Cave Deco Dive Planning

[1atm]

So I am going over my elearning for my cave cert, and it briefly talked about gas planning and deco dives.

I think understand the gas planning side of it, you need to plan your dive, get the total gas required from deco and subtract that from your available gas before calculating turn pressures during your dive briefing.

But how does one plan the deco in cave divng? Do I just put each segment in Multideco with the expected transit times as the bottom times? Or is there a better tool?

I’m not so sure on the subtract deco gas strategy ... if the cave allows it I would always prefer to take a dedicated deco bottle that can be dropped. Chances are you don’t have to take it far. (Obviously make sure that there is sufficient redundancy in the team incl the back gas to cover loss of a deco bottle)

 

[rjack321]

I’m not so sure on the subtract deco gas strategy ... if the cave allows it I would always prefer to take a dedicated deco bottle that can be dropped. Chances are you don’t have to take it far. (Obviously make sure that there is sufficient redundancy in the team incl the back gas to cover loss of a deco bottle)

Nobody is doing any significant (>15mins) amount of backgas deco in a cave. If you don't have a deco gas you do need to subtract out some backgas for deco. But 15mins at 20ft is (0.5 * 1.6 * 15 = 12cf or <200psi in a set of 104s and even in lp85s its only 200psi).

An al40 of O2 covers at least an hour of deco in FL caves.

You do have to reserve a little gas for the stops to get up to 20ft if you are in someplace like Ginnie with a 60min deco obligation. Doing 2 hours of backgas deco at 20ft if you lost your deco bottle? That is not taken out of your reserves (in part because it would be 0.5 * 1.6 * 120 = 90+cf). Sharing your buddy's 40cf would be wise and you have at least 1/3rd of your backgas too. To accumulate that much deco you need at least 104s and stage so 363cf /3 = 121cf remaining - look magic you have enough in you 1/3+ remaining to cover at OOA buddy or a lost deco gas (but not both). But you'll probably freeze if you had to hang at 20ft for 2 hours though. Better to split that O2 with your buddy and only hang for ~ 80mins.

 

[1atm]

Nobody is doing any significant (>15mins) amount of backgas deco in a cave. If you don't have a deco gas you do need to subtract out some backgas for deco. But 15mins at 20ft is (0.5 * 1.6 * 15 = 12cf or <200psi in a set of 104s and even in lp85s its only 200psi).

An al40 of O2 covers at least an hour of deco in FL caves.

You do have to reserve a little gas for the stops to get up to 20ft if you are in someplace like Ginnie with a 60min deco obligation. Doing 2 hours of backgas deco at 20ft if you lost your deco bottle? That is not taken out of your reserves (in part because it would be 0.5 * 1.6 * 120 = 90+cf). Sharing your buddy's 40cf would be wise and you have at least 1/3rd of your backgas too. To accumulate that much deco you need at least 104s and stage so 363cf /3 = 121cf remaining - look magic you have enough in you 1/3+ remaining to cover at OOA buddy or a lost deco gas (but not both). But you'll probably freeze if you had to hang at 20ft for 2 hours though. Better to split that O2 with your buddy and only hang for ~ 80mins.

yep, what I meant above. Maybe I misunderstood the OP comment regarding subtracting deco gas from back gas and hence brought this up.

 

[Daedalus]

Sharing your buddy's 40cf would be wise and you have at least 1/3rd of your backgas too. To accumulate that much deco you need at least 104s and stage so 363cf /3 = 121cf remaining - look magic you have enough in you 1/3+ remaining to cover at OOA buddy or a lost deco gas (but not both). But you'll probably freeze if you had to hang at 20ft for 2 hours though. Better to split that O2 with your buddy and only hang for ~ 80mins.

If you dont have your O2 it might be because someone stole your deco bottle, in which case they probably stole your buddy's also.

 

[1atm]

If you dont have your O2 it might be because someone stole your deco bottle, in which case they probably stole your buddy's also.

That reminds me of the thread on here about stolen bottles ... one would hope that some form of leak, although unlikely especially if you turn off as you should, is more probable than a stolen bottle. Nevertheless, if there is the slight risk of freediving clowns that might steal bottles, I carry them further into the cave.

The assumption remains that no cave diver would steal your bottles (that have your name on)... that’d be attempted murder in my books.

 

[rjack321]

If you dont have your O2 it might be because someone stole your deco bottle, in which case they probably stole your buddy's also.

Yeah 20ft isn't nearly deep enough at a cave like Ginnie.

 

[Manatee Diver]

Leave it inside the Gallery instead of in the Eye?

 

[rddvet]

Leave it inside the Gallery instead of in the Eye?

I used to leave it behind the first sign in the eye. Never had an issue. Then a couple people got their bottles stolen, so now I usually leave in the gallery. I'd probably still hide it behind the sign on a cold day when it's not busy with swimmers, but nowadays I almost always go in the ear and out the eye, so the gallery's the only option.

 

[rjack321]

Leave it inside the Gallery instead of in the Eye?

Down at the sign is a reliable place to stash your O2.

 

[Manatee Diver]

Down at the sign is a reliable place to stash your O2.

They seem to grow like mushrooms in the Gallery.