Thoughts on dive soft liberty?

[tbone1004]

@Josh the diver I think you'll get a lot of the same advice from the same people.

My opinion is take Mod1 before you buy a unit with very few exceptions. You are not qualified to judge a unit in the water until you have at least dealt with the course. Pick the instructor you want to use first, then pick a unit that is close ish to what you think you want. I.e. if you want to dive a Meg, taking a Fathom course from @kensuf is good enough because the Fathom is basically a mCCR Meg, but you're getting instruction from Ken. After that course, you can then dive a Meg and see if it makes sense to you.
MOST rebreathers are generically similar so if you take a course on a unit with OTS counterlungs, it should dive pretty similar to all of the other OTS lung units out there and then you make your decision based on what your buddies dive, if there is a specific differentiating factor to a unit that brings it ahead of the others, deals on a unit *i.e. I would never have chose to dive an old Meg, but one was given to me, so that obviously changed my course*.

Now. The Liberty is a really neat unit and despite having a lot more "stuff" inside of it is actually no more complicated at a fundamental level than anything with a DiveCAN on it. What does that mean? Essentially all eCCR's currently sold are using CANbus technology to deal with the electronics. Shearwater is the big boy, but they were nowhere near the first. Poseidon has been using their own CANbus for a really long time, as have APD, and several others. This is the same technology used in your car where there are individual modules that have two-way communication for data validation. Using DiveCAN terms because Shearwater has done a better job of explaining how theirs works. In the simplest units, there is a a central computer *SOLO with DiveCAN* that is the hub for all data. It receives data from the oxygen sensors, sends signal to the solenoid, sends data to the handset and receives changes from the handset. Most units are only using that function, however it can also have ambient pressure sensors, high pressure sensors, CO2 sensors, myriad of other things that it can process. Most of the units also have an OBOE board which is a separate canbus system that runs the monitor *HUD, NERD, whatever is spitting out O2 data that is not the controller*. The SF2 for some reason still uses analog communication for this, but I suspect it's because it wouldn't fit in the head. What is important to note here is that on most units the SOLO and OBOE are both reading from the same sensors. O2ptima has one non-shared sensors and the Revo is weird.
The Liberty has chose to use redundant SOLO equivalents instead of a SOLO/OBOE concept. Each SOLO has independent O2 sensors, He sensor, computer brain, monitor/controller, solenoid, and pressure sensors. There is a data bridge between the two sides and the first one that is turned on becomes the master, the other the slave. The nice part of this is that if one side fails, you still have a fully functional rebreather and everything is modular so you should never have to send the head back for service unless you bugger up the threads or contacts *which is operator error, the unit can't do that to itself*, everything else is swappable modules.

So is it too complicated? I don't know, it's quite complicated, but I think it's a lot less bad than some of the other units out there in terms of what it can do and how it works. Is it better than an mCCR? It depends. I don't like CMF's and much prefer needle valves, but I also much prefer to just have a solenoid and call it a day because the solenoid can actually support life if it is functioning where the CMF's can only preserve it *passive injection, so it buys you time, but if you're working it will still fall*. I do have a mCCR with leaky valve which will get swapped to a needle eventually so it's not that I have hard and fast rules, it's more personal preference.

So what exactly about the Liberty has you wanting it? What other units are you looking at and why is the Liberty leading the pack?

 

[Josh the diver]

@Josh the diver I think you'll get a lot of the same advice from the same people.

My opinion is take Mod1 before you buy a unit with very few exceptions. You are not qualified to judge a unit in the water until you have at least dealt with the course. Pick the instructor you want to use first, then pick a unit that is close ish to what you think you want. I.e. if you want to dive a Meg, taking a Fathom course from @kensuf is good enough because the Fathom is basically a mCCR Meg, but you're getting instruction from Ken. After that course, you can then dive a Meg and see if it makes sense to you.
MOST rebreathers are generically similar so if you take a course on a unit with OTS counterlungs, it should dive pretty similar to all of the other OTS lung units out there and then you make your decision based on what your buddies dive, if there is a specific differentiating factor to a unit that brings it ahead of the others, deals on a unit *i.e. I would never have chose to dive an old Meg, but one was given to me, so that obviously changed my course*.

