Survey question rebreathers

[odin]

In the overhead environment how many bailout bottles? PO2 set points for 100' dive.

[PfcAJ]

I think that would depend on the size on the tanks and the distance from the exit.

[H2Ocaver]

Not enuf data...

[sam]

Is it 100' for 3 hours? Scooter?
Too many variables to answer as asked.

[floridabob]

Hmmmm. Rick-- why would you even ask? You don't use a machine.

Guessing it's to make sure people you dive with bring adequate gas.

So, most in our group do not plan team bailout for the penetration phase but do for deco gas. Bit oversimplified but, we plan the exit portion self sufficiently but may stash less than all the necessary deco gas for all to deco open circuit...might plan 50% failure rate on that portion. I was taught and follow 2x the necessary exit gas.

Variables influence the exact numbers but:

2x the penetration gas for each diver (plan solo/self sufficiency)
Deco at 50% needed open circuit gas or more (3 divers means 2 guys have OC) bailout

I know of quite a few that plan team bailout for penetration segment but I'm not comfortable with that...I saw three guys go past the Hinkle and each had AL 40s. Too light to me.

As for set point, does depend on time. But for what I know you do id think most who dive with you would be between .9 and 1.1....maybe some would even choose 1.2, but that's a bit hot unless it's really short. The deeper stuff might be around .8 or.9 depending on BT.

Hope that helped some.

Bob

[Captain Bil]

...I saw three guys go past the Hinkle and each had AL 40s. Too light to me.

Really? Amazing.

Sent from behind a pint of Guinness.

[floridabob]

My understanding is that a rule of 1.5 times the amount of gas is taught in some classes. And in the team bailout scenario that gas can be spread out among the team. Using that number I can see how 40s work.

From Add Helium:

The agencies that teach team bailout state it as a minimum standard to which a diver must comply. Briefly stated it says that a team must have a *minimum* of 1.5 times the amount of gas required to get the team member with the highest SAC rate out of the cave. I have no issue with anyone who chooses to use that formula. For a highly disciplined team in a circumstance where it is not possible or feasible to take more gas this method works just fine and is actually safer than the age old rule of thirds. I will not go through the math here but suffice it to say that the rule of thirds give the exact amount of gas needed with no margin for error while team bailout provides a 50% margin for error, provided you don’t lose your buddy.

Bob

[nakatomi]

That 1.5 times bailout margin must be an open water thing

I was taught to always carry at least twice of what is needed to get out, as a rock bottom bare minimum.
IMO bailout for a rebreather should be at least twice the amount needed to swim out, especially considering the fact that having to bailout is a very likely event compared to a catastrophic gas failure in OC.

Two bailout tanks sound like a plan too, redundancy and the ability to share gas and bail out at the same time.

Clearly two Aluminum 40's would not provide enough gas to swim back from the Hinkel. Maybe they had placed scooters and stages somewhere and the two 40's was just the bailout gas past the restriction?

For the Hinkel, two completely full 80's would probably be the bare minimum bailout.

http://www.cavediver.net/old_reports/cdf_report_103.htm

My understanding is that a rule of 1.5 times the amount of gas is taught in some classes. And in the team bailout scenario that gas can be spread out among the team. Using that number I can see how 40s work.

From Add Helium:

The agencies that teach team bailout state it as a minimum standard to which a diver must comply. Briefly stated it says that a team must have a *minimum* of 1.5 times the amount of gas required to get the team member with the highest SAC rate out of the cave. I have no issue with anyone who chooses to use that formula. For a highly disciplined team in a circumstance where it is not possible or feasible to take more gas this method works just fine and is actually safer than the age old rule of thirds. I will not go through the math here but suffice it to say that the rule of thirds give the exact amount of gas needed with no margin for error while team bailout provides a 50% margin for error, provided you don’t lose your buddy.

Bob

[Captain Bil]

I don't dive with very many RB folks, but even if I did, I don't think I'd be comfortable with the Team Bailout thing ever, especially in an overhead. When we cave dive the RB's, we always carry enough gas to get out comfortably individually. We will leave deco gases in more of a team B/O configuration for caves like Jackson Blue, but for something like the Nest, even the deco B/O gas is planned individually. Outrunning my bailout is one of my major concerns when cave diving the RB.

Two bailout tanks sound like a plan too, redundancy and the ability to share gas and bail out at the same time.

Clearly two Aluminum 40's would not provide enough gas to swim back from the Hinkel. Maybe they had placed scooters and stages somewhere and the two 40's was just the bailout gas past the restriction?

For the Hinkel, two completely full 80's would probably be the bare minimum bailout.


This makes more sense, but I doubt they staged more stuff. More likely they planned team bailout and assumed only one RB would fail at maximum penetration. Scary.

[FW]

Another way to look at it. For any given amount of bailout gas, the MOST you can safely penetrate is 3 times what you could do on the same gas open circuit.
For example, if you can get 1500' on a set of doubles OC, then the MOST you can do on that same amount of gas is 4500'. Think of it this way. On open circuit it is 1/3 in, 1/3 out, and 1/3 for emergencies. On closed circuit, you can use all 3 thirds for emergencies.

I use 1.2 as a set point at 100', if the dive is under 2 hours. I have seen from 1.0, to 1.3 used. For longer dives, the set point should be lower.