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SF2 or REvo rebreathers

Discussion in 'Rebreather Diving' started by JonnyQuest, Sep 29, 2017.

  1. NAND

    NAND Angel Fish

    # of Dives: 200 - 499
    Location: Germany
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    Hey JonnyQ,

    concerning your reasons, all 4 can be served by almost any CCR. Concerning point 4, gas cost must on CCR be mentioned with scrubber cost in one breath. My experience is that with increasing He costs it does in fact pay off, depending where you dive. Some remote locations will demand you to carry lime when flying in- this can add up to quite some charges for freight costs.

    I chose to prefer active scrubber monitoring with self-packed scrubbers to safely utilize most material. (I dive rEvo with RMS) However, it really depends where you dive. I believe in most parts of US you may get lime for the cost of a softdrink- may therefore not be the huge advantage.

    Concerning Point 1), both SF2 and rEvo are fully redundant. One often mentioned topic is that the shearwater controllers (used on both) do not offer any audible alarm feature. Its a hot topic sometimes- task loaded divers neglet their displays and miss warnings. The NERD may help a little- my opinion on this is that the fundamental rule of CCR diving is to know your PO2 at any point in time- with alarm or not does not matter.

    Points 2) and 3) apply to both- SF2 and rEvo.

    Point 4) was one of my critical issues as well, so far I am happy traveller with my unit, either checkin or carryon.

    Point 5) is not easy to answer. The method of diving depends on your needs and skillset. JohnnyC said it already. For Photography however, a CCR allows you very close contact to marine life- other than making noise and bubbles- perhaps that could be the main argument.

    Point 6)- Keep in mind the cost for training. My recommendation would be to do one or two 'discover rebreather' try dives before fixing your choice. CCRs can not be modified so much- your trim depends on the unit and the diver. (Skill, Bodymass) When casually testing and comparing you may even find out not to like CCR diving at all- if you like it then trying is better than guessing.

    Point 7) was my argument not to chose the se7en nor to continue on the Evo. Both SF2 and rEvo can be full hCCR- meaning you can either do a fully manual approach or use the eCCR for convinience. I normally dive manually but having the shearwater controller serving as a backup well below my target PO2. Taking videos/photos even the tiny amount of boyancy change during O2 injection pisses me off- Perhaps (in accordance to my GF) I am just a control-freak who wants to be self-reliant...

    Flood-recovery is often mentioned- not a point for me. This may depend on the diver- no unit however craps out on tiny amounts of water. When losing the loop you may have obviously other problems at the same time that will force you on bailout anyway.

    All this said, be aware- you will learn diving from a new beginning on. Switching to CCR makes you an OWD with terrible trim and skillset :wink: Its however worth all the trouble!!
     
  2. stuartv

    stuartv Seeking the Light

    # of Dives: 200 - 499
    Location: Manassas, VA
    8,173
    3,805
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    They have (or support) dual, redundant controllers?
     
  3. jason black

    jason black Angel Fish

    # of Dives: 100 - 199
    Location: Miami
    14
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    I personally like the SF2. Owned many units. Like the fact it is so clean and streamlined..... if you are into photography this would be a big benefit.... no clutter like other units. Very dependable, and solid support.
     
  4. joshk

    joshk Barracuda

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    Redundancy in monitoring loop PPO2.
     
  5. stuartv

    stuartv Seeking the Light

    # of Dives: 200 - 499
    Location: Manassas, VA
    8,173
    3,805
    113
    Doesn't every CCR offer that? The phrase used was "fully redundant". To me, that phrase would mean redundant controllers, so if one controller crapped out, you could switch to another controller, rather than having to fall back to flying manually.
     
  6. joshk

    joshk Barracuda

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    Suggest you use the phrase “redundant controllers” then. What unit do you dive? Does it have two controllers/solenoids?
     
  7. stuartv

    stuartv Seeking the Light

    # of Dives: 200 - 499
    Location: Manassas, VA
    8,173
    3,805
    113
    I have only tried the O2ptima. I'm about to start training on a rEvo. At this point. I'm just trying to learn what I can.

    I had read that the Liberty CCR actually does include dual, redundant controllers.

    CCR Liberty - fault tolerant rebreather

    That seems to qualify as "fully redundant". The SF2 and rEvo seem to qualify as "mostly redundant".

    But, maybe my lack of knowledge on the subject is leading me to an erroneous conclusion?
     
  8. The Chairman

    The Chairman Chairman of the Board

    # of Dives: I just don't log dives
    Location: Cave Country!
    56,264
    23,983
    113
    I want to learn this one as well

    It does, but only one solenoid. However, if you consider the diver a 'controller', then yes. :D The main Shearwater is the controller and monitor. Should it fail, the CAN Bus takes over both jobs, though you won't see the status of the cells. Add a PDC to the Fischer cable and now you have triple backup. However, should the CAN Bus fail, then your main Shearwater can't control it, but the diver can. I haven't been told if the primary Shearwater would still be displaying cell info. Ergo, I have another Shearwater on the Fischer just to be sure. Perhaps @Capt Tom McCarthy can weigh in on this.
     
  9. joshk

    joshk Barracuda

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    I hadn't remembered that the SOLO bus takes over in the event of a controller failure.
     
  10. stuartv

    stuartv Seeking the Light

    # of Dives: 200 - 499
    Location: Manassas, VA
    8,173
    3,805
    113
    What does the CANbus do with your set point if the handset controller croaks? Including what does it do when you ascend?
     

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