Choosing my first rebreather SF2 vs JJ

[GF99/99]

I was doing some research on the XRC since i do some point plan on trying the JJ. Is the 6 hour rating on XRC CE rated? Or is the calculation based on scrubber size?

And where did you find the SF2 CE rating at 135min? The manual says no more then 3 hours/180min

Yes it is a CE rating

Check pg. 13 below is snip shot of it. They sneakily word it "as part of the certification" and then go on to state the CE test parameters, like I said SF does not like to advertise it but technically they need to inform there customers. Also it is a mission to get the actual CE test results from SF.

Trust me I would know my the guy on the cover of the SF2 manual is a friend and also use to be my next door neighbor.

As I mentioned above much earlier the biggest problem and the No Go for me on the SF2 is the scrubber. The OP is specifically asking about deep wreck diving. This is basically what the JJ was designed for. Proper deep exploration diving. Yeah sorry the SF2 is not built for that. I like my life too much to be running a CE rated 135min scrubber way over. Ill stick to the JJ 4kg radial XRC scrubber (almost twice the size of the SF2 scrubber) on a 6-8hr deep deco dive.

I think scrubber ratings is one of the most overlooked things people do not take into account when buy a unit. And also during dive planning. What if you have an issue and over stay your bottom time and rack up alot more deco, our you need to do in water recompression, or your in a cave and get lost and now your 6hr dive turns into an 8hr dive, how confident are you in your scrubber???. Usually people are always looking at WOB, CL location, cool fancy features like He sensors, pressure transmitters, etc. But don't forget your life if most dependent on your scrubber. And sorry a 135min CE rating is pretty sad. It is also something that most SF2 instructor do not disclose or like to talk about.

Direct from the SF2 manual pg. 13. Also SF does not like to share the CE test results, you will see that JJ will share them no issue.

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[Alex Ouroboros]

Thats pretty standard for all rebreathers. Usually all of them you can get about 10% more in the scrubber then advertised.

Also lets be real most exploration diving now is going way beyond 100m or penetration length in overhead is getting crazy now, especially with the B/O rebreathers becoming popular.

More and more people are diving deeper, further (overhead) and alot longer nowadays. Might want to have a look at what units all the current guys and gals doing crazy deep, crazy long dives are using.




As I said befor yeah if you want to over dive a 135min rated scrubber go for it and I am sure within reason it is safe, but... That is a calculated risk you have to take. I am not saying that you can not as we all know the CE test is unrealistic no human can actually maintain a the test parameters but it is still a standardized test that shows the true flow and scrubber effectiveness. And sorry the SF2 did very very poor.

Personally putting 322min on a 135min rated scrubber is not worth the risk to me. I like my life to much and want to continue diving and in the grand scheme of things ill pay the extra to change my scrubber out. To put things in perspective 322min/135min means your over diving your rating 2.39 times.

My JJ XRC scrubber rated for 6hr so if I did what your doing that would be like diving it for 14.31hr. yeah sorry not worth the risk.

A few of the Brits that are doing the long deep dives are using XCCR B/M with Flex2 B/O (both IQ sub) or Liberty B/M & S/M,
JJ and rEvo are also favourites, the rEvo gaining a lot of pace recently due to the new uk distributor being pro active in getting the machines out there and having strong links with the manufacturer. I think you still see mainly XCCR and JJ though as they are very good units for UK diving.

 

[rjack321]

Rule of thumb is 1 pound per hour. But, that varies GREATLY based on many factors, including diver workload, water temperature, and other things.

Maybe in warm to moderate (8C+) water. But this would be super iffy in Lake Superior (3C).

 

[stuartv]

Maybe in warm to moderate (8C+) water. But this would be super iffy in Lake Superior (3C).

Exactly why my post said:

Rule of thumb is 1 pound per hour. But, that varies GREATLY based on many factors, including diver workload, water temperature, and other things.

 

[rjack321]

Exactly why my post said:

I know the OP is in SE Asia so maybe didnt have a good barometer for when cold is serious

 

[rjack321]

Exactly why my post said:

I know the OP is in SE Asia so maybe didnt have a good barometer for when cold is serious

 

[Herje8990]

Maybe in warm to moderate (8C+) water. But this would be super iffy in Lake Superior (3C).

I primarily dive in Okinawa. It was 28-30C at 6M lol coldest it got was 23C

 

[Martin Strandbygaard]

I find the unit really hard to breathe to the point where my chest felt like it was burning and buoyancy all over the place. However, articles online informed me that its normal and will be better after getting more experience.

I think what you have been reading online sounds reasonable.

I have about 150 hours on an X-CCR. I have no personal experience with the SF2, but it's widely used. InDepth magazine just published an article about long term diving experiences on it, in June (SF2 – The Good, the Bad, the Beautiful).

"Hard to breath" - was counter lungs front or back mounted? and were you trim in the water.

All rebreathers involve compromises. It's hard to know which you will end up prioritizing, until you get some experience with a unit. And you priorities will also change once you get some hours on it.

For sure buoyancy is like learning to ride a bike all over again.

When getting into rebreather diving,local community, servicability, and a good instructor were most important to me, and I chose the model they were diving.

I'm moving towards a sidemount rebreather, for lower travel weight and better buoyancy - and in doing so, I'm compromising on other qualities of my X-CCR, including fantastic work of breathing and build quality.

I've written about my motivations here Why I Chose a Sidemount Rebreather?

 

[Henry_LKW]

"Hard to breath" - was counter lungs front or back mounted? and were you trim in the water.

apparently the instructor told me I was below minimum loop volume hence the burning / hard to breathe feeling. yup I was in trim and at times 5 to 10 degree off trim

 

[Henry_LKW]

I know the OP is in SE Asia so maybe didnt have a good barometer for when cold is serious

anything below 25 degrees celsius is cold for me and my group HAHAHA