How great is the risk (in your perception)?

[_Slacker_]

Yes, understood. I was just trying to simplify the example and not necessarily represent the level of dive where spreading out resources would be required.

 

[CAPTAIN SINBAD]

True! This thread has been personally very enlightening on so many different levels. It provided answers to questions I did not even have. At this point, the thoughts floating in my mind are:

a). Rebreathers are an expensive way to eliminate one set of problems and totally replace them with another.

b). They make deep dives easy and shallow dives complicated.

c). The depths at which they truly "justify" the hassle, better be the depths you are diving quite frequently otherwise you end up taking the same risk in depths where it is really not necessary.

d). The depths at which they justify their hassle may also require so much bail-out that the advantage of not dragging loads of tanks may not even be there. These are the depths where "team bail out" becomes politically correct and opposing it becomes politically incorrect. If that is the case then why not hang decompression bottles with a rope all the way up?

e). Rebreathers are the future just like solar cars are the future but do I want to buy one today?

 

[tbone1004]

@CAPTAIN SINBAD there is also the aspect of changing your diving experience by going to a silent unit as well as minimizing the tick-tock of time in a cave.
If you have enough bailout for 4000ft of penetration, you can spend as much time as you want between home and 4000ft. You can come back to 3000ft, and take a 1000ft jump, then go back to 2500ft and take a 1500ft jump, all on the same dive with the limiting factors being your cold tolerance, hunger tolerance, and bored tolerance at deco.

 

[cerich]

See, this sounds much more logical to me. My rule for buddying with someone is I don't ever want anyone to rely on me for safety. If you NEED my help to prevent your death, you've done lots of things very wrong. If having me around benefits you in a way that increases your convenience but doesn't change the overall outcome...I'm happy to help and get help.

In terms of team bailout, I'm here to read as I can contribute essentially nothing.....but what you're describing sounds very much not like "Team Bailout" as I've heard it discussed before. If every diver has enough gas to get out while solo and having a buddy around helps make things even safer and/or more convenient then I see nothing wrong with it.

not to me, it doesn't account for each individuals different gas consumption.

 

[KenGordon]

True! This thread has been personally very enlightening on so many different levels. It provided answers to questions I did not even have. At this point, the thoughts floating in my mind are:

a). Rebreathers are an expensive way to eliminate one set of problems and totally replace them with another.

b). They make deep dives easy and shallow dives complicated.

c). The depths at which they truly "justify" the hassle, better be the depths you are diving quite frequently otherwise you end up taking the same risk in depths where it is really not necessary.

d). The depths at which they justify their hassle may also require so much bail-out that the advantage of not dragging loads of tanks may not even be there. These are the depths where "team bail out" becomes politically correct and opposing it becomes politically incorrect. If that is the case then why not hang decompression bottles with a rope all the way up?

e). Rebreathers are the future just like solar cars are the future but do I want to buy one today?

Your point D misrepresents to case. For OW dives in the 50m to 70m range you can certainly carry enough bailout. These are dives whose bottom time is limited on OC by backgas. On CCR they are instead essentially limited by deco gas, bailout being mostly deco.

E just makes you sound like a troll.

It is a shame bout the diversion into a cave diving **** fest.

 

[Dan_P]

I personally think there's a noteworthy issue in fundamentally replacing the base and basis of my diving completely as the needs expand.
That is, now I need to do deeper/longer diving, so woop - I can chuck away all my gear and procedures.
The same goes for the transition from rec to tec - I'd rather not have to replace a jacket-style bcd with a backplate, split fins with actual fins, and start over on technique, gas planning, etc.

I think there's good sense in reasoning that the change in diving/dive base impacts comfort/capacity/safety, and therefore, risk.

Then follows the specifics of the platform.

 

[kensuf]

There's another logistical advantage with CCR's that is being overlooked in this thread. With a CCR the time / effort / energy / cost to re-fill bottles after a dive is dramatically reduced. This is really pronounced when a person is diving in locations where gas availability is reduced or outrageously expensive, but it can even be a benefit in locales where gas is readily available.

Right now I could pack up my scrubber and prep my rebreather, drive to Eagle's Nest, and do a 5 hour dive. To do this dive safely, I would need appreciable bailout. The amount of bailout gas I need would probably look something like this:

Assuming everything goes well on the dive, and I do not need to touch my bailout, I would only need to refill two 3L bottles (oxygen and DIL) in order to go and repeat the same dive tomorrow. And the next day. And so on.

