• Welcome to ScubaBoard


  1. Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

    Benefits of registering include

    • Ability to post and comment on topics and discussions.
    • A Free photo gallery to share your dive photos with the world.
    • You can make this box go away

    Joining is quick and easy. Login or Register now by clicking on the button

Stack timer question (rebreather use)

Discussion in 'Shearwater Research' started by broncobowsher, Jan 20, 2019.

  1. broncobowsher

    broncobowsher Solo Diver

    862
    381
    63
    On the stack timer I see 2 options. When the computer is on and when diving.

    The "computer on" option isn't good, I tend to have the computer up and running without being on the loop. Checking that I have all the settings right, etc. Post dive I keep it on and go back to review the dive, or check surface interval, etc.

    The "while diving" option isn't good either. Doesn't count the pre-dive. Dive doesn't start until descent and I have spent too 10-15 minutes bobbing around on the surface waiting on others before starting the dive. Staying on the loop and racking up scrubber time.

    Am I missing something here? Is it really just counting the dive time? I have no intention of trying to push the scrubber to the limits, I just don't want mess up and put a lot of time on the scrubber that isn't being counted, nor do I want the clock to be ticking just because the computer is on.

    Maybe I am confused or missed something, feel free to correct me.
     
  2. Shearwater

    Shearwater Dive Equipment Manufacturer

    252
    424
    63
    Hi. @broncobowsher . You have described the stack timer behavior correctly. The stack timer has no direct connection to the scrubber itself and is unable to automatically activate when somebody starts breathing through it.
     
    northernone likes this.
  3. broncobowsher

    broncobowsher Solo Diver

    862
    381
    63
    Any way to get it to start counting stack time when the 0.19 setpoint is switched off? Since the 0.19 is pretty much a standby setting.
     
  4. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
    15,392
    6,693
    113
    how accurate are you trying to get the stack timer and to what benefit? Sounds like you should just leave it on dive mode and add 15mins/dive
     
  5. Shearwater

    Shearwater Dive Equipment Manufacturer

    252
    424
    63
    @broncobowsher, we'll take your suggestion under consideration, but we cannot promise to implement it.
    You can also edit the stack timer total time to be 15 less minutes. For instance, you could reduce the default time of 3 hrs to be 2hrs and 45 mins.
     
    tbone1004 likes this.
  6. broncobowsher

    broncobowsher Solo Diver

    862
    381
    63
    Why would I want to cheat a computer. If a simple change can improve the accuracy, why not ask for it?

    I'm already cutting the stack timer short by 30 minutes. But I would like to keep more accurate data on the scrubber. How much time I actually have used it since dive time doesn't count all of it.

    Shearwater, thanks for looking into it.
     
  7. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
    15,392
    6,693
    113
    so what's your suggestion to @Shearwater on how to start it?

    also no guarantee of .19 being turned off since some still fly eCCR's manually with it left at .19. Best option would be a manual start option, but I think their suggestion on just cutting the stack hours short is better. Hours are also pretty subjective too as you know, so you're only ever estimating it anyway. If I were you, I'd just use the "dive" time and manually track your prebreathe time no different than you would adjust the stack time based on temperature, exertion, etc.
     
  8. broncobowsher

    broncobowsher Solo Diver

    862
    381
    63
    Tell you what, just turn your stack timer off. It is clear that you don't use it. You may run it, but not use it.
    Some of us look to improve things that we find problems with.
     
  9. doctormike

    doctormike ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: New York City
    5,844
    4,960
    113
    I use the 0.19 setting primarily when I'm downloading dive logs, to avoid running the solenoid. It's rarely on for long enough to make a significant difference in stack time if I was using the "computer on" setting. Other than that, it's either off or on, when I start my pre-jump checklist. So while I see what you are saying, the accuracy of just estimating how many minutes of pre-breath and surface time you usually use and taking that off of your estimated scrubber duration seems to be a reasonable solution.

    As you probably know, scrubber times are very loose estimates, and are typically extremely conservative from the manufacturers. It makes sense to just pick a conservative number and not push the scrubber more than that. The additional accuracy you would get by using "computer on but setpoint above 0.19" is tiny compared to the true variation in scrubber duration related to, for example, water temperature, work of breathing, etc... Most people don't try to calculate those things to get more mileage out of their scrubbers, because it's clear that it's just a very rough and conservative estimate.

    I would go with the Shearwater suggestion.
     
    rjack321 and tbone1004 like this.
  10. doctormike

    doctormike ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: New York City
    5,844
    4,960
    113
    And some of us listen to experienced divers who are trying to help us without being snarky.
     
    rjack321 and RainPilot like this.

Share This Page