Choosing my first rebreather SF2 vs JJ

[happy-diver]

dude people go off the loop on those things to tackle planes other than horizontal as the breathing is too difficult

 

[Wibble]

The SF2 has bellows for the counterlung at the bottom of the unit. This means when you're vertical, there is more pressure on the bellows/lung which means you have a much greater work of breathing. It's fine when horizontal.

Comparison between the two units:

• The JJ is pretty much the "standard" rebreather unit, well regarded, thousands sold, based upon the "standard" backmount style from the AP Inspiration which inspired many other rebreathers (Meg, X-box, Prism, etc...).
  The JJ is very much the no-brainer unit to choose for starting your rebreather career
• The SF2 is an unusual unit that is more like a sidemount unit put onto backmount. It's rarely seen and is very much an esoteric machine. You'd very much be on your own trying to maintain it and configure it for diving. Unless you've a load of SF2 unit divers around you, it is not the unit to choose.

There are many other rebreathers around which will all work as your first unit. Have a look on the local (technical) dive boats for the most common rebreathers.

One requirement you may have is for a lightweight rebreather for travelling. See this thread for info on different rebreather unit weights. The chestmount rebreathers are almost half the weight of a backmount unit.

The most important thing for your move from open circuit to a rebreather is that a rebreather is a long-term commitment. You must spend a lot of time diving it to get your skills up to standard and get the most from the unit. I'm talking two years minimum and 200 hours.


Will add my preference: Revo. That's a great unit, reliable and easy to maintain. The Micro version is lighter weight, the Mini version fits most people. I really like my Revo.

 

[GF99/99]

Hi all! I'm here looking for advice on which rebreather to get! Living in Singapore, there is not much CCR diver presence and the one of the only means to get certified would be to cross the border to Malaysia (about 4 hrs) to get any form of technical diving training. The dive shop I'm approaching (and where I did my Padi Tec 50) offer to sell a lightly used SF2 (but manufactured many years back) inclusive of the course at about 5500 USD. During my try ccr with the unit (my first experience in a ccr), 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.

However, I also have been reading online where there are multiple users recommending the JJ CCR over the SF2 due to the easier WOB and reliability which the dive shop teaches on as well!

Would like to seek some opinions if I should spend the money on a new JJ CCR or go for the used SF2 use the money I saved for CCR consumables and future courses down the line?

My end goal for diving with a CCR would be for deep wrecks and cave diving!​

The SF2 has bellows for the counterlung at the bottom of the unit. This means when you're vertical, there is more pressure on the bellows/lung which means you have a much greater work of breathing. It's fine when horizontal.

Comparison between the two units:

• The JJ is pretty much the "standard" rebreather unit, well regarded, thousands sold, based upon the "standard" backmount style from the AP Inspiration which inspired many other rebreathers (Meg, X-box, Prism, etc...).
  The JJ is very much the no-brainer unit to choose for starting your rebreather career
• The SF2 is an unusual unit that is more like a sidemount unit put onto backmount. It's rarely seen and is very much an esoteric machine. You'd very much be on your own trying to maintain it and configure it for diving. Unless you've a load of SF2 unit divers around you, it is not the unit to choose.

There are many other rebreathers around which will all work as your first unit. Have a look on the local (technical) dive boats for the most common rebreathers.

One requirement you may have is for a lightweight rebreather for travelling. See this thread for info on different rebreather unit weights. The chestmount rebreathers are almost half the weight of a backmount unit.

The most important thing for your move from open circuit to a rebreather is that a rebreather is a long-term commitment. You must spend a lot of time diving it to get your skills up to standard and get the most from the unit. I'm talking two years minimum and 200 hours.

Pretty spot on!

