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stuartv

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I’d echo the above. Saying you’re on your way out, it doesn’t need to be as polished is asinine.

Yeah, piling on to problems by ruining visibility and/or ramming gear into rocks ain't gonna help any or make an already limited gas supply last longer.

It wasn't my comment. I just shared what someone said to me. But, I feel like you are taking the statement "OC buoyancy doesn't need to be as top notch as what an OC cave diver would have" and interpreting then responding as if the actual statement made was "OC buoyancy can be crap."

My fifth and sixth dives after I finished OW were the two loops in Dos Ojos cenote. That is pretty shallow (i.e. harder to control buoyancy than a deeper dive). I somehow managed to follow the guide and the line all the way around both loops without ever touching the ceiling or the bottom - including not banging my tank on anything.

Does that mean someone with 4 OC dives has good enough OC buoyancy for CCR Cave? No. But, I submit to you that the buoyancy required to follow a line out of a cave, without banging into stuff and without silting it out, is easier than the buoyancy required to, for example, tie off a line correctly as you are going into a cave. It seems entirely feasible to me that someone has been diving enough to be ready for CCR Cave could very well already have good enough OC buoyancy that there is really NO reason to make them take an OC Cave class first. However, I have no cave training, so I could be completely wrong. I will have to rely on my eventual CCR Cave instructor to tell me if my OC buoyancy is good enough or not.
 

stuartv

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@stuartv , one thing I've learned from OC cave diving is a healthy respect for how much gas you need when there is an issue and how quickly a limited supply dwindles when you are far back and "agitated". I use the term agitated because that's how I've felt at times after hours of diving when I'm sweaty, hungry, and thirsty and it's a long long way to my deco bottles and even longer to the surface.

A friend took zero to Hero Cave CCR. It was a giant "trust me" dive that took him to places that had very real world potential to have a very bad day if something happened to his instructor. He didn't have the experience or muscle memory to deal with being lost (hadn't even done a black out drill). He's a great diver with a solid head on his shoulders, sadly he hasn't realized yet how bad things could quickly.

The mentality I see from zero to hero ccr cave divers is a belief that "I have all the time in the world to figure it out" if there is a problem. Vs cave divers who learned on OC that understand "I have the rest of my life to figure it out".

I have that respect as well, I think. I watched as my buddy got entangled once, at 300', on an OC dive. My Pucker Factor was at 11. The ability (and judgment) to properly plan BO, including appropriate factors for high-stress SAC rates, seems like an instructional issue.

Your friend's Z2H Cave CCR class sounds like a good example of bad instruction. Not necessarily a basis for saying that he should have done OC Cave first.
 

Jack Hammer

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@stuartv, the Dos Ojos cavern is a simple dive and doesnt really compare well to the types of restrictions common in many cave systems, including including those found not too far into the actual cave itself at Dos Ojos. Many caves have quite a bit of up and down and passages with varying ceiling heights and widths that go from very large to barely fitting through, not to mention varying amounts of flow.

It's really difficult to appreciate just how much gas you can burn through on OC in a cave from bad technique without actually experiencing it. And flow pushing you out isn't always your friend. It can really highlight bad technique. Personally, at minimum I think all C1/Intro should be on OC. Then maybe CCR for full/C2 on a case by case basis.
 

Brad_Horn

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I have only seen one in person very briefly but the water tolerance on the Mares Horizon *should* be much greater than a normal rEvo. The exhale counterlung acts as one giant water strap and there are dump valves located on the bottom of each lung (according to the manual)

They must not teach de-watering in the class as the Horizon manual recommends not to pull dump valves or risk flooding the unit.
View attachment 670217
If they ever make a rEvo IV I hope they use this lung configuration. In theory it should add some flood tolerance to the rEvo.
If you're seriously interested in underwater flood recovery, a solution for the above issue was engineered and openly disclosed, a while ago. Mares/rEvo are fully aware of it!
A factor for consideration is it cost Open Safety ~$150k to solve this particular problem, through some pretty dedicated engineering resources and a lot of R&D, for what many may consider a minor issue. And as Open Safety are still the only manufacturer to offer a fully flood recoverable unit....

You can likely make use of these waterdumps as you'll note some similarity in CL layout exists between these units; but, it would be a lot safer if you are diving with a Micropore EAC, as you both lower the caustic cocktail risk and your WOB doesn't go through the roof from wet sorb due to poor design.

"Apocalypse CCR - Waterdump upgrade
There was a chance that when clearing a flooded loop the original water-dumps on either Apocalypse Type IV Counterlung would not perfectly reseat, 1st time, every time. Potentially, if they were operated a second time they sealed, but it wasn't always perfect.
A better product was requested for when OC bailout is not an option and the diver must remain on the loop after recovering underwater from a full flood.
Open Safety previously used a make of BCD water-dump which was widely used for rebreathers. On receiving the feedback, we bought and tested more than a dozen different BCD dumps, but did not find any that were ideal so we designed our own water-dump. We created seven new injection moulded parts and two new moulded seals: this was not a trivial exercise."
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macado

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Also, FULLY flooding a rEvo from a torn mouthpiece seems like a bit of a stretch? Unless it tore and the loop came out of your mouth and floated freely for some time while open?