Now. The Liberty is a really neat unit and despite having a lot more "stuff" inside of it is actually no more complicated at a fundamental level than anything with a DiveCAN on it. What does that mean? Essentially all eCCR's currently sold are using CANbus technology to deal with the electronics. Shearwater is the big boy, but they were nowhere near the first. Poseidon has been using their own CANbus for a really long time, as have APD, and several others. This is the same technology used in your car where there are individual modules that have two-way communication for data validation. Using DiveCAN terms because Shearwater has done a better job of explaining how theirs works. In the simplest units, there is a a central computer *SOLO with DiveCAN* that is the hub for all data. It receives data from the oxygen sensors, sends signal to the solenoid, sends data to the handset and receives changes from the handset. Most units are only using that function, however it can also have ambient pressure sensors, high pressure sensors, CO2 sensors, myriad of other things that it can process. Most of the units also have an OBOE board which is a separate canbus system that runs the monitor *HUD, NERD, whatever is spitting out O2 data that is not the controller*. The SF2 for some reason still uses analog communication for this, but I suspect it's because it wouldn't fit in the head. What is important to note here is that on most units the SOLO and OBOE are both reading from the same sensors. O2ptima has one non-shared sensors and the Revo is weird.
The Liberty has chose to use redundant SOLO equivalents instead of a SOLO/OBOE concept. Each SOLO has independent O2 sensors, He sensor, computer brain, monitor/controller, solenoid, and pressure sensors. There is a data bridge between the two sides and the first one that is turned on becomes the master, the other the slave. The nice part of this is that if one side fails, you still have a fully functional rebreather and everything is modular so you should never have to send the head back for service unless you bugger up the threads or contacts *which is operator error, the unit can't do that to itself*, everything else is swappable modules.

So is it too complicated? I don't know, it's quite complicated, but I think it's a lot less bad than some of the other units out there in terms of what it can do and how it works. Is it better than an mCCR? It depends. I don't like CMF's and much prefer needle valves, but I also much prefer to just have a solenoid and call it a day because the solenoid can actually support life if it is functioning where the CMF's can only preserve it *passive injection, so it buys you time, but if you're working it will still fall*. I do have a mCCR with leaky valve which will get swapped to a needle eventually so it's not that I have hard and fast rules, it's more personal preference.

So what exactly about the Liberty has you wanting it? What other units are you looking at and why is the Liberty leading the pack?

I like the redundancy of the unit and the options of conversion kits to sidemount or the light versions. I have also looked at optima or kiss sense my local instructor teaches these units.

 

[tbone1004]

I like the redundancy of the unit and the options of conversion kits to sidemount or the light versions. I have also looked at optima or kiss sense my local instructor teaches these units.

Both O2ptima and KISS have conversion kits for some of their units, as does SF2. O2ptima can go to chest mount, and the sidekick can be backmounted or Spirit turned into a sidewinder, though I will say that converting these things can be more trouble than it's worth and as cheap as you can buy some of them, it's a lot easier and not much more expensive to just buy a dedicated unit. I.e. the Liberty Sidemount conversion kit is almost $5k, which is the price of a used O2ptima and not much less than a used Liberty...

 

[ChuckP]

The bright shiny advertising they do doesn't hurt either - by that I mean all the informational videos they have on their website - most other companies have virtually zero.

Just trying to read between the lines and see if the bright shiny stuff is a cover or real.

 

[Josh the diver]

Both O2ptima and KISS have conversion kits for some of their units, as does SF2. O2ptima can go to chest mount, and the sidekick can be backmounted or Spirit turned into a sidewinder, though I will say that converting these things can be more trouble than it's worth and as cheap as you can buy some of them, it's a lot easier and not much more expensive to just buy a dedicated unit. I.e. the Liberty Sidemount conversion kit is almost $5k, which is the price of a used O2ptima and not much less than a used Liberty...

the conversion kits was not a big deal to me, I just thought it was nice.

 

[tbone1004]

also, local instruction should not be that critical in your decision making as it does not necessarily equate to the best instruction. If that instructor is not actively diving the types of dives that you want to do at at least that level, preferably a higher level, then you hsould seek out alternate instructors...

 

[stuartv]

@Josh the diver I think you'll get a lot of the same advice from the same people.

My opinion is take Mod1 before you buy a unit with very few exceptions. You are not qualified to judge a unit in the water until you have at least dealt with the course.

Based on my experience with just my one unit, I am not convinced that a lot of people would be qualified to judge even after finishing MOD1. It definitely took me a fair bit longer than that before I felt like my "judgment" of my unit had stabilized.

