missionmtb
Contributor
I first heard about this rebreather after going down a rabbit hole on various homebuilt units. After years of researching rebreathers like this from the very popular Triton, O2ptima CM and FX-CCR to more obscure units like the White Arrow Sweet Deco, I knew this was a form factor that would open up new options for me in my diving. I also looked at sidewinder-style units and have a feeling this will be my next form factor, maybe in addition to the GBM...
Note: I purchased this unit with my own scratch and have no affiliation with the manufacturer. These opinions are my own and may be in error.
Background.
I am a reasonably long time rebreather diver, having done the vast majority of my diving closed circuit. This is my 3rd unit after a Poseidon mkVI/Se7en and an ISC Tiburon eCCR. I dive in a lot of environments but do the majority of my diving locally off charter boats and shore. A few times a year I'll pack my CCR in a carryon and head someplace. As I dove my last unit more and more (Tiburon) I found that I wanted something lighter and easier to get into. I also wanted something that was manual or hybrid out of the box as I had modified my Tiburon with a solenoid from a ReVo hCCR. I came to prefer this configuration for its smooth oxygen addition and consequently solid buoyancy at a given depth. Though the hCCR was great I started to go up against the limitations of a CMF and was looking at simple, depth independent options. Something more like a needle CCR (nCCR).
GBM configuration.
Enter the GBM! I bought the 'TEG' configuration that offers solid state sensing, dual 4 pin connectors and some other niceties concerning gas connections. There is also a 'TEC' version and a 'REC' version but I'm willing to bet the majority of units sold will be TEG. I won't try to explain the different versions, better just to check out the site which comes up pretty easily via google. The Petrel 3 and NERD 2 were options to add for the TEG. I also swapped my Perdix AI for a new Petrel 3 SA to round out the compute suite.
I immediately canned the clips at the top of the unit and added fixed bolt snaps. I also got rid of the SPG and HP tree in favor of just a Swift transmitter.
Other than that the unit is stock.
I didn't end up going with either the wireless handset or HUD, but may try this in the future. A little bit of sticker shock as well as comfort with Shearwater wired units decided this for me.
Why I swapped stuff.
Bolt snaps just seem a little more solid (even though I dove a DR Transplate harness with them with no complaints). I've also dove for a long time with just transmitters without issue and am prepared to deal with dropout should it occur.
What I love.
Size - Holy smokes it's tiny. The bag itself measures about 13" (33 cm) square on its front face and about 6" (15 cm) thick and the little faber 2L doesn't add much to it dimensionally. The loop hoses are about 13" (33 cm) long as well. To give you an idea of what a game changer this is, I can fit my entire rebreather and bailout regs in my personal item when flying and save the carryon entirely for camera gear! I've made a shoulder strap out of some 2" webbing, neoprene and D-rings to carry it around messenger bag-style. Awesome! Without scrubber or a bottle the unit is about 15 lbs. (6.8 kg). Scrubber material adds about 5 lbs (2.2 kg) and the faber adds about 10 lbs (4.5 kg) for a ready-to-dive total of about 30 lbs (13.5 kg).
SSS - The solid state sensors from Oxygen Scientific are excellent! Rock solid, fast and basically immune to condensation. Incredible!
4 pin interface - no longer am I tied to a single unit with my 4 pin computers. I can swap them to whatever mCCR I have provided the cable is long enough...
Build quality - everything is really solid. The bag is made of the same or very similar material to the Dive Rite super fabric. All of the major components are machined from solid delrin. The baseplate is a sandwich of two thick aluminum plates anchoring the whole unit. I was worried about the counterlungs being fragile but so far they've been really solid as well. They have a p-port style connection to the canister a la drager and poseidon-style connection to the loop.
Gas block - it's great. The needle valve works as advertised and is intuitive to adjust. The MAV buttons, though neither recessed, are easily distinguished from one another. It's nice to have everything located in one place, accessible with either hand. I don't expect to see any issues at big depths as the delrin wall thickness is really beefy (stayed tuned).
Needle valve - want to descend quickly and add zero oxygen in the process so you use less DIL at depth? Dial it back. Working hard? Dial it up. On the surface and don't want to waste gas but also don't want to depressurize your hoses? Dial it down. So sick.
Cost - at the end of the day it was pretty reasonable. I was able to sell my 4 year old Tiburon and buy the GBM with training and come out basically even. You can forego the SSS and find some cheaper computer options to save a little more dough.
Loop route - I have never been able to see my environment with this little obstruction since getting into rebreathers. The loop hoses don't obstruct my vision at all and stay down there below the DSV. Because I have my unit hiked way up they loop outward away from my chest and are basically invisible. Another awesome benefit of this loop route is I can put my long hose around my neck and deploy it without messing with my loop at all!
