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boriss

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First of all, a huge thanks to Ben Lair from Paragon Dive Group (@DiveTucson ) for helping me test the rEvo and Choptima today!

Keep in mind, I'm still a newb, so take what I write below as just personal notes for myself; which shouldn't be used as any type of authoritative information for comparison, etc.

Yesterday Fathom did a try dive, which I've been looking forward to for months. Charlie, the owner of Fathom, did a complete build from start to finish at which point we had a choice of diving a "cave" or a "tech" setup. Cave setup being lighter, more compact, with the DIL/BO being offboarded (side-mount). While the tech rig (assembly of which is pictured below) has DIL/BO in the form of dual LP50's attached directly to the CCR.

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I wanted to try the tech setup, as that's most likely the configuration I'd choose diving off of a boat, but as I knew I'd be testing other units, I wanted to be fair to Fathom and not unfairly compare such a heavy/loaded rig to lightweight setups.

We were given some instruction on how to dive the CCR and under Charlie's and Jon Bernot (Instructor Trainer and owner of Cave Country Dive Shop) we descended to the 20ft platform at Blue Grotto and swam/experimented at that depth for about 20-minutes, then we went down to the 35ft platform, swam around there for another 12-minutes and then slowly made our way back up. Total dive length was 36 minutes and was my first time ever trying a rebreather. What an experience!! I'll save the details of learning how everything works, but as everything is manual, there were no nannies doing things for me. Had to learn quickly!

The unit instantly trimmed out perfectly and once I figured out how to establish proper loop volume I was able to breathe properly. I also played around with the needle valve and quickly dialed it in for my gas consumption. Our goal was to hold a ppo2 of 1.3 and after initially overshooting it a bit, I dialed it back and found a sweet spot which landed me at 1.3 without touching the O2 MAV. It also took at least 15-minutes to dial in buoyancy to a point where I wasn't constantly kicking to maintain it.

My thoughts are that it's a very nice unit with high quality parts and high degree of craftsmanship. The unit can be configured in a ton of different ways and no detail is overlooked. Up to a 9lb radial scrubber, fully potted electronics, BMCL, BOV w/DILOUT, etc. The Fathom HUD is amazing!! In trim the WOB is phenomenal, but head down it was harder. I thought head movement was a little restricted and wasn't sure if it's because of the BOV (hose) or just being new to CCR. In general, anyone looking for the highest quality manual CCR can't go wrong with this unit.

Here's what I dove:
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Today I met up with Ben Lair (@DiveTucson) in Ginnie Springs, who offered to let me try dive his Optima CM (Choptima) and my buddies rEvo Mini. We started with the rEvo. We replaced the steel tanks with aluminum and I pulled out all the weight from the upper pouch. I didn't need the additional weight with my wetsuit. We set the setpoint to 0.7 (just in case), but my goal was to maintain a 1.0 and fly manually. Similar to the Fathom, the unit instantly trimmed out well, the breathing was very good but slightly different and unlike the Fathom the WOB was more consistent whether I'm pointing straight up or down. There were a lot more noises and just like the Fathom I had to essentially learn how to dive this unit. ADV on it is disabled. The overall package was relatively light on my back and I carried an AL72 for BO.

I really like the overall all-in-one package, super easy to set up, no extraneous hoses, connections, T-pieces, etc. Very clutter free, put on and go. The range of motion seemed better here.

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Last, but not least, we attached Ben's Choptima to my double HP100's.... not quite the standard config, but that's one of the beauties of Choptima... add it to whatever you want. Ran it with just a NERD, no wires or computer on the wrist - felt almost naked for a minute there, but the NERD is super nice!

Choptima had an ADV on/off, so I got to experiment with that. After a few minutes of back/forth I believe I prefer that to be off - allows me to better manage loop volume and doesn't screw up my buoyancy without me knowing. The Choptima breathes well but is the complete opposite of the rEvo. It was harder to exhale and easier to inhale. In fact, I always felt like the gas was rushing into my mouth (chipmunk cheeks), but I'm certain that's just because I don't know how to maintain ideal loop volume, etc. Similar to the rEvo, it was a little more consistent in WOB in various orientations, but obviously going inverted it breathed more like a rEvo. I understand what people mean about chest clutter now, but also believe that's something I'd be used to. I noticed when hovering just a few inches off the bottom at times I'd feel the bottom (not used to the additional equipment there). Didn't have issues with trim with this unit either, but I definitely felt a little pregnant. Was very interesting to feel the lungs expand and contract as I breathed in and out. Last but not least, (I believe) it seemed to give my head the most range of motion.

