How about the SF2 Rebreather?

[Jeongmin Ha]

How does SF2 Rebreather compare to other Rebreather?
Though I'm not a Rebreather diver, I wonder about CCR.
I do not know which model is good or bad, and I do not know which model to choose.

please , reply me

 

[Danseur]

It is a good unit and the one I dive.

#1 Limitation is it is trim sensitive. If you are in a bad position, the WOB gets not so comfortable.

#1 Benefit is that it is extremely reliable and Russian Truck simple. Light weight as well!

I'd strongly suggest doing some try dives with this unit and others that you would consider.

 

[tstormdiver]

I primarily dive the Hollis Prism2. I have done a try dive on the SF2 & have to admit, I was rather underwhelmed. It took me a good 5 minutes to learn how to breathe on the unit (I'll admit, the Hollis is nearly effortless) & when I inverted (head down), I could not draw any breath, what so ever. As Danseur suggests, do some try dives on any units that interest you.

 

[taimen]

For someone who has no prior rebreather experience try dives are not that helpful when choosing unit.
There is too much basics to learn before you are able to appreciate the differences between the units.
Pick one that is common and well supported in your area and start diving.
Having recently switched to a rb I want to echo this advice. Very soon after training your priorities will be completely different from what you thought before actually diving a rebreather.

 

[rjack321]

Usually there are 2 to 4 units that are common in your areas and the owners are doing the dives you want to be doing. Find one of those model CCRs used, get some local training and go diving. You only really learn what you like and dislike after many hours in the water. By finding a used unit, if it turns not to your likely you can sell it for close to the purchase price. Then, while more CCR experience and knowledge find something that you love diving.

 

[Danseur]

Eh, you can tell a lot by try dives. Do you like front mounted counterlungs? Are they in the way? Do you find the way they breathe desirable? Not sure, here, dive the Back Mounted Counterlung unit over here... Additionally, in this regard, the SF2, Flex, Sidekick, Liberty, and Proteus also are in their own category, with sidemount an option or primary config. They also differ primarily in where the CL are located in relationship to your lungs which is the #1 factor in how they breathe.

In a pool, I tried a bunch in a row before I bought one. The Titan (defunct?) and Pathfinder (discontinued) were my favorite units to breathe, swim, and just mess around with... in 10' of water.

Units equipped with front mounted counterlungs are the easiest and most forgiving units to learn on. I went a different route as I was a sidemount cave diver looking to do sidemount caves on a rebreather. The Flex was too long for my 5'8" self (v2 shorter), and the Proteus was still new and I wanted a 2nd hand machine to stall my possible divorce over the bill on a new unit. Although I looked long and hard at it, Sidekicks use a slightly different philosophy and have yet to be adapted well to a backmount config.

Watch buddies tear down and clean their unit as well as build them. YouTube works if you need it.

The SF2 is a VERY flexible and robust unit, suitable for many varied missions. It's not the best for every type of diving, but it can do most all of it. Easy to pack scrubber, easy clean, easy assemble/disassemble, Shearwater electronics.

Try Dive it. Try Dive whatever your friends dive to see why they like or hate it. Make sure you can get sensors locally!

To be honest, my SF2 will likely not be my main rebreather after 75 meters or so. At that point it would be a bail-out-breather and a front mounted counterlung bulletproof unit like a Meg would take over as primary. How deep do you dive now on O/C? How far do you want to go?

What instructors do you have near you? What do they teach/dive, and do they have multiple units/certifications under their belt?

 

[RainPilot]

It would help if you define what you plan to use the unit for. Every unit has its own positive and negative aspects, many due to design choices made to allow the unit to excel in a particular area.

The SF2 is primarily a cave rebreather and especially side mount, tight cave. Other units are more suitable for open water, others are designed for very long dives, some for depth etc etc.

 

[Danseur]

Usually there are 2 to 4 units that are common in your areas and the owners are doing the dives you want to be doing. Find one of those model CCRs used, get some local training and go diving. You only really learn what you like and dislike after many hours in the water. By finding a used unit, if it turns not to your likely you can sell it for close to the purchase price. Then, while more CCR experience and knowledge find something that you love diving.

Good advice.

 

[JohnnyC]

What type of diving do you want to do? That will dictate some choices.

The SF2 is a fantastic unit. It’s dead simple, trims easily, easy to build, and has several very nice features. The WOB issues are significantly overstated. I can breathe on it in any orientation. Head up and head down (totally vertical) are less enjoyable than in trim, but I haven’t had any issues to where I’d even consider going off the loop.

That being said, every unit has advantages and disadvantages. Some are better suited than others for certain environments. Some allow more than one configuration. Some are really nice units in open water, but are wholly unsuited to a cave or a wreck.

It’s all a trade off and there is no perfect unit.

 

[kensuf]

Like EVERY rebreather, there are pros and cons to the SF2.

Pros:
Nothing dewaters better, period
Dead nuts simple to build and tear down
Clean unit to dive (no chest mounted clutter)
"Warm" -- one of the warmest units I've ever breathed.

Cons:
Hydrostatic WOB is less than ideal in certain orientatins (the only position I couldn't breathe in was literally horizontal but upside down with my feet tilted up)
Fixed scrubber size (the 5.5# scrubber is more than adequate for the majority of divers and dives though)

BTW, it's not just "a sidemount cave" rebreather. I mostly dive mine in backmount config and have had it in the ocean multiple times for deep wall diving, and it'll probably be the rig I take down to the islands when I go in Feb.