JJ Cmoptima and the liberty

[Glen the explorer]

Hi all,
New to this forum/platform in the keys we have the availability of these 3 units. I’m mostly aiming for a unit for deep dives wreck and longer bottom time and maybe but maybe later on caves. Not planing to travel often with the unit.
Which one would you go with and WHY?!
Dan Dawson wasn’t really helpful lol! Both unit are good the JJ and liberty!
I need your help!
Cheers !

 

[tbone1004]

If you go with the JJ or the Liberty then for boat diving I personally think you need to go with the Heavy variants of them. With the JJ this is similar to the GUE configuration, and the Liberty has the "heavy" variant when you purchase. This consolidates everything on your back and lets you be no more of a nuisance to the crew than anyone in doubles. You still have all of your deco bottles hanging, but your deep bailout is all on your back. This is a big and heavy configuration, similar to double LP121's, but it is NICE for boat diving.
The O2ptima CM or Choptima is nice to clip onto the front of your existing doubles but is definitely a bit more clunky IMO than the backmount rigs. Great for what it is, basically adding a CCR to whatever your standard rig is, but it's a bit too chest heavy for my personal liking, and I have no problem running around with a heavy configuration backmount CCR, even in the seas we experience in the mid-Atlantic/Carolinas which are a bit sporty for getting back on the boat.

 

[Glen the explorer]

If you go with the JJ or the Liberty then for boat diving I personally think you need to go with the Heavy variants of them. With the JJ this is similar to the GUE configuration, and the Liberty has the "heavy" variant when you purchase. This consolidates everything on your back and lets you be no more of a nuisance to the crew than anyone in doubles. You still have all of your deco bottles hanging, but your deep bailout is all on your back. This is a big and heavy configuration, similar to double LP121's, but it is NICE for boat diving.
The O2ptima CM or Choptima is nice to clip onto the front of your existing doubles but is definitely a bit more clunky IMO than the backmount rigs. Great for what it is, basically adding a CCR to whatever your standard rig is, but it's a bit too chest heavy for my personal liking, and I have no problem running around with a heavy configuration backmount CCR, even in the seas we experience in the mid-Atlantic/Carolinas which are a bit sporty for getting back on the boat.

If you’ll have to decide on a unit which one will you go for and why?

 

[tbone1004]

If you’ll have to decide on a unit which one will you go for and why?

Of those 3, the Liberty Heavy, not even a question.
JJ has very limited US support outside of GUE, and it's not a modular head design so if stuff goes wrong it's irritating to deal with. Both Dive Rite and Liberty are modular designs so individual components can be replaced easily but also have legit Florida based HQ. Dive Rite obviously being based there, but Liberty has a legit operation in Cave Country as well, so just on that the JJ is written off in my book.

After that it's just about the rig profile that you want. The Liberty Heavy is a beast, but if you think about it you have your deep bailout/diluent and your inflation bottle fully integrated into the rack which is not that much worse than a big set of doubles. Grab whatever deco bottles you need and you're off to the races. The Choptima is just not a design that I personally enjoy diving, I like my chest to be free and clear. It is a clear choice if you were traveling, but since you say it isn't a consideration then the Liberty is IMO a better form factor. My Meg is configured similarly to the Liberty Heavy so I'm probably a bit biased since several of us were diving that configuration before they started selling it as a factory configuration, but if you're strong enough to move it around it is a super clean configuration.

For either of the units I would strongly recommend making the pilgrimage up to Cave Country and get trained up there though.

 

[rsfinn57]

For travel is it easy to convert the heavy liberty to the light system

 

[tbone1004]

For travel is it easy to convert the heavy liberty to the light system

true, but travel concerns with that breather are a lot more than the Choptima so if you're traveling regularly, especially to places that are not heavily invested in CCR's the Choptima is infinitely easier to deal with

 

[Timmy23]

true, but travel concerns with that breather are a lot more than the Choptima so if you're traveling regularly, especially to places that are not heavily invested in CCR's the Choptima is infinitely easier to deal with

Aren’t you concerned on the liberty computer since they used their own software and no shearwater for the controller?
That’ll be also one of my concern since they use proprietary software

 

[tbone1004]

Aren’t you concerned on the liberty computer since they used their own software and no shearwater for the controller?
That’ll be also one of my concern since they use proprietary software

I've been using Divesoft computers for years and I think they actually have some incredibly safety improvements vs. the Shearwater *which is also proprietary*. You can manually vote out individual cells which is huge and they had haptics going a long way back. I haven't had any issues in many hours on multiple units. You can't do much with the software anyway, so as long as it has a deco algorithm that works for you *Divesoft and Shearwater both use effectively the same algorithm* and the solenoid works *which it does* then there isn't much that you can really worry about.

 

[Jona Silverstein]

While I recommend diving what the people around you are diving, I do not recommend locking yourself into the bubble just because those are the only units TAUGHT in your area. You'll find almost every unit everywhere if you look hard enough.

My question is what other units would you want to look at other than the 3 you asked about. And while several have noted the advantages of back-mounted bailout, theres other options to take a look at aswell. (Cough cough, a standard config fathom with 30s)

I do not like the HEAVY config of any rig unless the dives being done warrant it. Deep wreck diving is ambiguous so hone in a little bit on the style of diving you want out of the rig. For some a deep dive is 110ft. Others is 200ft. and then theres the DEEP crowd that like the 300+ range. I dont feel that a heavy config is beneficial to me unless I am going to be carry more than 2 80s for bailout. only then do I feel that moving gas to my back makes sense. I like being able to hand my stuff off to others, and I also like being able to get up from the floor by myself.


And as for the comment about not being able to get shearwater... Shearwater is just as proprietary as everyone else. Its all decompression calculation and how you want to see the data. Lets not forget some of us used to fly a rebreather with a bottom timer, a voltmeter, and a set of tables...

 

[DiveLikeAMuppet]

Get whatever other people around you dive.

JJ is lovely in stock configuration, perfectly fine to dive from a boat and by far “stock backmount” are the most common setups, at least in Europe. We do have lifts on boats. Most popular units tend to be AP, JJ (stock), rEvo and XCCR. I’m yet to see a Liberty on a boat (they are all over the internet and dive shows though …)

The difference between a JJ and Liberty is that JJ doesn’t try to be clever - it either works or it doesn’t. Whether one approach is better than the other is probably a philosophical question, I can imagine that Liberty recovering from a failure is a nice feature few hours inside a cave. On the other hand, JJ never needed a screensaver to save battery on computers (this has changed but it does show a design approach).