MX-Z Sidemount rebreather class report
I thought I’d write up this class report for you guys since I’ve just taken the MX-Z mCCR1 class with AG. Actually it ran on a lot longer than expected so if it's too long to read then just watch the MX-Z intro video!
http://www.youtube.com/watch?v=ZLzIe...eature=feedlik
I knew I was heading over to rebreather at some point, but the thing I’ve found hardest to gauge was when to do it, right now I’m staying in mexico and have the time to get in the water and build up the hours on the unit which for me was going to be the biggest challenge, I often don’t dive in locations where I have either DIR type buddies, and when I do we rarely do the types of dive I’m going to need to do, to get up to speed with the rebreather for tech and cave in the future. Hanging round Cave Heaven in Tulum should give me that opportunity so I pulled the plug and went for it.
I’ve been diving quite a bit with rebreather divers in the past and I’ve known for a good while I’ll be heading this way at some point. So I’ve asked questions, poked about the units and in the end to choose a unit ended up being straight forward, it always had to be the MX KISS, or MX HH.
It must have a BOV, I wanted fully manual, so no leaky valves, no electronic injection. I know an eCCR can keep the PPO2 to within a tight range, but in reality I’ve been diving open circuit for years now where the gas changes PPO2 with depth, it’s never bothered me yet. I’m pretty sure I can keep it between 0.21 and 1.6 without help, particularly using standard gas mixes, so if you don’t need it why take it. I never really got the leaky valve idea as a safety backup, seems a bit like having a clock that counts 55 minutes in an hour, yeah it’s always injecting O2, and always the wrong amount.
The next consideration is on or off board bailout. Well for sure I want enough OC bailout for if the rebreather fails at maximum time from the surface, I’m used to diving doubles so lets just stick with that, flip the bail out lever and I’m back to what I know best. In actual fact to keep consistency for diving mixed team, and that from what we know about a CO2 problem you’re going to pound the gas we have the same rock bottom planning as OC.
So with that consideration I can hang the O2 on the left and I’m just diving as per a normal Tech 1 dive with a couple of extra bits. Now I could have built up another unit as a manual rebreather with offboard bailout, but that scalability from open water single tank rec diver right the way through to rebreather in the same equipment, only add what you need, to me is a large part of the DIR mindset. The same goes from single tank Z to sidemount rebreather. The UTD equipment configuration that I dive is 100% scalable and with this in mind the MX is the only system that is out of the box compatible with the my ideals. This was the most important point for me in moving to a rebreather and maintaining DIR Principals, once that Bail Out switch is flipped I’m back to Backmount doubles, or the Z-System and I have enough gas for my team and I to get home safely. Just that I now have to carry a plastic box full of magic sand back with me also, and to be honest if it’s sidemount I could easily just throw it away if it came to that. You have the same skill set, same equipment, same gas mix and same rock bottom.
While chatting to AG about ordering the system and organizing training he offered the choice of setting it up to be back/sidemount rebreather, the MX-Z. There’s a few different parts to order but, let’s go! I enjoy diving sidemount anyway, but having seen the video of the test MX-Z Meg in the pool I wanted to give that a shot for sure.
The first day was entirely equipment config and set up, there’s obviously a lot to do here. I’m going to start in backmount. There’s a frame with a standard set of doubles to set up in usual DIR fashion with 2 exceptions. I now have a diluent hose on the right post, and the necklace will be routed into the BOV. The rebreather just fits into the gaps. I’m using the KISS Classic canister, first things are that the O2 and Diluent injection to the head won’t be used, so they’re plugged, as are the ports for the counter lungs and OPV which is now on the counterlungs. The auto diluent valve is optional in backmount, though as it’s not used on sidemount or the other versions of the MX rebreather, I’ve plugged closed it to keep consistency. The loop used is now the same as the Hammer Head and Megalodon MX series, using the back mounted counter lungs with water trap/dump.
The next part is the neat little 36point checklist, quick and easy and takes no more that say.. all day! First time round of course but by the time I was ready to go home I had a rebreather that was ready to dive and a good idea of what all the buttons do.
Confined water sessions, started out in the morning and was back to the checklist to prep everything for the pool then dry runs, so relearning the basic 6 for the rebreather. It’s pretty close to OC, Switch from CC to OC and back. Bail out to the long hose. Lose and recover the loop. S-Drill, mask remove and replace then clearing water from the loop. I’m pretty glad it’s so similar as I was expecting a bit of information overload and didn’t fancy trying to remember a whole new set of skills while trying to just breathe.
Gearing up to get in the pool was the first time I actually had the unit on my back standing and I’m surprised how light it is, with a 12lb plate, the frame and a pair of steel 45’s it doesn’t feel any heavier than an average set of doubles.
So the first thing to do is get down to the bottom of the pool and get comfortable, the initial decent is on open circuit so nothing new, other than the fact my peripheral vision is occupied by a breathing loop. First impressions are that I’m straight into good trim and quite surprised by that. I was diving with UTDs Alpha as a wing, having used it before I know how stable it is anyway but I don’t think it’s just that. The rig is as balanced as a good long set of doubles and that’s the first preconception completely wrong on my part, I’m glad about it. I expected to initially be all over the place signaling to anyone looking at me ‘wind the windows down’ and fighting to stay horizontal for the whole course. There’s a bonus to start with!
