Gas Management for Peacock III/Syphon?

[mgif99]

Just curious what kind of gas management plan people use when diving Peacock III, or any syphon for that matter. I've only dove Peacock III once before, and having never been there before, we dove 1/6's. At the end of the dive, that seemed way too conservative. Do people dive it the same as Peacock I? (since both seem essentially no flow). I completely understand the argument that 1/3's is not conservative enough in a cave like Peacock, but what are people really doing in Peacock III? Thanks for your thoughts!

[PfcAJ]

2x gas to exit in reserve

[Sludge]

I haven't been in P3 since 2004, but in all the times I've been there, there's never been enough flow to even realize it's a siphon.

[Mark Vlahos]

Usually I can't tell it is a syphon, so I just add 200 to 300 PSI on top of my usual reserve. There have been a couple of times when the pull was stronger. On those occasions I have been known to dive quarters instead of thirds. For a strong syphon I will dive sixths or look for a different cave.

Mark Vlahos


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[RN]

Usually 1/4s, never more than 1000 psi penetration. When I see all the duck week being sucked toward the entrance then it's more conservative. Although P3 doesn't usually have much flow I have seen it siphoning at a pretty decent rate a time or 2.

[SlowDiver]

This topic brings back a memory of that system that was a learning experience. About 10 years ago I was diving P3 using alum 80 as travel gas, and 104's as back gas with trimix. Also put a 45 with O2 at the entrance. The travel gas was dropped off after breathing it down 1/3 and continued on to Henley and the rest of the cave on back gas. On the way out switched from the back gas (trimix was even expensive back then) to the travel gas alum 80. On the way out swimming against the strong flow I sucked the alum 80 dry. Still had plenty of gas in the 104's which I switched back to but I was still surprised at how fast I emptied that bottle, and this was not my first dive there.

[LiteHedded]

If you have a lot of gear on you you will notice that flow on exit

Arbitrary rules like quarters or sixths don't make much sense to me. I think you should put more thought into it than that when diving siphons.

[JamesK]

I usually dive it in fifths. I look at it this way;

3600 fill
3500 rounded down
700 to get in with
2900 in reserve
1450 for me
1450 for my buddy

That gives each of us twice the gas getting out as we had coming in. If it is syphoning harder, then I adjust fire from there. If I take a stage, then I breath it to thirds unless my buddy is at thirds first, then I drop it when they do.

[aquadog196]

if you have a lot of gear on you you will notice that flow on exit

arbitrary rules like quarters or sixths don't make much sense to me. I think you should put more thought into it than that when diving siphons.

ditto, ditto, ditto

[DA Aquamaster]

Same here.

We rarely dive to thirds unless we're doing a swimming dive someplace with strong flow out like Ginnie or JB. In no flow/low flow caves we normally pad our gas reserve by reducing the penetration gas by 100-200 psi. In a siphon, we add reserve on top of that based on how much of a siphon we're dealing with, and if it's stronger than anticipated I'll change the plan to increase the conservatism even more. I look at cave diving like I do aviation, where it (almost) never bothers me to stay fat on gas.