In this thread, I would like to share our process of choosing to transition from eCCR's to mCCR's for the benefit of anyone thinking of buying their first rebreather or making a switch and get feedback from the wise and experienced ones on the exact configuration of our new Copis’s, which are due to hatch on june 20th. This is a summary and somewhat repetitious of other posts I have written over the last several months. My appologies in advance, in attempt to be comprehensive and thorough, it grew quite lengthy.
My wife has recently decided to stick with CCR diving, but she is requiring we get something new and different, together and I have agreed. The repeated solenoid failure she had with her previous rebreather has made her quite leery of set point controllers and solenoids as a general rule, which is understandable, we bought what is arguably the most user friendly eCCR out there and she still missed dives. I realize the risk that we might be over reacting to her unique and uncommon experience by giving up on eCCR’s all together, but sometimes you just have to give something else a solid try to get the needed comparison. I see a variety of benefits with going mCCR so I’m not really putting up much resistance, in fact I’m excited for something new and different...we can always go back, and if we do, it will be with a lot more solid understanding of whether the benefits of automation are worth the price of additional failure points, additional maintenance and additional risk.
I know many folks will say “Ive been using X eCCR for years without any problems, I think you are over reacting”. The bottom line is that all electronics fail at some point. The fact is that my experience on the Evolution has been virtually flowless too. This post is not about bashing AP, I think they have a great product that seems to be very effective at catching problems before they become fatal... hearing complaints is actually a better sign than not hearing from someone ever again, and vision has near zero fatalities. So i'm really opening this up to eCCR's in general, statistical analysis is impossible with a sample group of one or a small group of friends, so it’s difficult to draw solid conclusions from our own personal experience. The risk of death on eCCR’s is small enough that the average diver does not come across the lethal cocktail of circumstances that lead to death in ones years of diving, so the fact that one has survived is not actually that helpful in affirming which practices or style of rebreather are really the cause. To get valuable numbers to steer development trends you have to look at large sample groups. I’m talking about the big picture and applying pure outcome statistics because, frankly, quality imperical accident analysis, while worth attempting, has proven perpetually hypothetical due to the basic limitation of not being able to gather enough objective data in each incidence. I don't think this is going to change any time soon. At this point we have really one major thing to go on, that mCCR’s are associated with an infinitesimal number of accidents, while eCCR’s have a high actual mortality rate. The bottome line: an mCCR diver could die every month for the next couple of years and the difference would still be striking.
I hear many folks say they drive their eCCR’s manually and use the Controller as “a safety net”, kind of like having the best of both eCCR and mCCR worlds. So you might ask why we aren’t simply changing our habits and keeping our Evo's? The trouble with this logic is that the very thing that you are relying on as a safety net is the most likely part of an eCCR to malfunction. I see value in the “fly manual” philosophy embraced by so many eCCR divers and see that it likely reduces risk and increases good habits on an eCCR, but I am skeptical that it truly matches the good habits and still results in the high maintenance associated with an eCCR. You are paying a premium and not even really getting to enjoy it’s conveniences. Furthermore, we have tried flying our eCCR’s manually, but it’s all to easy to get lazy and slip back into letting the controller take over, your life is not so apparently at stake. With mCCR’s, the right attitude is constantly being drilled into you, you don’t have a choice, pay attention or risk death. With eCCR’s you are constantly trying to convince yourself that you should have this attitude, but I think the lack of immediate consequence is just not convincing enough to the conscience mind to make it a continuous habit. The set point controller as “safety net” is tempting logic, and is probably a step forward in eCCR diving, but I am skeptical that it’s not really equivalent to CFO/+manual injection top off. I’ll go a step further and say I’m even concerned for eCCR divers that call the set point controller “a safety net”. It seems to me like a dangerous oxymoron, leading pardoxically to a false sense of security. Among other limiting factors, an eCCR has a very stilted voting logic capacity, as compared to the brain once entrained to truly engaged constant monitoring, able to verify which cell or cells is to be trusted, on the fly in the event a cell goes south. mCCR diving more deeply entrains one to truly factor cell verification in every time the manual addition valve is hit. As it turns out, the reverse paradox seems to be more true, that the lack of trust engendered by operating the mCCR system seems to breed true security. It has been uttered so many times “electronics can’t save you”. So it seems, all things equal, our best efforts at skill building and diligence will likely result in less overall risk if we go mCCR.