Next thing is, still on Open Circuit the wing is quite well filled. The alpha has tri-glides on the side which can go onto the waist straps of the harness, if you fit it that way it drops the max lift down to just under 20Kgs. However it does keep the wing in very tidy when you don’t need max lift, helps with the trim and is then better able to dump in pretty much any attitude, when setting up I figured I wanted all the help I could get. Knowing how much buoyancy can be a pain with depth changes when overweight in shallow water on OC I figured I was in for a bit of a fight. I was blatantly heavy. So, check the O2 is on and has pressure. Check it’s connected via QC6, flip the lever and it’s a bit of a non event, the bubbles just stop.
Then it was 20 minutes of swimming around in a state of light to moderate frustration. PPO2, add gas to the loop, dump from the wing, add to the suit, is there enough gas in the loop? yeah cool, wait I’m moving again, add a bit to the loop, now it’s too full so out through the nose, start heading for the bottom, what’s the PPO2 again. Now gas in the feet, get rid of some from the wing. You get the picture. It was a lot to deal with, but less than expected really. PPO2 is straight forward to keep right so it’s just the case preempting what’s about to happen buoyancy wise and making tiny adjustments. Watching the video later it looked pretty calm and under control, I was working hard at it though.
The next day in the pool started off with again building the unit up from scratch, no complaints there as obviously this is one of the big things to get familiar with, In the pool again we started with buoyancy and swimming about, the first change is that from yesterday I can now have some sort of idea what’s about to happen when I switch to the loop, day one was a bit of a coin toss. I must’ve been a bit over confident though as the first couple of switches back to the loop during the basic 6 caused some buoyancy issues, it’s all lessons to learn. We then added a valve drill to the skills set, and it’s no big deal. The variation being that since you don’t have the longhose in your mouth to start with you need to purge it down after shutting the right post. Finishing up again with playing around in the pool, buoyancy was getting more natural still and I left the water pretty happy being able to hold stops at 9’ ,6’ and 3’ when I wasn’t focusing on drills and had a good fixed point of reference.
So now it’s time to switch over to sidmount. It’s just a case of pull off the counter lungs, BOV and canister and fit to the Z-Harness. In actual fact taking a standard set up Z-system, there are only 2 hoses to change over on the manifold, the necklace hose needs to now match the loop length and go to the BOV, and we need to add one more from the manifold to the diluent injector. Everything is 100% scalable here, you could lend your z-system to a buddy for an open water course, change 2 hoses, add a loop and counterlungs and have your rebreather ready to dive 15minutes later.
This is lightweight, I wasn’t sure I’d be able to descend. I’d say lighter than a single tank setup with an AL80 on your back. O2 and power inflator sit one above the other rock solid on the left, so if you’re used to diving the Z anyway the muscle memory is already there, I had a little more issue finding the Diluent and need to secure it better to the harness and get used to using it. In the water I had actually had plenty of weight and got down to the bottom and in position on OC. So the usual checks done and switch over to CC for a bit of a swim about. You cut absolutely no profile here, I think I might need to add a dorsal fin or something, because turn sideways, and you just keep going sideways! This is an awesome way to dive. So at the end of the day we made a couple of changes to tidy up what was spotted in the pool and now ready for some real diving!
The first open water dive was La Jolla Shores, for this sort of dive the difference between Back and Side-Mount is less pronounced. I went Side-Mount. Gearing up is going to similar anyway as you need the weight to sink those heavy undergarments but really as far as it goes in the water I prefer the freedom of sidemount, I didn’t need more than the 40 for bailout, and 6cu.ft of O2 so why take it.
This is really when it first really felt intuitive, out of the confines of the pool and swimming along, proper diving! We cruised on down to 60ft and hung about for an hour before on the wall following the hard bottom up in toward the beach. On the bottom was the first time I had to make control the injection a bit to maintain 1.2 PPO2, with Nx32 as diluent then it will run slightly low so it took a slight touch of the O2 button every now and again to keep it right. In the dark water there hud is bright, and I didn’t find the need to fixate on it. On ascent I have a close eye on by depth anyway and having the predator as a bottom timer with PPO2 right there then everything is right in your face. There’s a bit to think about here, but adjusting the PPO2 on ascent by exhaling through the nose and adding O2 is kind of controlling your buoyancy for you so it doesn’t end up as challenging as it might at first seem. It’s a busy job for sure and I don’t think I’d be ready to attempt a free ascent on CC just yet, it’s all small steps.
So back to the shop for new sorb and a clean.
The next couple of dive were just gaining the hours experience diving to be safe out there on my own. We were back at La Jolla hanging out on the wall over the weekend, a bit of bad weather had just come in which got rid of the red tide and opened the place up to some great viz for my final dive. Gearing up had just got easier and easier over the week and diving the unit was more natural every day. The checks and pre-breathe just took a few minutes and those initial thoughts from the pool of not appearing to do anything and going up and down for no reason have gone, and I’m happy just hanging around in midwater. After an hour I’d used barley a dribble of diluent and about 1 cu.ft of O2 and really could have stayed down there all day.
At the end of it all this course has surprised me, my expectation was that I would finish up the course then head back to mexico to spend the first bunch of dives holding onto the Dil and O2 injectors while focusing on the PPO2. Then re-aquire myself over the next couple of months with mexican aquatic life while I get properly comfortable with the system, I saw it as a complex tool to do the dives I plan on doing in the next few years. The reality is that once I get back from dema I’ll be setting up sidemount and be on every boat trip I can get someone to come along, diving and loving it from the outset. The weight of a single tank setup and limitations being NDL, or the sun going down is off the charts.
Dave
