reg.

If diving 1/3 of stages and you do happen to exhaust your backgas when you hit your bottle cache', pick up the stages (one for you one for your buddy), by the time you get back to the 2nd cache', you have 1/3 of a stage bottle locked up in a worthless format. It has to be carried (slowing you down), hose stowed (slowing you down) and is unsharable.

Now, things change in deep cave and when scootering. The best (and proven) solution is to dive stages only and save backgas as pure reserve. This works not only for sharing gas, but for delayed exits (poor vis, light failures, etc). If your buddy has a real bad situation and loses a lot of gas, the answer is to get them on the long hose (NOT stage) and tow out. Otherwise, they'll simply run out of gas again, which will put a temporary halt to the exit and they'll have to get on your longhose anyway.

 

[ianr33]

Never done a stage course so I had to learn this from the Internet

1/2 + 200 makes more sense to me.