Simplicity - because there are no electronics inside the head/canister, if you have something catastrophic happen it'll likely just cost you a wire harness and sensors. All of the parts are relatively inexpensive on their own and user replaceable. Feels like a proper field serviceable unit.
What’s not so great.
2 SSS / 2 Galvanic - the solid state and galvanic cells behave very noticeably differently as far as response time and calibration. I will definitely be adding at least one additional solid state sensor for the 3 on my NERD
WOB - Coming off of two units that are (IMHO) the best breathing units available today (in proper trim) the breathing stinks. In proper and modified trim (slightly head up) the unit requires a bit of extra push to exhale and basically no effort to inhale. The resistance to exhale improves substantially as you hike the unit up your chest, but this has the downside of blocking the drysuit valve. I'm already getting used to this and I think it's just a function of the mounting style. Oddly enough, almost all other positions (head up, inverted, on your back, on your sides) breath better than OTS counterlungs for me... Some of my trouble may also be that I'm still learning what it feels like to be at minimum loop so I may be fighting overinflation at times. We'll see.
Underwater weight - the unit is neutral at 3/4 full counterlungs and positively buoyant with full counterlungs. I wouldn't mind a stainless steel mount plate if it could make the unit neutral at full lung. This buoyancy results in the need for a little more lead because the unit is not helping in that department. Is this a con? Not sure.
Teething issues - I have an earlier serial number unit so we had to work through some things. None of the issues I experienced were due to design or workmanship so I'll leave it at that.
Diving the unit.
Putting on the unit is a breeze. Clip it on and go. I miss having the DIL integrated into the unit for pre-dive but I'll get used to it. I never want to put another backmount harness on again now that I'm diving the XDEEP stealth, sooo comfortable. Putting your side cylinders on is a breeze too. I'm still trying to decide what order is right for me to clip my bottles before or after the GBM is on, but either has worked pretty well. To futz with your cylinders you can unclip the bottom clips on the GBM and float the unit so your arms are totally free. Lovely.
Once you're diving the unit sort of disappears. It's out of your eye line and you have nothing on your back. You feel almost naked... I can get through the tiniest little holes with the unit and I'm working up to trying to get thru actual restrictions in superman with the unit over my head. Keeping off the bottom a little further to account for the unit takes a second to get used to, but it's not that much. Less than a foot for sure. What's great about it is there's no getting hung up on something you can't see like in back mount. If the GBM or a cylinder snags on something it's in front of you and easy to deal with.
Post dive is like any other unit but is just that little bit nicer because the unit separates so easily from your BC.
-missionmtb
Note: I purchased this unit with my own scratch and have no affiliation with the manufacturer. These opinions are my own and may be in error.
Background.
I am a reasonably long time rebreather diver, having done the vast majority of my diving closed circuit. This is my 3rd unit after a Poseidon mkVI/Se7en and an ISC Tiburon eCCR. I dive in a lot of environments but do the majority of my diving locally off charter boats and shore. A few times a year I'll pack my CCR in a carryon and head someplace. As I dove my last unit more and more (Tiburon) I found that I wanted something lighter and easier to get into. I also wanted something that was manual or hybrid out of the box as I had modified my Tiburon with a solenoid from a ReVo hCCR. I came to prefer this configuration for its smooth oxygen addition and consequently solid buoyancy at a given depth. Though the hCCR was great I started to go up against the limitations of a CMF and was looking at simple, depth independent options. Something more like a needle CCR (nCCR).
GBM configuration.
Enter the GBM! I bought the 'TEG' configuration that offers solid state sensing, dual 4 pin connectors and some other niceties concerning gas connections. There is also a 'TEC' version and a 'REC' version but I'm willing to bet the majority of units sold will be TEG. I won't try to explain the different versions, better just to check out the site which comes up pretty easily via google. The Petrel 3 and NERD 2 were options to add for the TEG. I also swapped my Perdix AI for a new Petrel 3 SA to round out the compute suite.
I immediately canned the clips at the top of the unit and added fixed bolt snaps. I also got rid of the SPG and HP tree in favor of just a Swift transmitter.
Other than that the unit is stock.
I didn't end up going with either the wireless handset or HUD, but may try this in the future. A little bit of sticker shock as well as comfort with Shearwater wired units decided this for me.
Why I swapped stuff.
Bolt snaps just seem a little more solid (even though I dove a DR Transplate harness with them with no complaints). I've also dove for a long time with just transmitters without issue and am prepared to deal with dropout should it occur.
What I love.