Also some other things to consider are:

• SF2 resale value = horrible (there is a reason for this, might give you some insight on the unit) but I guess this could be a good thing also if you in the market to buy one second hand.
• JJ resale value = very high. (But like the SF2 on the reverse this makes it difficult to find a used ones for a good price)
• You mentioned you want to dive deep and caves. This will mean long run times. Keep in mind the SF2's CE scrubber rating is only 135min (yeah yeah we know this is conservative but still it is the CE rating) CE rating for JJ axial is 3hr, radial is 4hr, and XRC is 6hr. As you get more experience you can upgrade your scrubber.
• Also the JJ is much easier to configure for "expedition" style diving. Try strapping 4 onboard tanks and a canister light to an SF2 cleanly and easily.
• The JJ has a stand personally for deep diving with 4 bailouts I find with 4 B/O the tanks sit much nicer stand clipped.
• The JJ comes with standard LPI connections for the O2 and dil MAV's for easy plug ins of offboard gas.
• You mention your in Singapore. So another consideration is availability of high quality Mod 1, 2, and 3 instructors near you. I think you will find trying to find this near SG for the SF2 is quit difficult. I think Miko Passi in Koh Tao is the only one I can think of off the top of my head (and sorry nothing against him but the SF2 is not his primary unit) For the JJ you have quite a few include Will Goodman in Gili T who has more hours on a JJ than anyone I know and also a former world record 290+ meter dive on a JJ.

Personally for me the sf2 scrubber rating is such a no go. In warm tropical water using DPV's I am happy to over run the CE scrubber rating but only within reason. It is pretty hard to do a deep dive or solid cave dive in under 4hr. Are you really going to overrun the SF2's scrubber almost twice what the CE rating is??? Yeah yeah im sure there are people doing it but does that really mean its ok . How much is your life worth. Remember a Co2 hit at depth or in a overhead environment would be very hard to recover from.

Also on a side note. I too really enjoy deep diving and cave diving and at the level of diving I am at the cost of a JJ or any other unit is is not a factor at all that I take into account. The unit I choose and trust my life with is the JJ. Even If I had unlimited money I would still pick the JJ. The only reason why I own other units if for specialized diving like cave (small where the JJ does not fit)

Just had my JJ at -200m 2 weeks ago and it ran flawlessly. These units are amazing.

 

[Henry_LKW]

There are many other rebreathers around which will all work as your first unit. Have a look on the local (technical) dive boats for the most common rebreathers.

rebreathers are kinda uncommon where I am from! There is only 2 dive shops here locally that supports rebreather servicing which is the JJ and Choptima and even so, there is only a hand full of JJ divers and slightly more for the Choptima

Will add my preference: Revo. That's a great unit, reliable and easy to maintain. The Micro version is lighter weight, the Mini version fits most people. I really like my Revo.

This was once in my list of choice but got bumped out due to no immediate support and is about a 4 hr flight and 2 hrs drive

 

[Henry_LKW]

Pretty spot on!

Also some other things to consider are:

• SF2 resale value = horrible (there is a reason for this, might give you some insight on the unit) but I guess this could be a good thing also if you in the market to buy one second hand.
• JJ resale value = very high. (But like the SF2 on the reverse this makes it difficult to find a used ones for a good price)
• You mentioned you want to dive deep and caves. This will mean long run times. Keep in mind the SF2's CE scrubber rating is only 135min (yeah yeah we know this is conservative but still it is the CE rating) CE rating for JJ axial is 3hr, radial is 4hr, and XRC is 6hr. As you get more experience you can upgrade your scrubber.
• Also the JJ is much easier to configure for "expedition" style diving. Try strapping 4 onboard tanks and a canister light to an SF2 cleanly and easily.
• The JJ has a stand personally for deep diving with 4 bailouts I find with 4 B/O the tanks sit much nicer stand clipped.
• The JJ comes with standard LPI connections for the O2 and dil MAV's for easy plug ins of offboard gas.
• You mention your in Singapore. So another consideration is availability of high quality Mod 1, 2, and 3 instructors near you. I think you will find trying to find this near SG for the SF2 is quit difficult. I think Miko Passi in Koh Tao is the only one I can think of off the top of my head (and sorry nothing against him but the SF2 is not his primary unit) For the JJ you have quite a few include Will Goodman in Gili T who has more hours on a JJ than anyone I know and also a former world record 290+ meter dive on a JJ.