If doing a whole MOD1 course on a unit still isn't really enough to REALLY form a solid opinion, then what is the point? Why not just do the due diligence and pick a unit that makes sense on paper. Shop well for a good, clean used unit at a fair price. Do your MOD1 on that and rack up some time on it. THEN you can actually make a reasonably well-informed decision about whether that unit is right for you long term. And, if it's not, you have enough experience to have a reasonable idea of what your requirements should be for your next unit. Plus, you can sell the one you bought for (probably) around what you paid for it (again, presuming you bought used at a fair price). And you didn't waste money renting a unit for a week, either.

That seems like a better way to end up with the best unit for you while also being the most financially conservative, at the same time.

I know guys that have bought 3 clean, used Prism2s in the last year. Prices were anywhere from $2500 - 3200. I have bought 2 used rEvos in the last 2 years. The most I paid was $4750.

Also, I think I have learned a LOT more about CCRs and rEvos, in particular, by buying used. Just sayin'...

 

[stuartv]

Regarding eCCRs and redundancy, I can only really speak from my (relatively newbie) experience with my rEvos.

It seems to me that saying the Liberty is redundant - and implying that other units are not - is not entirely fair.

My rEvo does not have redundancy for the automation aspect of an eCCR. But, it is still almost fully redundant. If the primary controller dies, then I do have a backup controller. It is the combination of my NERD2 monitor, O2 sensors for the NERD2 that are completely independent from the ones that connect to the primary controller, the manual adds for O2 and Dil, and my brain.

My primary controller can die. 3 sensors can die. My ADV and solenoid can both die. All at the same time. And I still have complete control of my breathing loop. It's just no longer fully automatic. And that is why (to my newbie perspective) the Liberty seems unnecessarily complex.

The existence, popularity, and solid safety record of mCCRs shows us proof that electronic control of a CCR is a convenience, not a requirement. So, redundant electronic control is not only not a requirement but, MAYBE, a liability.

As someone brought up earlier, with fully redundant controls, can you start a dive knowing that one set of controls is dead? (e.g. in the middle of the ocean, one system is dead, and your choices are dive it like that or miss diving for the rest of your liveaboard trip) What are the safety implications of diving a Liberty where one system is dead from the start? Does Liberty training include diving it with one system dead, or is the training that when one system dies you turn the dive (implying that the training is that you don't start a dive with one dead system)?

 

[stuartv]

MOST rebreathers are generically similar so if you take a course on a unit with OTS counterlungs, it should dive pretty similar to all of the other OTS lung units out there

That seems valid. So, what are the different types that one should really consider?

Generic OTS (including chest mount CL?) includes which units? Prism2. O2ptima. Meg/Tiburon.

Generic BMCL includes? X? JJ (not sure at all how the CLs are configured on JJ)? Prism2? O2ptima?

Chest mount units? Dive Rite CM. Titan?

Side mount units? Various KISS. SF2 (in SM config)

Some seem like they'd be in more than on category because there are options on how you can configure them.

Then you have ones that are somewhat unique. Like:

SF2 - counterlungs inside the canister on your back. Can be BM or SM.

rEvo - unique in many ways


Does this seem like a valid breakdown?

 

[broncobowsher]

Based on my experience with just my one unit, I am not convinced that a lot of people would be qualified to judge even after finishing MOD1. It definitely took me a fair bit longer than that before I felt like my "judgment" of my unit had stabilized.

If doing a whole MOD1 course on a unit still isn't really enough to REALLY form a solid opinion, then what is the point? Why not just do the due diligence and pick a unit that makes sense on paper. Shop well for a good, clean used unit at a fair price. Do your MOD1 on that and rack up some time on it. THEN you can actually make a reasonably well-informed decision about whether that unit is right for you long term. And, if it's not, you have enough experience to have a reasonable idea of what your requirements should be for your next unit. Plus, you can sell the one you bought for (probably) around what you paid for it (again, presuming you bought used at a fair price). And you didn't waste money renting a unit for a week, either.

That seems like a better way to end up with the best unit for you while also being the most financially conservative, at the same time.

I know guys that have bought 3 clean, used Prism2s in the last year. Prices were anywhere from $2500 - 3200. I have bought 2 used rEvos in the last 2 years. The most I paid was $4750.

Also, I think I have learned a LOT more about CCRs and rEvos, in particular, by buying used. Just sayin'...

That goes with my comment about how much can go wrong but it is still safe to be on the loop. The only things that will really get you off the loop is a failure of the loop (flood, CO2 breakthrough, broken loop hose). And the only way around that is another rebreather, the bail out breather.

Pretty much any failure in any rebreather will result in the electronics not controlling it anymore and you fly it manually. And flying a rebreather manually isn't as bad as it sounds. That is what training is for. Not nearly as stressful as it sounds.