Bailout rebreather?

[Thrutch]

Hello, rebreather divers! I'm not one of you yet but hope to be as soon as I can scrape together $10k for all the bits and training. I was talking to a young man at my LDS about how I'd been ogling the KISS Sidewinder, and he told me about an instructor who uses it as his "bailout rebreather." For clarity, I made sure I understood correctly: in certain situations, this instructor supposedly brings an entire backup rebreather for redundancy's sake.

I have tried to find any reference to this practice and can't. As I said, I am not a rebreather diver, and I can't tell if this passes the smell test. Do people really bring entire secondary units on dives? What sort of dive would necessitate such a thing?

I have more questions where those came from if it really is a thing people do. I'm dubious.

Thanks!

 

[Whitrzac]

Yes its a thing for bigger dives. Its one of those things by the time you need one, you'll know everything about them.

 

[broncobowsher]

Yes, it is a real thing. It is also not very common.

So with every rebreather you need a bail out plan. Expect the rebreather to have a problem and it is no longer a piece of life support. The normal thing to do is bring a bail out cylinder with you. As you get deeper and have more deco obligation you need more bail outs. That is enough open circuit gear to get out of the water given the rebreather dies at the worst possible point in the dive plan. At some point you have a massive amount of bailout cylinders hanging off you. So you change all those bail out cylinders for a separate, nothing interconnected rebreather.

Used in deep (100m) dives and deep cave penetrations.

Looks like someone else has posted above me, lets see how much info overlaps.

 

[Thrutch]

That's wild.

 

[KevinNM]

When you reach a certain point in cave penetration it is basically impossible to carry enough gas to get out alive if your rebreather breaks far in.

At that point you also are pulling a spare DPV with your team. And have support divers awaiting your return.

I have no real idea how many people ever do those kind of pinnacle dives, but it’s a tiny percentage of rebreather cave divers.

 

[PfcAJ]

The distances that require a 2nd rebreather are FAR. All the world record WKPP diving except for like the Q Tunnel push (nearly 28,000' at 280avg) and maybe one or two others were planned with full OC bailout being an option. In the case of Q, Casey McKinlay and Jarrod Jablonski took a "stage rebreather" and used it for a portion of the dive, and another for deco for the longest ones (IIRC, it was a long time ago). Neither of those were "bailout" rebreathers, and those dives were at or approaching 24hrs in duration. I think Jon Bernot and Charlie Roberson had bailout RB80 rebreathers on their world record dive at Cathedral (30k+ at 170'ish) a few years ago.

What a bailout rebreather DOES do really well is eliminate logistical challenges. Short window to dive that precludes thorough setup? Issued with other teams sabotaging stuff (EKPP encountered this on a few of their early 2000s explorations)? Yes, it makes sense. But really, for the extreme vast majority of dives, its just complicates things. You've got to monitor it, make sure it doesn't flood, maintain it, and you still have all the associated risks of a rebreather. OC is simple and reliable.

Its my firm opinion that most guys with bailout rebreathers have it because its "cool" or they're too lazy to set up the caves they're diving properly. Probably a good dose of each. A few unique situations aside (real far, real deep), there's not a lot of genuine utility for them.

 

[rjack321]

Its my firm opinion that most guys with bailout rebreathers have it because its "cool" or they're too lazy to set up the caves they're diving properly. Probably a good dose of each. A few unique situations aside (real far, real deep), there's not a lot of genuine utility for them.

At one point I was debating making an O2 deco RB. No cells, just something with warm gas to breathe on an extended BO deco. I do have something at the test stage and tried it once. Constructed from a drager ray scrubber in an ali tube with MSR dromedary bag counterlungs, has a Kiss orifice and O2 MAV. Was originally planning on using it with an al6 of O2.

But its heavy-ish and in cold water, the duration of the Drager Ray scrubber isn't really significantly longer than an al40 (Ray=90mins, a 40, assuming you're willing to stretch to a max ~75 mins by moving up to 10ft as soon as you can). You also have to haul it all the way back there and keep it from flooding. Whereas if I flood the mk2 first and r190 2nd on an OC deco bottle it doesn't matter at all. And all that assumes your buddy's al40 of O2 and 50% is totally unavailable which is a second+ major failure. Bringing an 80 of O2 or a 3rd al40 is getting to be increasingly problematic 5 sumps back in this particular cave. But 80cf of O2 in two al40s for 2 CCR divers with ~90 mins of deco is not suicidal levels of danger (there's 2x al40s of 50% too)

Bottomline, the O2 deco RB remains a garage relic for now.

 

[GF99/99]

Yes this is become more and more popular as people are pushing the limits of overhead exploration and deep deep dives.

You could really spend hours and hours discussing this topic, its not a new concept but its just not commonly seen so there are lots of different trains of thought on it. TDI has a nice generic write up on it, does not go into much detail but give a good explanation of the general idea. Using a Bailout Rebreather - SDI | TDI | ERDI | PFI

Also Divesoft has been really pushing to make there sidemount unit as a bail out rebreather a mainstream thing, they even have a BO rebreather mode on there proprietary computer.

I am in the process of transitioning to a Triton as a BO unit. Similar to this I have some friends using this unit and are very pleased with it also is a very nice deco unit.
<iframe width="560" height="315" src="" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

Other route is to go with dual rebreather. Some have been playing around with this concept for a while now by banding two canister together like a twinset. I think Craig Challen and Richard Harris really set the standard for this with the dual Meg.

<iframe src="Pearse Resurgence 2020 from Richard Harris on Vimeo" width="640" height="360" frameborder="0" allow="autoplay; fullscreen; picture-in-picture" allowfullscreen></iframe>
<p><a href="">Pearse Resurgence 2020</a> from <a href="https://vimeo.com/divedoc">Richard Harris</a> on <a href="Vimeo | The world's only all-in-one video solution">Vimeo</a>.</p>

<iframe src="Twin Meg breakdown from Richard Harris on Vimeo" width="640" height="360" frameborder="0" allow="autoplay; fullscreen; picture-in-picture" allowfullscreen></iframe>
<p><a href="">Twin Meg breakdown</a> from <a href="https://vimeo.com/divedoc">Richard Harris</a> on <a href="Vimeo | The world's only all-in-one video solution">Vimeo</a>.</p>

 

[Heat Miser]

am in the process of transitioning to a Triton as a BO unit

I was told by someone more knowledgeable than me that the problem was fitting a solenoid to the triton and using it as a BOB. Listening to Richard's breakdown of the twin Meg's above it appears that there is a lot of dual management of pressures, and a solenoid seems to me it would be important.

 

[grantctobin]

I was told by someone more knowledgeable than me that the problem was fitting a solenoid to the triton and using it as a BOB. Listening to Richard's breakdown of the twin Meg's above it appears that there is a lot of dual management of pressures, and a solenoid seems to me it would be important.

Why would a solenoid be necessary? You can do this 2*mCCR (w or wo constant flow or needle), 2*eCCR, or a mix.