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So all-in-all, an excellent adventure! I learned a lot. CCR diving is hard!! I spent 1.5-hours in the water on three different units and I still had the reflex to try and inhale to slow descent and exhale to slow ascent, etc. Will have to completely relearn how to breathe and how to maintain buoyancy. I'm able to dial it in just right but you move a couple of feet up or down and everything changes. Much more sensitive than I thought it would be, but it could be just me :)

Regarding the units, they were all great and it's clear that the unit should be chosen based on the manufacturers philosophy (matching divers') and ultimate mission. I'm very torn about which unit I'll get, but one thing I learned is I definitely prefer eCCR - at least at this stage. When I hot-drop to a deep wreck I really want an ADV and for the computer to maintain my ppo2, at least until I get to the wreck, then I can fly manually if needed. I definitely like the NERD, the information is just all right there without obstructing my vision. I reserve the right to do a complete 180 in the future, after I actually learn how to dive properly :)

Now I just need to figure out what I value more:
rEvo - an easy to maintain unit with no clutter, easy to don and jump off a boat and separate BO, or
Choptima - easy to travel, can be added to any type of diving I may choose to do in the future, etc

There are many more pros/cons I didn't list... this isn't meant to be a comparison of the three units. As I said before, I'm not qualified to compare anything at this point. I'm sure when I get more experience the things I'll be comparing (or caring about) will be completely different.
 

GDHLEWIS

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Sounds like you had some fun trying out the various equipment. Good little write up for people who have little to no knowledge on rebreathers. Gives a little idea on what to expect...well it did for me.
 

sprockjohnson

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Excellent write up! I dive a rEvo, a Sport KISS, and a Drager and they are all different in their WOB and how they feel on the back. I have been eying the Choptima for a bit now and was definitely interested in your observations regarding the chest clutter and WOB.
 

rddvet

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You’re going about it right by trying a few. I will tell you that even with multiple test dives you’ll basically be making a mostly blind choice because you really won’t know what you like until 30+ hours of really diving a unit. I’m partial to the fathom because I own 3 and love mccr. I’m not an eccr fan at all. So that played. A big part in my decision. Choptima is interesting to me. Revo is a no go unit for me. One thing to highly consider is customer service. If you’re in Florida you will get exceptional service from Charlie at fathom and from dive rite.
On the adv: they are great for getting to depth quickly. But an adv does add more failure points and ,ore importantly if you’re doing deep stuff, an adv can get you in trouble if you aren’t insuring you’re hooked to the right gas
 

Johnoly

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I spent 1.5-hours in the water on three different units
That's a fantastic opportunity to test dive 3 units instead of the usual 'just 1'. I understand it's a first time intro dive and can't check off all the boxes. This is a great writeup you did so others can get just a peek if they are considering a switch to a rebreather. Thanks !!
 

AustinV

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I'm surprised you felt the WOB was limited on the Fathom in certain positions, I tested a Fathom last year at Dutch Springs for one of Charlie's demo days and I found it breathed well in all positions I was able to get into (there is so much I have read about certain CCRs not breathing well in certain trims so I wanted to check).

That being said it is the only CCR I have tried so I don't have anything to compare it to. I too dove it in the "cave" setup with sidemounted DIL/BO. I was definitely impressed with the build quality and ease of setup. The needle valve was easy to tweak, even with gloves on, and even with zero previous ccr experience I was able to get it right where it needed to be. HUD was really nice, I haven't used a NERD but almost feel like it would be overwhelming. Look forward in the future to trying out a few more units, definitely fun to try/learn. And yes - I also found myself several times taking a deep breath to slow descent only for nothing to happen, that will take some getting used to!
 

rddvet

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I'm surprised you felt the WOB was limited on the Fathom in certain positions
I wasn't going to say it initially because I didn't want to offend the OP, but I believe that is more about lack of experience than anything else. The fathom's WOB is amazing. I actually initially thought the WOB wasn't great(it was my first unit) until I tried several other units and realized it was my lack of experience to compare to more than anything else.
 

Manatee Diver

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But an adv does add more failure points and ,ore importantly if you’re doing deep stuff, an adv can get you in trouble if you aren’t insuring you’re hooked to the right gas

The ADV was one of the things I hated about the Optima on the try dive I did. I didn't realize it at the time, it wasn't until I described about what I liked about the Fathom, and disliked about the Optima that someone put two and two together for me.

So when I finally buy a unit the ADV is probably the first thing to go, or at least set to such a low level that if I trigger it I let the loop volume get WAY too low.
 

Marie13

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The ADV was one of the things I hated about the Optima on the try dive I did. I didn't realize it at the time, it wasn't until I described about what I liked about the Fathom, and disliked about the Optima that someone put two and two together for me.

So when I finally buy a unit the ADV is probably the first thing to go, or at least set to such a low level that if I trigger it I let the loop volume get WAY too low.

My Spirit has a ADV. Definitely breathes better when I’m relaxed and taking deeper breaths. At first it was horrid during training!
 
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