This can be a huge advantage when doing a multi-day series of dives, or in a remote location.

 

[LiteHedded]

usually but in your example for a simple dive requiring only 2 deco tanks we would just carry our own. When you start getting into 3 or more tanks then yes is is more for deco profile considerations than gas volume.

so three tanks is too much? that's when you split it up?

 

[tbone1004]

not to me, it doesn't account for each individuals different gas consumption.

@victorzamora and I choose to have near the same SAC rates, same drop points for stages, and dive the same tanks. It helps a lot

but yes, if you have wildly different gas consumption and the guy with the low sac rate doesn't drop stages at the same spot etc, it doesn't really do you much good.

our basic game plan is that on the way out in a situation like this, use the stages to balance the amount of gas that each of us have from a cubic footage standpoint instead of having one diver full, and one empty

 

[DA Aquamaster]

True! This thread has been personally very enlightening on so many different levels. It provided answers to questions I did not even have. At this point, the thoughts floating in my mind are:

a). Rebreathers are an expensive way to eliminate one set of problems and totally replace them with another.

b). They make deep dives easy and shallow dives complicated.

c). The depths at which they truly "justify" the hassle, better be the depths you are diving quite frequently otherwise you end up taking the same risk in depths where it is really not necessary.

d). The depths at which they justify their hassle may also require so much bail-out that the advantage of not dragging loads of tanks may not even be there. These are the depths where "team bail out" becomes politically correct and opposing it becomes politically incorrect. If that is the case then why not hang decompression bottles with a rope all the way up?

e). Rebreathers are the future just like solar cars are the future but do I want to buy one today?

Tom, Ken Gordon and Ken Sallot all addressed aspects of what's wrong with some of your assumptions.

When we bought rebreathers, the folks I know who liked to do deep 300-500 foot dives all made recommendations based on the deepest perceived dive, and this focus on "deep", and in particular "too deep for practical OC" is where the idea develops that you need to go deep to make the different risks of a rebreather worth switching from OC.

It's a mistake to think you should limit CCR use in this way. CCR gives you a great deal more time, which allows you to dive slower, and cleaner in tight passage without decompression being the major issue. And, as Tom says, if you've got enough bailout to penetrate 4000 feet (with strategic placement of that bailout gas), everything less than 4000 feet is also now available on that dive, or subsequent dives. And, as Ken S. says, it's gas you don't actually use, so you don't have to get fills in those tanks. Plus, if you are doing multiple dives in the system, you don't have to carry it in and out of the system on consecutive dives.

Also consider a dive off the map in Peacock - a shallow system for the most part - to the end of the Martz Offshoot. Doing that safely and reasonably cleanly on OC is problematic given the number of stages required and the small passage and restrictions involved. In contrast, it's not all that hard to do the dive safely on CCR, with what AJ considers separately as "safety bottles", placed on a set up dive, and/or on the actual dive, and only taking the last stages as far as is needed for a diver to get back to the last stage on the bailout gas actually carried by the each individual on the 2 person team. In effect you're carrying only 1/2 the total number of stages, compared to OC, as you only need to cover the gas to get out. That's half the gas, even if you plan for two CCR failures, or conservatively for a single failure with 2x elevated gas use on exit.

That's also the extreme case, as with the exception of the offshoots from the distance tunnel, and the water source tunnel, you can't really get much farther than 1000' from an exit in Peacock, which means you can do a very long CCR dive with minimal or no deco, and not have to carry the stages you'd need in order to do the same dive in OC.

CCR's benefit isn't just when you have excessive depth, but also when you want much more time, and/or much greater penetration in a cave environment.

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If we exclude AJ's "safety bottles" from the team versus individual bailout discussion, it changes the entire discussion and makes it largely irrelevant to cave diving. If a team of two only carries and places enough gas for one catastrophic, totally off the loop CCR failure, not two, it doesn't matter whether you call it "individual" versus "team" bailout. AJ is making the distinction that as long as one individual can locate and use the gas needed to exit, without any involvement from the other, then it is individual bailout where 1x the gas needed to exit is sufficient, while suggesting that 1.5x the gas needed for a diver to exit in a team approach is insufficient. The thing is whether it's1x, 1.5x, or 2x, the "team" is not going to carry gas any farther then necessary when placing it in the cave, where it's now a all "safety bottle" gas that is available for anyone- and seems to meet AJ's definition of "individual" bailout.

Which really reduces the whole argument to what do you do in open water with a soft overhead, as opposed to what do you do in a cave where you have both a soft and hard overhead.