A ScubaBoard Staff Message...
Cave Diver:
DAY 4 - We're about half way through mCCR 1 - me, Nick Ambrose, and John Walker, and it's so far been a pretty wild experience. I'm Tech 2 and a UTD Instructor, Nick's Cave 2 and Trimix 2, and Johnny is, well, Johnny - the dude's been everywhere.
We're a small, experienced team of open circuit divers. So far we've done a day of lecture and assembly, two days in the pool, and today was our first ocean dive.
What a crazy learning curve we're on. None of us had ever spent a breath on a rebreather, so it's all new, from concept to dive. But the configuration lends itself to us, since it's really a manual rebreather wrapped in a traditional DIR open circuit set of doubles.
And just to get this on the table, I'm completely biased, since I co-own UTD with Andrew and we're supporting this unit. So I'm not objective about the MC90, but I'm very objective about the training and the diving.
And that's been the really interesting part. At first, it's overwhelming. I'm pretty mechanical. I built an airplane in my garage, I've restored houses, and I actually like scuba gear, so the construction of the rebreather, and the modifications and options that make it into the MC90, fascinate me. Day one (and two, and three and four...) we work through the 47 point build checklist - a document that came as a result of weeks of work with Andrew, Leon from Innerspace, and UTD instructors Todd Powell and Andy Huber.
Once built (and unbuilt, and built) we took off for the pool. The class has 240 minutes of pool time, and we used every moment of it. There's enough time in those two days to calmly experience the newness of a rebreather, experience the sensitivity to buoyancy, and make all manner of mistakes. But it also gave us time to start to understand the procedures and the reasons behind them.
After two days of pool and video review, we went to the ocean. We'll do 240 minutes of skills in the ocean, then another 240 minutes of experience dives, 720 total minutes on the unit.
Today's ocean wasn't great...8 to 10 feet of visibility, lots of surge, but a pretty easy shore entrance. We spent the first hour at 50'/15m swimming around, then up to 30'/10m for skills.
This is a non-critical skills class...we do basic six, s-drills, valve drills, ascent drills. The basic six is modified from the open circuit basic six. With the MC90, it's CC to OC/OC to CC; switch from loop to long hose; modified s-drill; flooded loop drills; loop recovery; mask flood/mask remove.
After performing (and teaching) basic six a gazillion times on open circuit, this should have been easy, but the added procedures effect every skill, so today was about slowing down and thinking before every move. One of the great things about this class is we have six days in the water, so there's really time to go slowly. I've said a few times this week, "I have two speeds, and if you don't like this one, you really won't like the other one." We have the time to think through every move. The simple act of going from OC to CC involves about six steps - verify the COPIS is working, verify Oxygen is on, set the lung volume, set the PPO2, etc. so the ability to move slowly creates an education that seems to be working.
So with a whopping six hours on the machine, here are my impressions:
1. Anyone can learn this. The learning curve is crazy-steep, but it is filled with moments of insight that make the skills and procedures make sense.
2. Every moment I'm wearing the rig I'm grateful to have a set of doubles on my back and a bail-out valve at my chin. This concept has been the basis of countless internet discussions, and I'm not here to debate any of it, but what I now know about rebreathers (at least this one) is that there is one breath in the unit that goes back and forth between your lungs and the counterlung. If something goes wrong and that breath goes out of the closed system, then you have no gas in the system and you have to do something to get it back - add diluent, add oxygen, or bail out.
3. Bailing out works. Today, at 50 feet, as part of the skills I took off my mask. This is something I've done more times than I care to think about, and I've taught this skill a lot. I'm very comfortable without a mask. But somehow today some of the breathable gas in the rebreather escaped - I still don't know where it went (I'm new at this...give me a break, but I'm pretty sure I just breathed it out my nose), but the lung volume kept decreasing until I started to realize pretty soon I wouldn't have anything left to breathe. My choices - find the injector and add dil and hope that works, or bail out. Bailing out meant flipping a lever and I'm back with my old friend, open circuit. Take a moment to get organized, inject some gas into the counterlung, switch back to CC, and the whole thing was a non-event. But is was enlightening in two ways. One was that I realized how little gas is moving back and forth in the system, and how precious that gas is. The other is that you can bail out anytime for any reason with no workload to go to OC. No stage to find, and no chance to put an unbreathable gas in your mouth (like accidently grabbing the regulator from a 70 foot bottle at 100 feet). The diluent is bottom gas - it's always breathable. So with my little mask thing today I used about two breaths from the back gas - nothing really, but it made me calm and didn't effect the team. I'm not sure I'm explaining this perfectly well, but the whole experience gave me a great insight into how to manage the system. And remember, I'm biased, and this is the only rebreather I've ever used, but it works.
4. Let's see how the next four dives go, and I'll add to this list.
As a side note, UTD moved into a new facility last week in Carlsbad, California, about 20 miles north of San Diego. We have offices, a classroom, a warehouse, and a great little fill station. This was the first class we've run here, so there was a bit of chaos as we figured out how to work in the space, and Nick and John were amazingly helpful between RB setup, diving, and debriefing in helping us carve the new space into a fully functioning headquarters. Can't thank them both enough.
More to come,
Jeff Seckendorf
DAY 6 - So we're done. John, Nick, and I completed our experience dives today and we're now mCCR divers. It was a great day, with all of us way more comfortable on the rig. It was also great to just dive it and not have to deal with skills (there will be plenty of time for that).
We went in at La Jolla Shores, made a slow kick to 100 feet/30m to practice keeping the PPO2 at the target, then back up to 40', then 30, then 25, then 20, then 25, then 20, then 17, then quickly back to 20, etc. A gentle day designed to just get some time on the rig.
Overall it was a great experience. The team worked consistently well together, as three old dive buddies should. Andrew has taught this class enough now to know the limits of students coming in, and he created a really good balance of having us get used to the unit, then do skills. There were no critical skills...it's basically a recreational class, so it was all personal skills designed to get us to a point we can safely ascend and do a competent airshare with another MC90 diver or an OC diver.
One thing I'm completely comfortable with now is diving this in a mixed team. If someone comes up to me out of gas, I can do an s-drill in basically the same amount of time it would take on open circuit. And if for any reason someone has to assist me, the only real training they need is how to switch the lever on the bailout valve to go to OC. At that point I'll be in a traditional set of doubles breathing off the "necklace." Since the dil is bottom gas, it's always breathable.
The bottom line: I love this thing.
Jeff
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