Solo Sidemount Gas Management

[cmint]

Just curious what you guys do for sidemount gas management when diving solo. I'm going to attempt to make this a poll.


Thirds? Fourths? Sixths? any half plus two'ers?


I know it may depend on the dive, for this one let's use a typical full cave dive at Ginnie or Peacock. No siphons, no mount stuff or anything odd.

[Peter Buzzacott]

Fifths is what they teach in the FFS in France and I have been comfortable with that at various times. The thinking is, when you lose a tank at the turn then you'll still have twice what you need to exit, in case of delay or stress etc.

Of course, I would re-evaluate my comfort with this plan with increasing depth, high flow, restrictions or other potential delays to the exit, use of DPV, etc.

[FW]

Too many variables. I start with thirds, but add gas for each restriction, or anything else that might slow me down. I never dive all the way to thirds, even in big easy passage. Remember if you loose a tank, a third of that will just barely get you to the entrance, not even enough spare gas for a safety stop.

[tbone1004]

I dive with thirds, but have no issue recalculating and typically don't pad it much more. My Poseidons being semi upstream allow normal breathing in event of a HP failure, so I'm OK with pushing it a bit, especially if it's poking around on the way home, or would in places like Peacock where you're never particularly far from an exit. No solo allowed there though so we have to remove the Swiss Cheese from the equation. Desperately wish there was solo there, but alas, that's a dead horse not worth beating.

so yeah, I dive to thirds, but unlike doubles, I have no problem diving up to thirds because most of the gas should be available in a slightly less annoying manner than backmount. I'll try to feather it through big easy passages, and stay on that bottle as long as I can in event of a failure.

[nakatomi]

Due to a recent switch to a very popular side mount rebreather, I do not have any of these constraints.
My single 80 diluent will last forever as will the 2l O2 tank. So there are no thirds, quarters, sixths or whatever.
The final frontier is the scrubber which, in a 2-3Kg setup, will last anywhere from 3-12 hours depending on who you ask.
For added perfect safety and to account for 2+ catastrophic failures, I'm going to add the proven 6 cuft bailout system, as seen on Facebook..
Life is good.

[Nitrogenius]

For added perfect safety and to account for 2+ catastrophic failures, I'm going to add the proven 6 cuft bailout system, as seen on Facebook..
Life is good.

lol


I do 4ths on base SM tanks solo and thirds on stages. I drop the stages at thirds and last part (on base SM tanks fourths again). That keeps me at a minimum of additional 50% reserve for any catastrophic failure..
Additional safeties potentially added as described by forrest (restrictions etc.).
I have to admit though .. not doing anything "too heavy" solo anyways..

[Jay]

I do thirds solo in hi flo. As FW said, situations dictate more reserve or a stage.

[rysparks182]

Too many variables. I start with thirds, but add gas for each restriction, or anything else that might slow me down. I never dive all the way to thirds, even in big easy passage. Remember if you loose a tank, a third of that will just barely get you to the entrance, not even enough spare gas for a safety stop.

Not to mention the added air consumption due to stress.

[FW]

Not to mention the added air consumption due to stress.

That is why I turn earlier, to avoid stress caused by not having enough gas to exit, in case of a failure.

[DA Aquamaster]

Two thoughts:

1) I'm in agreement with Forrest that it can't be reduced to a simple rule - thirds fourths, sixths - what ever. Like Forrest, solo dive or not, we base the turn pressure on the conditions of the dive - number of restrictions, difficulty of those restrictions, whether we've made that same exit before or not, un-restricted passage size, silt and potential for silt, presence of old or loose line, flow, depth, etc.

Tank size also makes a difference. For example, if you're swimming to the tight bit at the end on one or more stages to preserve all the gas in the primary tanks for the tight bits, and those primary tanks are small (LP 45s etc) due to the size of the passage or restrictions, then I'm going to be even more conservative in the gas plan, both overall, and especially in regard to the gas in the primary tanks.

2) I'm appalled by the number of cave divers in the poll who've selected "thirds" as an acceptable gas plan for a solo dive (6 at this point, with 2 voting for fourths, and no one opting for sixths). I guess having the half plus 200 option makes thirds look "conservative".

Are those six divers not aware that the rule of thirds was developed with a team of three in mind? Have they somehow lived in a bubble and remained unaware that most critically thinking cave divers regard thirds as inadequate for a team of two?

That's seriously screwed up. We have six cave divers who think a solo side mount dive to sixths is a viable gas plan.

Hopefully these six are not making it an order of magnitude worse by actually considering a solo side mount dive in true side mount conditions. Hopefully they are instead talking about a large passage main line dive in side mount configuration somewhere like Ginnie where the flow might get them out alive if they experience a failure at max p.