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Computer + Plan or 2 Computers for Deco Diving

Discussion in 'Technical Diving Specialties' started by Kohanbash, Nov 26, 2019.

  1. Kohanbash

    Kohanbash Solo Diver

    # of Dives: 200 - 499
    Location: PA, USA
    99
    22
    8
    Hi all
    For deco dives, do you
    1. Have one deco/tech computer then a gauge/timer and prewritten dive plan?
    2. Use two deco/tech computers

    If option 1:
    Do you use the prewritten plan or the computer, as your primary means of following a decompression profile?
    Do you have the written plan on a wrist slate, or wet notes?

    If option 2:
    How much do you follow the computer for a plan vs a predefined dive plan?

    Thanks!
     
    markmud likes this.
  2. doctormike

    doctormike ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: New York City
    6,353
    6,010
    113
    For CCR, two computers - one controller, one NERD. For any planned deco, I have the bailout plan written on a wrist slate (white duct tape and fine sharpie). Yes, I recognize that in case of total electronics failure and an OC ascent, I wouldn't be decompressing as efficiently as I would with constant PO2 and bailing out could put you into deco, but I don't take a slate for NDL dives. The total ascent time would be pretty short and I would certainly pad it if it happened near the end of the dive.

    When doing OC I had one computer, a bottom timer and the wrist slate.

    I use the computer to run the dive, since it's giving me credit for time spent above a square profile, which is almost always the case. Wrist slate is for a computer failure. Since my slate doesn't know what I actually did, it's not going to be as accurate in running my ascent.
     
  3. NothingClever

    NothingClever Barracuda

    # of Dives: 200 - 499
    Location: Red Sea and Atlantic Ocean
    303
    330
    63
    This.
     
  4. JohnnyC

    JohnnyC PADI Pro

    # of Dives: 1,000 - 2,499
    Location: United States
    3,341
    3,673
    113
    2 computers. At this point in the game, with the reliability of modern computers, and the benefits of having accurate data, there's no reason not to just go with two.

    In the past, when bottom timers were cheap, and computers were expensive, it made lots of sense to run bottom timers and cut tables. Now, you can get used Shearwaters for the same price as a bottom timer. Technical diving isn't a poor man's game, if you can't afford $400 for a used Shearwater, you realistically can't afford to be a technical diver.

    That doesn't mean all of that's useless, and I carry backup tables in my wetnotes on every dive in case I screwed the pooch and screwed up my gases or something, I can always use depth and time to safely ascend. I just don't feel that it's an intelligent use of money to spend almost $600 for a Freedom, find an old Uwatec that may or may not be on its last legs, or $200 for the ScubaPro one, when a couple bucks more gets me into an actual computer from any number of manufacturers.
     
    Bigbella, drainaps, Kmart921 and 7 others like this.
  5. lermontov

    lermontov Manta Ray

    # of Dives: 500 - 999
    Location: christchurch
    795
    354
    63
    OC-
    two computers one set at GF 40/85 the other set at 90/90 (90/90 is for emergency exit protocol)
    no cut tables
    wrist slate with just as little info as possible ( theory: if you lose 2 computers your in extremis keep it simple)
    wrist slate info based on deco planner information pre dive planning :
    A) turn time -
    B) turn pressure -
    C) calculated maximum deco time based on half available deco gas carried

    decision based on whatever comes first
     
  6. NothingClever

    NothingClever Barracuda

    # of Dives: 200 - 499
    Location: Red Sea and Atlantic Ocean
    303
    330
    63
    While I value your perspective and conviction, I think this is a narrow position to take.

    Riding high-performance motorcycles on a track, a passion of mine that pre-dates diving, isn’t a poor man’s game, either.

    When I need to make choices between Italian race control switches, Australian carbon fiber wheels and weighing aftermarket fuel mapping versus race cams and a new Shearwater, a second Shearwater can wait.
     
    100days-a-year likes this.
  7. JohnnyC

    JohnnyC PADI Pro

    # of Dives: 1,000 - 2,499
    Location: United States
    3,341
    3,673
    113
    A second Shearwater can be had for $400. A NitekQ is $200. That's either $200 more than you'd be spending on your backup device, or the same price you'd be spending on your backup device.

    "I can't afford a redundant piece of life support equipment because $200 will keep me from buying $8000 worth of new wheels" is an interesting argument. Stuff like that is why the Rouse's decided to dive air instead of trimix, and we all know where that got them.

    We're not talking about spending 12 grand on a rebreather when you just wanna piddle along a reef, we're talking about an insignificant amount of money for a significantly greater return. And we're not talking an insignificant amount of risk either.

    I dunno man, you gotta pay to play safely. When safety takes a backseat for insignificant reasons, bad things tend to happen. It's not that you can't do those dives with a bottom timer and tables as backup, there's just no good reason to.
     
    BlueTrin, markmud, ChuckP and 4 others like this.
  8. KenGordon

    KenGordon Rebreather Pilot

    2,605
    1,365
    113
    It sounds like your bike bits are upgrades, the second computer isn’t so much an upgrade as a different approach. I expect your upgrades make a bit off a difference from day one, the extra computer you hope to never need although it simplifies prep.
     
    BlueTrin and markmud like this.
  9. lermontov

    lermontov Manta Ray

    # of Dives: 500 - 999
    Location: christchurch
    795
    354
    63
    i dont think thats a good comparison the difference between a slate and a shearwater is more like road tyres versus slicks
     
  10. jvogt

    jvogt Solo Diver

    # of Dives: 200 - 499
    Location: Lakewood, CO USA
    266
    186
    43
    Two PDCs. Slate has:

    1) Target Depth
    2) Min Gas
    3) Max TTS

    Typically dive shallower than target and ascend at Max TTS.
     

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