Review Course Report: Fathom Mod 1

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Blackfrogfeet

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Location
Canada
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A few (many) months ago I started the thread "Fathom vs KISS Classic", which ultimately ended in one or two users asking for an update on what I ended up doing and how it went. Well here it is.

Background:
I was an OC hypoxic trimix diver (mostly GUE trained) looking for a CCR option that had BMCLs, produced in North America, was lightweight, modular, and would be easy to configure with backmounted 50s so I could be compatible with a lot of the GUE JJ guys I dive with. My search led me to the Fathom.

I took a 6 day Mod 1 program with Advanced Recreational Trimix Plus (51m max depth, minimum dil O2 18%). The course was run out of Third Dimension with Kelvin in Tulum and there were 2 students in the class including myself. Both of us were using the Fathom with onboard LP50s/Lola in the tech rig, BOV with no ADV. Standard gases were used as dil

The Class:
Day 1 was theory, followed by 5 days of diving. The first day was essentially 150 minutes of swimming around in 6m of water at Casa Cenote, developing buoyancy and some skills (valve drill, SMB deployment, S drill, BO). I found maintaining buoyancy in this range agonizing at first! The next 2 days were spent at Cenote Orcheidea in the 10-20m range. Here we swam circuits while practicing maintaining PO2, dil flushes, BOs, and buoyancy throughout constant depth changes. We also kicked the frequency of the drills up. The last 2 days were spent on the reefs off of Akumal where we dove from a boat. Again, the task loading was increased by adding blue water ascents, as well as valve failure resolutions on the Lola. We totaled 12 hours underwater.

Takeaway:
I felt the class was very well done. The task loading was increased in manageable but challenging increments each day. I left the course feeling very confident about using my new machine in my home waters without supervision. The other student and I were also at different levels in our diving, but Kelvin had a way of getting each student to perform to their maximum without getting in the other's way.

This was my first time in Mexico and it really made me change my mind on the importance of training in your home environment vs traveling to train. I now think being somewhere warm where the logistics is good makes learning much easier and pays dividends in the end.

In terms of the rebreather, I'm very happy with my choice (although every new rebreather diver says that about every unit). I found the needle valve and MAVs very easy to use and intuitive. Its very simple and robust, and I think it will serve me well on my future adventures.
 
Very cool. I believe we were his first or second students on the unit. We did Casa, no reefs. That would have been cool. We did a day at Angelita and I learned quickly how bad my buoyancy was my first couple days on the rebreather. We'd hover over the sulfide layer and I'd slowly sink into it. I'd try to fix it and I'd get too shallow and vice versa until I was thoroughly angry with myself.
I've got about 100 dives on the unit since taking the class 3 years ago and not a single issue with the unit (hopefully I didn't jinx myself for this weekend). Unit is easy to dive and is configurable for what you want to do. I mostly dive sm bailout. My wife exclusively dives onboard 50s. We both have ADVs. I love mine and don't want to give it up, she could care less about hers (ADV that is). It appears most of the fathoms people are buying nowadays are without ADVs. I'm just very used to it and don't know if I'd like not having it.
 
This was my first time in Mexico and it really made me change my mind on the importance of training in your home environment vs traveling to train. I now think being somewhere warm where the logistics is good makes learning much easier and pays dividends in the end.
There is definitely value in doing 12hrs in 5 days with bare hands so you can feel what you're doing vs 6 hrs in 5 days with drygloves and (still) frozen hands. I'm a "train how you dive" guy too - but when you're starting from zero the warmer/easier conditions are a nice jump start.

I dive a fathom needle valve with a 200psi blocked first sometimes too (on a Kiss). I find it really nice. My biggest annoyance is keeping another blocked first around for long trips. When the DS4 fails (and it will eventually) there is nothing in your save a dive box that'll replace it except another blocked 1st stage. Although with the needle valve, it doesn't need to be the exact same IP at least.
 
This guy has great postage for DS4s too


Down the page is the XTX ADV I had him build for one of my homebuilts a few years ago

1644650513629.png
 
When the DS4 fails (and it will eventually) there is nothing in your save a dive box that'll replace it except another blocked 1st stage.

I'd be tempted to carry just a spare blanking plate--I haven't tried it yet, but I bet a DS4 blanking plate works on HOG/Deep6/DR and most of the other clones or derivatives. For that matter, my fixed DS4 was a Mexican special: the plastic pressure transmitter was just cut about 1/2" short and stuck back in.


Back to the main topic, great trip report!
 
I'd be tempted to carry just a spare blanking plate--I haven't tried it yet, but I bet a DS4 blanking plate works on HOG/Deep6/DR and most of the other clones or derivatives. For that matter, my fixed DS4 was a Mexican special: the plastic pressure transmitter was just cut about 1/2" short and stuck back in.


Back to the main topic, great trip report!
You can carry a pin spanner and the blanking plate will work in many diaphragms if you swap it out (although you'll become far more depth limited compared to the 200psi IP used in the stock fathom configuration). Of course assuming you have an extra ds4 or clone you can commandeer. It's easier and simpler to have a complete spare 1st - just annoying because they are so heavy and otherwise kind of useless.
 
There is definitely value in doing 12hrs in 5 days with bare hands so you can feel what you're doing vs 6 hrs in 5 days with drygloves and (still) frozen hands. I'm a "train how you dive" guy too - but when you're starting from zero the warmer/easier conditions are a nice jump start.

I dive a fathom needle valve with a 200psi blocked first sometimes too (on a Kiss). I find it really nice. My biggest annoyance is keeping another blocked first around for long trips. When the DS4 fails (and it will eventually) there is nothing in your save a dive box that'll replace it except another blocked 1st stage. Although with the needle valve, it doesn't need to be the exact same IP at least.
I just bit the bullet and bought an entire spare DS4, plug, and stiff spring from Martin. I live and dive in alot of very remote areas. Always nice to know you have a full spare. DS4's are small just chuck one in your backpack.


This guy has great postage for DS4s too


Down the page is the XTX ADV I had him build for one of my homebuilts a few years ago

View attachment 706627

Martin does amazing work. I had him build one for me also
1644668597125.png
 
I'd be tempted to carry just a spare blanking plate--I haven't tried it yet, but I bet a DS4 blanking plate works on HOG/Deep6/DR and most of the other clones or derivatives. For that matter, my fixed DS4 was a Mexican special: the plastic pressure transmitter was just cut about 1/2" short and stuck back in.


Back to the main topic, great trip report!

I don't waste my time typically carrying a backup blocked first. There's no reason you can't use any first stage. It will just dive a little differently. Rjack seems to be doing alot of deep exploration way out from civilization, so having an extra makes sense. I always have 1-2 spare regs with me for stages and whatnot, so if an issue pops up I steal one of those.
Martin at tecme makes a blanking plug for the scubapro diaphragm reg, which obviously also works in the halcyon regs which are cheaper. So I've been slowly moving alot of my ccr regs over to those. The only negative is the lack of the stronger spring, but I'm not doing 200+ foot dives that would require it.
 
The only negative is the lack of the stronger spring, but I'm not doing 200+ foot dives that would require it.

Other option that I do when I max out my IP is just set my unit up to have an offboard plug for o2 that is plumbed into the MAV side then you just dive the unit in full manual mode. Omniswivel with checkvalve works great.

1644702331867.jpeg
 

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