So now I'm an SF2 instructor...

[kensuf]

I dove a KISS for a year and a half logging around 250 hours on the unit. I loved my KISS, and it was a great unit to get me started on diving CCR's, and I had a couple of opportunities to become a KISS instructor but there was one thing that kept troubling me. My KISS had zero flood tolerance and for the diving I was doing, it was possible I could be 4 or more hours away from the surface. Without the ability to recover a flooded loop, this could be a disaster and I decided I needed to look at other options.

Last fall James Draker from ScubaForce USA let me take an SF2 on a try dive. I told him one of my concerns with my KISS was the inability to recover from a flooded loop, and that my goal on the try dive was to put the SF2 to the test.

Five minutes into the try dive I took the DSV out of my mouth, turned it upside down, and completely flooded the unit. James had a horrified look on his face as I shook the loop hoses making sure every last bit of gas was out of the unit, mostly because he expected that like most sane people, I would try the flood test at the end of the dive. After de-watering the unit I stayed on the loop for an extra two hours, never once having to go to the surface or bailing out. The SF2 performed wonderfully and I ordered mine the very next day.

Since receiving my SF2, I've put it through it's paces in many different and challenging environments.

7 hour dives in Eagles Nest? Check.

350' dives in salt-water? Check.

12,000' cave penetrations in 15' of vis? Check.

Traveling to foreign countries? Check.

My SF2 has been flawless and I've enjoyed every minute of diving it. The more I dive it, the more I realize it's an incredibly robust, yet simple, machine. Care and maintenance are quick, assembly is straight forward, and with no over the chest counter-lungs, the unit is very clean and uncluttered.

Fast forward to last week.. James Draker ran an SF2 instructor institute for Carsten Huppertz from Florida Keys Dive Center (FlaKeys) and myself. Our student, Tracy, managed to put up with countless boom drills, shooting lift bags at turtles, and even a monsoon. At the end of the week, Tracy was a new SF2 diver and Carsten and I were new SF2 instructors.

I'm going to be helping with a CCR "Try Dive Weekend" on May 6th and 7th here in High Springs, FL. It'll be a two day event and an opportunity to learn about, play with, and try several units including the SF2, JJ, Fathom, and KISS Sidekick. If you're interested in rebreathers, but not really sure, please feel free to join us. Details are at the event page, Rebreather Workshop

 

[RainPilot]

Congrats Ken! Heard nothing but good things about those units.

 

[macado]

Nice report. I'll admit I'm intrigued by the SF2. It seems to be well engineered unit and it looks like it breaks down easy for travel. James did a breakdown for me at BTS and I have another local friend up here that dives one.

I've got about ~370 hours on my rEvo but starting to look at other units in the future, mainly for flood tolerance. How do you find the work of breathing?

 

[kensuf]

Nice report. I'll admit I'm intrigued by the SF2. It seems to be well engineered unit and it looks like it breaks down easy for travel. James did a breakdown for me at BTS and I have another local friend up here that dives one.

I've got about ~370 hours on my rEvo but starting to look at other units in the future, mainly for flood tolerance. How do you find the work of breathing?

Well, I came from a KISS so the restrictive work of breathing is quite a bit better than my old KISS.

In terms of hydrostatic WoB, one of the nicest things about the SF2 is the placement of the counter-lung bellows; the location keeps you in horizontal trim. Diving in this position the unit breathes as easy as if I was sitting on my couch in my living room. If I'm diving feet down, I will get a bit of chipmunk cheeks, but I never dive in that position anyway.

 

[JohnnyC]

Congrats! I recently ordered an SF2 through James. Can't wait to get it in the water.

 

[victorzamora]

If I'm diving feet down, I will get a bit of chipmunk cheeks, but I never dive in that position anyway.

Then how do you walk down the cave passages?

 

[macado]

Thanks. I'm doing a demo on one hopefully soon. Now the hard question on a public forum..Is there anything you don't like about the SF2?

 

[JohnnyC]

Thanks. I'm doing a demo on one hopefully soon. Now the hard question on a public forum..Is there anything you don't like about the SF2?

I don't have mine yet, so this is purely based on the research that drove me to swap my Meg for an SF2.

The only real "negative" I've heard about the SF2 is that due to the counterlung location, the WOB goes up if you're vertical in the water column. It seems to be the number one negative, and at first seems pretty glaring. However, I took a look at my diving, both OC and CCR, in the context of the perceived "issues" with the SF2. What I realized is that it's a complete non-starter.....I dive in trim. It's not hard. If you're in any way a skilled diver, it's the natural position you'll be in by default, so it's a moot point. "It breathes bad if you're not in trim..." Well, why the eff aren't you in trim?! You're a rebreather diver, not a warm water tourist who just got their OW ticket last week. Not an acceptable excuse.

I can totally see there being an issue if you're the type of diver who thinks the PADI Type R rebreather courses are a great idea. You see fun videos of them on youtube stepping on coral as they're head up in the water with an Explorer blinking away on their back and their bailout flopping around like a speared snapper. That's not how you dive the SF2 (or any rebreather for that matter), and the "negative" only pokes it's head up when you're diving in a manner that you should be well past by the time you're strapping an anesthesia machine to your back and get wet.

 

[victorzamora]

The only real "negative" I've heard about the SF2 is that due to the counterlung location, the WOB goes up if you're vertical in the water column. It seems to be the number one negative, and at first seems pretty glaring. However, I took a look at my diving, both OC and CCR, in the context of the perceived "issues" with the SF2. What I realized is that it's a complete non-starter.....I dive in trim. It's not hard. If you're in any way a skilled diver, it's the natural position you'll be in by default, so it's a moot point. "It breathes bad if you're not in trim..." Well, why the eff aren't you in trim?! You're a rebreather diver, not a warm water tourist who just got their OW ticket last week. Not an acceptable excuse..

Sometimes it's not possible in a cave...and if I'm diving a sidemount CCR it's so I can get in a cave. Of course there are ways to mitigate that, and there aren't really better options out there yet, but it's not as easy as just "stay flat all the time" for some folks.

My main concern with it is the counterlung size. I have a 7.5ish Liter lung capacity, and my understanding is the SF2 is optimistically rated at 4.2L

 

[kensuf]

Thanks. I'm doing a demo on one hopefully soon. Now the hard question on a public forum..Is there anything you don't like about the SF2?

I'm happy to be share my honest opinion.

Hydrostatic work of breathing sucks if you're feet down. I try not to dive that way, so it's a moot point for me. I do not find head down to be a problem.

I wish there was a second digital canbus port for a backup controller. It does come with a Fischer, so you can use a petrel EXT (or NERD or Narked @ 90 HUD), but that's only a monitor.

It took me a long long time to get over the carbon fiber. I raced bikes for five or six seasons and saw more than my share of broken frames and wheels. However, the SF2 tube is substantially thicker than most bike frame designs (weight is a major issue in cycling).

There's only one scrubber design -- I cannot get a bigger scrubber. The design is a 6# axial scrubber. On the other hand, I have done 7 hour dives with the scrubber and know people that have done longer dives without any problems and I'm not planning on doing anything much beyond what I'm already doing.

A stock unit comes with a few things that I removed right off the bat. Specifically, I don't like the idea of shut-offs going into the solenoid or O2 MAV. Those were pulled off the minute I received my unit.