Flying an eCCR manually is also not as convenient as flying an mCCR manually, having to inject so regularly, and lacks the more true safety net of a CFO that is less likely to fail you at the worst moment than an electronic set point controller.
Further, CFO’s may be as responsible for the Zero fatalities with mCCR’s as the habit of flying manually. They seem to offer a safety net with fewer holes -do nothing and life sustaining oxygen will continue to flow- and requires infrequent injection if adjusted properly. Sure it could plug, but monitoring it constantly is already a must, so you are more likely to catch that and simply manually add more often as you abort the dive. It’s a natural conclusion to me that the Constant Flow Orifice, combined with manual injection actually strikes the best balance of simplicity and convenience.
For me, insuring good habits and greater reliability comes before convenience of auto injection in the hierarchy of needs. Add a redundant po2 monitor to the robust build of a Copis and why would this not be the ultimate CCR for just about any kind of diving? Totally field serviceable, modular, incredibly reliable, fewer moving parts, less complex spare parts kit, true electronic redundancy… and they even offer a technician course for it. And you have your choice of computer type for deco and CNS to add, in line or stand alone, and you have a pretty bullet proof set up that you can take to the most remote places on earth with greater confidence that you won’t miss dives.
But, still, mCCR’s are depth limited you say… or are they?
It seems to me that the depth limitations of a constant flow orifice can be easily overcome by an additional, small bottle of off board o2 with a pressure compensating first stage for the short portion of a deep dive, below a depth where the IP of the CFO is exceeded and you already are carrying bail out on a pressure compensating first stage that can be used for dilluent.
It seems that plumbing in a separate po2 deco computer has it’s advantages over having your handset be an all in one cambo. you have separate power sources, totally independent electronics, batterie compartments, displays, and if your preferences change you can buy a new constant po2 computer without buying a whole new rebreather
(barrowing what I think is a valuable isolationist principle from the KISS). Again, I’ve gathered the only thing a Copis is missing is a truly independent second po2 display, which is a good idea at any depth, so we are planning on giving one of the three cells to a shearwater for in line deco and independent, mental voting logic.
I just don’t see the need for putting all 3 cells on one monitor and adding a 4th for in line deco. 3 cells are really only needed for the voting logic of an eCCR set point controller. And I don’t like the idea of two po2 monitors sharing 02 cells, otherwise I’d parallel the shearwater and stock handset on all three cells. Instead, I’m barrowing the "two cell primary for po2 monitoring" concept from the Palagian design and adding the shearwater on the 3rd cell. If one of the cells goes south, I will abort the dive and ascend using the remaining two. If the remaining two start showing different readings then it’s time to bail out to OC and replace the offending cells back on the boat. And if either po2 monitor goes, i can hook up all three cells to the remaining monitor and continue diving on a trip with relative safety.
After much deliberation, this is the direction my wife and I are going, not so much for deep diving yet, but I like knowing the Copis has that capacity and can even be upgraded to an eCCR if I find that that is necessary down the line.
I’m ultimately pursuing what the best mix of simplicity and electronic convenience is, striving for the characteristics of mCCR diving that are resulting in the habits responsible for their zero fatalities and looking forward to ease of maintenance and added reliability for the relatively shallow, recreational diving we do. I’m looking to adjust my style and type of CCR diving to minimize, even eliminate fatal risk (within reason), skill and diligence notwithstanding, and to do our best to assure we can go to remote locations and deal with just about whatever problems might arise so we don’t miss any more dives. Being primarily a recreational diver, I’m also encouraged to find that mCCR’s may not only be the most affordable option, making them more available to the masses but they appear to be the safest and most reliable. I believe the development of this sector of the market is key to seeing rebreathers come within reach for the recreational diver who mostly just wants move beyond the bottom time restrictions of OC. Perhaps mCCR's are the wave of the future for the recreational market, and maybe even for the deeper divers as well.
Give me your best affirmation, addition or argument against this thinking. I don’t want to leave any stone un turned as I further develop my knowledge base.