You kind of make that sound like diving one of your Top 4 (instead of a rEvo) would somehow allow you to carry less BO?

Or, you're saying that you feel like there is a greater chance of having to make an OC exit on a rEvo than one of the others. Again, I have to wonder if that is a realistic concern or an "on paper" concern? Not that you couldn't have to make an OC exit. You could - but you could on any of them. The question is whether there is actual data - not just theory and anecdotes - that support that idea that an OC exit is more likely on a rEvo than one of those others.

Maybe I explained it poorly but the mouthpiece was just one example that I could think of. Take a mouthpiece out the equation and replace it with something like a tiny tear in a loop hose or maybe a bad o-ring or a stuck OPV/dump valve that slowly lets in water. I'm generalizing. A seemingly minor and often overlooked thing can slowly cause a rebreather to flood. It may not be an issue on a 2-3 hour dive but imagine slowly flooding the loop on a 6-7 hour dive with no way to de-water it.

Actually to your point a buddy of mine (not on scubaboard) back-rolled off a boat and the mouthpiece came off his loop. It was obviously his fault but he completely flooded his rEvo. While this didn't happen on a dive we were unfortunately 25 miles offshore so that was the end of his dive day.

On the SF2 I could literally take the loop out of my mouth underwater, shake it and completely flood and then clear it. I personally never did that but I know people who did just to prove a point and test the theory.

I didn't mean to say that I could carry less bailout but my point was more on a typical ocean dive with a runtime less than ~2.5 hours I can easily be self sufficient and carry enough bailout. If all I ever did was 2-3 hour ocean dives then I think flood tolerance would be a lower priority on my list of things.

I'm not a big believer in team bailout philosophies but arguably this gets pretty hard on a 6-8 hour cave dive. You may have staged multiple safety bottles in the cave that you've agreed to share with your teammates. On some Florida cave dives you may be carrying ~250-300cu/ft of bailout gas / bottom mix in addition to other stages and deco gases you've already dropped. I would be pretty pissed off if I had to use all this gas because my rebreather flooded. Yes you plan for it and **** happens but I'm all for mitigating risks. One of the ways I can do that is choose a unit with flood tolerance.

I don't feel you're being argumentative. I'm all for healthy discussion and discourse as long as it doesn't turn to insults. One of the reasons I don't typically engage in these discussions online is that people have already made up their mind. Some people just love to argue for the sake of arguing. People are set in their ways and absolutely convinced of the superiority of their rebreather. Most people are delusional and convinced that if the **** hits the fan that they're going to act 100% on their training. They will bash every single rebreather that is not theirs until they're blue in the face, no rebreather is immune to criticism.

Completely unrelated to this conversation but the last high profile rebreather death that happened got very ugly with arguments online. It quickly escalated into nasty arguments and chest thumping about O2 management, HUDs, training, etc. I try to avoid those arguments.
 

rjack321

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When I did my original rEvo training, I asked my instructor (who is also a cave diver) this question. I.e. do I need to do OC Cave first, before going CCR Cave? Her answer was "once you're diving a rebreather, why would you EVER go INTO a cave on OC?"

Going in is always optional. Exiting is not.
Learning OC cave on a bailed out exit is bad news.

At the very least take cavern and intro/apprentice, NAUI cave 1, or something similar on OC before you add the complexities of a CCR and cave BO issues.
 

kensuf

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A few of the posters in this thread have either taken cave training or had their spouses take cave training with me, and I've taken macado on a couple of deeper guided cave dives. I'm in the do your first half of cave training on oc, second half on ccr camp too. We don't train for the best case scenario, we train for the fit hitting the shan; during a hypercapnia event is the last place you want to discover you don't have the skills or sufficient bailout to get home.

I've only been cave diving actively for a few years, so feel free to disregard me though.

The nsscds has a reasonable path to doing the first half of cave training on oc and the second on ccr. Joe Citelli, a good friend of mine that I've known for 25 (how did I get to be so old?) years recently crossed over to the cds and can conduct such a program. Although Mel is a cds instructor, she's only a ccr cave instructor and cannot conduct this program.

I'm heading to the docks to go jump on a wreck. Have fun y'all.
 

Jack Hammer

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On the SF2 I could literally take the loop out of my mouth underwater, shake it and completely flood and then clear it. I personally never did that but I know people who did just to prove a point and test the theory.
In my JJ class we did that, took loop out of mouth underwater and shook it to completely flood, then cleared it. It was actually quite simple to clear and a huge confidence builder in the unit for me.
 

kensuf

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I had a great time diving in Palm Beach today. 185' and a 2-3kt current all the way to the sand, but warm blue water. My Fathom performed flawlessly, as expected.
 

rjack321

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In my JJ class we did that, took loop out of mouth underwater and shook it to completely flood, then cleared it. It was actually quite simple to clear and a huge confidence builder in the unit for me.
Did the same on my Meg in the pool on day 1
Couldnt do anything remotely like this on a kiss
 
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