Question Trying to decide on a rebreather unit

[rjack321]

With large bailouts, maybe with more than two ali80s, the chest area will become mightily crowded.

Backmount keeps the box with your three smaller cylinders (oxygen, diluent and drysuit air) behind you so your front and sides can be cluttered with bailouts.

Same issue with SM.

Large BOs, 1,2,3 deco gases, suit gas, suit heat, light(s) you RAPIDLY run out of sides (or chest) for your sidemounts and look like a Christmas tree. At that point you might as well use some of that wasted space on your back - coming full circle to backmount as the best and/or only quasi-clean configuration for the job.

 

[BoltSnap]

With large bailouts, maybe with more than two ali80s, the chest area will become mightily crowded.

Backmount keeps the box with your three smaller cylinders (oxygen, diluent and drysuit air) behind you so your front and sides can be cluttered with bailouts.

Same issue with SM.

Large BOs, 1,2,3 deco gases, suit gas, suit heat, light(s) you RAPIDLY run out of sides (or chest) for your sidemounts and look like a Christmas tree. At that point you might as well use some of that wasted space on your back - coming full circle to backmount as the best and/or only quasi-clean configuration for the job.

So, one can say chest mount for travel and less heavy duty deep diving? A Suburban vs. Trailblazer?

 

[rjack321]

So, one can say chest mount for travel and less heavy duty deep diving? A Suburban vs. Trailblazer?

I've done significant deep diving in a sidewinder 80+m in cold water (4-5C) and its definitely "ugh" and not nearly the seemingly graceful unit you see in the marketing materials diving a set of lp50s as dil/bo with no suit gas, no suit heat, no deco gas.

I don't have a chest mount unit and never dive one. But for any significant deep dives with either SM (or CM) you spend all this time and energy to move stuff off your back and instead that gear is forced to hang everywhere else - honestly for no good reason cause you're not sleek nor graceful anyway.

 

[BoltSnap]

I've done significant deep diving in a sidewinder 80+m in cold water (4-5C) and its definitely "ugh" and not nearly the seemingly graceful unit you see in the marketing materials diving a set of lp50s as dil/bo with no suit gas, no suit heat, no deco gas.

I don't have a chest mount unit and never dive one. But for any significant deep dives with either SM (or CM) you spend all this time and energy to move stuff off your back and instead that gear is forced to hang everywhere else - honestly for no good reason cause you're not sleek nor graceful anyway.

I am considering the XCCR as my top choice but that BM unit is going to be a bear for travel. Not sure if you can easily convert the same unit between BM and CM for travel and local.

 

[lostsheep]

Full disclosure up front , pun intended, I’m a chop guy.

Claiming the chop is inappropriate for deep dives is BS. I agree fully that the chest clutter is real, but after ~3 years diving mine I maintain it is a manageable problem. You learn to deal with it. By that I mean you don’t reach across your chest to hit the MAVs. You can but you MUST be extremely careful as the wrong technique can hit the MAV you didn’t intend.

IMO, deep dives mandate carrying lots of cylinders and lots of gas, there just isn’t a way to avoid this. Utilizing the space on your chest is just as valuable as utilizing the space on your back or your sides. I dive BM doubles and SM with my chop. For deep dives I use all 3 locations with cylinders of appropriate volume.

I always reserve the right to be FOS but I can’t think of another form factor that makes carrying 4 full size cylinders easier WITH a CCR than a chest mounted unit. Further, the ability to scale volumes easily is unmatched. I can throw BM doubles with SM cylinders on very easily because I am accustomed to diving either. 2 deep BM doubles on my back with 2 SM deco bottles and the chop is WAY more rope than I need to hang myself; that’s before I start clipping tanks to my butt D.

 

[rjack321]

I am considering the XCCR as my top choice but that BM unit is going to be a bear for travel. Not sure if you can easily convert the same unit between BM and CM for travel and local.

Yeah not sure what to suggest. There really isnt one unit that rules them all

I started 8-9yrs ago with a backmount meg 2.7 and still use it for ocean and great lakes dives. About 5-6 years ago I bought a sidewinder, did a crossover and for me it's definitely "cave only" (or sometimes shore diving in a lake for practice). I have done a few 60m+ dives on it and honestly even being able to drop deco gasses in the cave it's still a messy dangly challenge in cold water. I would not want to use it on a 75m ocean dive with 2 deco gasses, suit gas, suit heat etc.

 

[RedSeaDiver2]

I am considering the XCCR as my top choice but that BM unit is going to be a bear for travel. Not sure if you can easily convert the same unit between BM and CM for travel and local.

Depends on which airline and your frequent flyer status. My airline of choice gives me a luggage allowance of 3x 32kg

 

[broncobowsher]

My thoughts, going back to the original post.
Skip the sidewinder, it's not the same as sidemount OC that you are thinking of.
I'll add rEvo as there is a strong rEvo community in southern California. And I have one, it works good in Cali. Last year I was in Truk with it and was able to drop into holes that the Choptima couldn't follow me.
Choptima is very much a swiss army knife. There are so many ways to configure it. rEvo plus would be dual scrubber that you rotate through. Very good safety record. Negative is dealing with the most O2 cells of any rebreather out there. Choptima negative is the non-common O2 bottle size. That is a travel only issue. When you travel to most places that specialize in rebreather divers, they will have 3L steel bottles. Pretty much the standard rebreather bottle. Comptima will have you bringing your own AL13 O2 bottle.

Now for your plans for MOD2 level of diving for quite a while. I will call that a good plan.

No matter what, your diving is limited by the proper amount of bail out. In general for MOD 2, you will be bringing a pair of bail outs with you. Every single dive. So while a rebreather looks very compact, don't forget that there are bail outs that are not prominent in the marketing photos.

That's my rambling.

 

[BoltSnap]

No matter what, your diving is limited by the proper amount of bail out. In general for MOD 2, you will be bringing a pair of bail outs with you. Every single dive. So while a rebreather looks very compact, don't forget that there are bail outs that are not prominent in the marketing photos.

If one is diving to let's say 70 meters, will the CCR diver have less tanks and less bulk/weight than an oc BM diver even with the bailouts?

 

[Wibble]

I am considering the XCCR as my top choice but that BM unit is going to be a bear for travel. Not sure if you can easily convert the same unit between BM and CM for travel and local.

XCCR is a big box with a large radial scrubber for long durations. This means it uses a lot of Sofnolime, thus is expensive to run. Packing the scrubber also takes a while — lots of tappety tap, tappety tap, turn drop, tappety tap…

One of the CCR considerations has to be scrubber size especially if you’re not doing more "extreme” diving with umpteen hour runtimes.

As a Revo diver, one of the great benefits I get is the scrubber recycling. Typically, if the dive is 3 hours or less, only one of the two scrubbers is refilled with just 1.3kg/3lbs of Sofnolime. This then provides a full length dive without replacing all Sofnolime. Obviously if I’ve done more than 4h on the Revo, I’ll refill both.

For a week of deepish diving to 70m/230ft with 2h to 3h runtimes, I only refill one scrubber per day., e.g. 4 fills of 1.3kg =5.5kg All other units need their large scrubbers refilling unless the diver is prepared to push their scrubbers over a couple of days = lots of Sofnolime.

At $250 per 20kg/44lb keg in the USA — or much more in Truc/wherever — it’s definitely a consideration. In the UK Sofnolime is £95/$120 per keg.

Chestmount rebreathers have smaller scrubbers and tend to be smaller and lighter so make excellent travel rebreathers.