Personally for me the sf2 scrubber rating is such a no go. In warm tropical water using DPV's I am happy to over run the CE scrubber rating but only within reason. It is pretty hard to do a deep dive or solid cave dive in under 4hr. Are you really going to overrun the SF2's scrubber almost twice what the CE rating is??? Yeah yeah im sure there are people doing it but does that really mean its ok . How much is your life worth. Remember a Co2 hit at depth or in a overhead environment would be very hard to recover from.

Also on a side note. I too really enjoy deep diving and cave diving and at the level of diving I am at the cost of a JJ or any other unit is is not a factor at all that I take into account. The unit I choose and trust my life with is the JJ. Even If I had unlimited money I would still pick the JJ. The only reason why I own other units if for specialized diving like cave (small where the JJ does not fit)

Just had my JJ at -200m 2 weeks ago and it ran flawlessly. These units are amazing.
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Thanks for such a detailed explanation! appreciate it alot!

I probably could only afford to own 1 CCR and I guess JJ CCR is a all-rounded one!

Is it a huge hassle to travel with JJ by air? I read alot online in regards to how some divers would dismantle the JJ to hand carry on the plane etc

 

[Henry_LKW]

SF2 resale value = horrible (there is a reason for this, might give you some insight on the unit) but I guess this could be a good thing also if you in the market to buy one second hand.

That could explain why the dive shop is quoting at such competitive price

 

[GF99/99]

Will add my preference: Revo. That's a great unit, reliable and easy to maintain. The Micro version is lighter weight, the Mini version fits most people. I really like my Revo.

This was once in my list of choice but got bumped out due to no immediate support and is about a 4 hr flight and 2 hrs drive

Not to contradict my post above but I will say that the Revo is a very very solid unit as well actually Marc Crane in Amed, Bali probably has more hours on a Revo than anyone in the world and is a fantastic instructor and can provide you all the support you need. Not to mention most stuff gets shipped to SG first and then sent from there to Bali so SG is a great location to get parts etc for them.

 

[Henry_LKW]

Not to contradict my post above but I will say that the Revo is a very very solid unit as well actually Marc Crane in Amed, Bali probably has more hours on a Revo than anyone in the world and is a fantastic instructor and can provide you all the support you need. Not to mention most stuff gets shipped to SG first and then sent from there to Bali so SG is a great location to get parts etc for them.

is there a need to return the unit to Mares/REVO for servicing? similiar to the JJ?

 

[GF99/99]

Thanks for such a detailed explanation! appreciate it alot!

I probably could only afford to own 1 CCR and I guess JJ CCR is a all-rounded one!

Is it a huge hassle to travel with JJ by air? I read alot online in regards to how some divers would dismantle the JJ to hand carry on the plane etc

Obviously compared to a chest unit or sidewinder it is a little bit more of a pain in the butt, however its not more difficult to travel with than any other back mounted unit.

I have a Pelican 1637 that the unit fits in perfect (just need to remove the handle) and then a just pack clothing around it. I do put the head in my carry on (I dont want this banging around). I also put all my regs in my carry on as well to save on weight.

But if you traveling with a rebreather just expect to have excess luggage. Actually to me the hassle is all the extra crap like, dry suit, super heavy Jet Fins, undergarments, spare parts, lights, reels, etc. etc.

That could explain why the dive shop is quoting at such competitive price

probably because you in Asia, all the import tax

 

[DiveLikeAMuppet]

is there a need to return the unit to Mares/REVO for servicing? similiar to the JJ?

One really useful way to understand different units and philosophy of the manufacturer is to read their user manuals (read AP Inspo too).