Size - Holy smokes it's tiny. The bag itself measures about 13" (33 cm) square on its front face and about 6" (15 cm) thick and the little faber 2L doesn't add much to it dimensionally. The loop hoses are about 13" (33 cm) long as well. To give you an idea of what a game changer this is, I can fit my entire rebreather and bailout regs in my personal item when flying and save the carryon entirely for camera gear! I've made a shoulder strap out of some 2" webbing, neoprene and D-rings to carry it around messenger bag-style. Awesome! Without scrubber or a bottle the unit is about 15 lbs. (6.8 kg). Scrubber material adds about 5 lbs (2.2 kg) and the faber adds about 10 lbs (4.5 kg) for a ready-to-dive total of about 30 lbs (13.5 kg).
SSS - The solid state sensors from Oxygen Scientific are excellent! Rock solid, fast and basically immune to condensation. Incredible!
4 pin interface - no longer am I tied to a single unit with my 4 pin computers. I can swap them to whatever mCCR I have provided the cable is long enough...
Build quality - everything is really solid. The bag is made of the same or very similar material to the Dive Rite super fabric. All of the major components are machined from solid delrin. The baseplate is a sandwich of two thick aluminum plates anchoring the whole unit. I was worried about the counterlungs being fragile but so far they've been really solid as well. They have a p-port style connection to the canister a la drager and poseidon-style connection to the loop.
Gas block - it's great. The needle valve works as advertised and is intuitive to adjust. The MAV buttons, though neither recessed, are easily distinguished from one another. It's nice to have everything located in one place, accessible with either hand. I don't expect to see any issues at big depths as the delrin wall thickness is really beefy (stayed tuned).
Needle valve - want to descend quickly and add zero oxygen in the process so you use less DIL at depth? Dial it back. Working hard? Dial it up. On the surface and don't want to waste gas but also don't want to depressurize your hoses? Dial it down. So sick.
Cost - at the end of the day it was pretty reasonable. I was able to sell my 4 year old Tiburon and buy the GBM with training and come out basically even. You can forego the SSS and find some cheaper computer options to save a little more dough.
Loop route - I have never been able to see my environment with this little obstruction since getting into rebreathers. The loop hoses don't obstruct my vision at all and stay down there below the DSV. Because I have my unit hiked way up they loop outward away from my chest and are basically invisible. Another awesome benefit of this loop route is I can put my long hose around my neck and deploy it without messing with my loop at all!
Simplicity - because there are no electronics inside the head/canister, if you have something catastrophic happen it'll likely just cost you a wire harness and sensors. All of the parts are relatively inexpensive on their own and user replaceable. Feels like a proper field serviceable unit.
What’s not so great.
2 SSS / 2 Galvanic - the solid state and galvanic cells behave very noticeably differently as far as response time and calibration. I will definitely be adding at least one additional solid state sensor for the 3 on my NERD
WOB - Coming off of two units that are (IMHO) the best breathing units available today (in proper trim) the breathing stinks. In proper and modified trim (slightly head up) the unit requires a bit of extra push to exhale and basically no effort to inhale. The resistance to exhale improves substantially as you hike the unit up your chest, but this has the downside of blocking the drysuit valve. I'm already getting used to this and I think it's just a function of the mounting style. Oddly enough, almost all other positions (head up, inverted, on your back, on your sides) breath better than OTS counterlungs for me... Some of my trouble may also be that I'm still learning what it feels like to be at minimum loop so I may be fighting overinflation at times. We'll see.
Underwater weight - the unit is neutral at 3/4 full counterlungs and positively buoyant with full counterlungs. I wouldn't mind a stainless steel mount plate if it could make the unit neutral at full lung. This buoyancy results in the need for a little more lead because the unit is not helping in that department. Is this a con? Not sure.
Teething issues - I have an earlier serial number unit so we had to work through some things. None of the issues I experienced were due to design or workmanship so I'll leave it at that.
Diving the unit.
Putting on the unit is a breeze. Clip it on and go. I miss having the DIL integrated into the unit for pre-dive but I'll get used to it. I never want to put another backmount harness on again now that I'm diving the XDEEP stealth, sooo comfortable. Putting your side cylinders on is a breeze too. I'm still trying to decide what order is right for me to clip my bottles before or after the GBM is on, but either has worked pretty well. To futz with your cylinders you can unclip the bottom clips on the GBM and float the unit so your arms are totally free. Lovely.
Once you're diving the unit sort of disappears. It's out of your eye line and you have nothing on your back. You feel almost naked... I can get through the tiniest little holes with the unit and I'm working up to trying to get thru actual restrictions in superman with the unit over my head. Keeping off the bottom a little further to account for the unit takes a second to get used to, but it's not that much. Less than a foot for sure. What's great about it is there's no getting hung up on something you can't see like in back mount. If the GBM or a cylinder snags on something it's in front of you and easy to deal with.
Post dive is like any other unit but is just that little bit nicer because the unit separates so easily from your BC.
-missionmtb
