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Nitrox course. What's the point?

Discussion in 'New Divers and Those Considering Diving' started by Dody, Jan 9, 2021.

  1. MichaelMc

    MichaelMc Working toward Cenotes ScubaBoard Supporter

    # of Dives: 100 - 199
    Location: Berkeley, CA
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    1,259
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    Simplicity is good. I think you'll find a computer useful though. But you might have to venture off plan to see the benefit.
     
    mac64 likes this.
  2. ToneNQ

    ToneNQ ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Australia
    269
    343
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    The hope is not blind, hence when the computer is truly, absolutely essential, people have redundancy. People ensure the battery is charged, the firmware is updated, tissue logs are not inadvertently cleared. In the map example, coverage failure doesn't leave you lost, it leaves you exactly where you're standing. If you had the forethought to think about coverage you could've downloaded offline maps..

    Risk is a factor of consequence and likelihood, no single method insulates you from both. Computers greatly reduce the likelihood and consequence by tracking your dive with second by second data samples. Analogue instruments are only as good as the frequency they are monitored. Accuracy of the dive profile is less, therefore to control the likelihood of DCS you must increase the conservatism of the dive plan. If the vis is great and the wreck is good and the gas is going well, I can add 5min of bottom time, or spend a bit longer in the bottom decks, without any increase in risk. With analogue gear that is not wise, I really must stick to the plan and hope everything holds for the next dive.

    To be clear, I'm not suggesting any reason for you to change. I will suggest your reasons listed to not change are inaccurate but that has no bearing on your current methods.
     
    Pressurehead and boulderjohn like this.
  3. Angelo Farina

    Angelo Farina Marine Scientist

    # of Dives: 1,000 - 2,499
    Location: Parma, ITALY
    1,653
    2,493
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    You said that your reset the bezel of your watch before ascending, This means that the dive time to be inserted in the table is evaluated at that moment... Instead I reset the bezel only when I have reached the first deco stop (6m, usually) and I read the time to be entered on the table. So I include the ascent time in the dive time. How do you include it, if you reset the bezel before ascending?
    See your post. Perhaps I did not understand exactly what you did mean... But to me, it seems that you are following the procedure described in the US NAVY manual, where the dive time ends at bottom, before the ascent.
     
  4. Storker

    Storker ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 100 - 199
    Location: close to a Hell which occasionally freezes over
    16,767
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    I read that as adding the time from the bottom to his first deco stop to his total bottom time, unlike most tables which stops counting bottom time as soon as you leave the bottom and depend on a minimum ascent rate to avoid excess ongassing.

    To me, that looks like a decent way to avoid messing up by taking too long to ascend (ongassing on the way), and it would introduce some conservatism into the schedule. It still doesn't avoid messing up by failing to properly note max depth, though.
     
  5. tursiops

    tursiops Marine Scientist and Master Instructor ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: U.S. East Coast
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    You know, someday they will invent a fork, a thing to help you eat. I'll bet it will be a whole lot safer and easier than spearing everything with your knife.
     
    Degenerate, ToneNQ and DiveClimbRide like this.
  6. doctormike

    doctormike ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: New York City
    6,778
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    Perhaps I didn't explain clearly.

    The only way to for a MOD alert to use "depth" would be if it actually MEASURED your depth. Which it doesn't. The only way you can measure depth directly would be to use something like a marked line and use that for your calculations during the dive.

    Your computer doesn't measure depth. It measures ambient pressure, which it then converts to a depth using that constant so that you can have it displayed on your screen, so you can know how deep you are. But that derived number is not what is used to determine your current PPO2, which is what you actually care about for ox tox purposes. PPO2=ATA x FiO2. No feet or meters in that formula.

    So, theoretically, yes, the computer could work with a variable called depth that it would calculate from ambient pressure by taking into account the salinity constant. But after that, to see if you were over your PPO2 alert value, it would have to adjust the result by taking into account that same constant again to calculate the MOD with your formula ("putting it in and taking it out").
     
  7. Angelo Farina

    Angelo Farina Marine Scientist

    # of Dives: 1,000 - 2,499
    Location: Parma, ITALY
    1,653
    2,493
    113
    Probably it is as you say, let's see if @mac64 provides a clarification.
    My point is: if later you have to add the ascent time to the bottom time, what's the purpose of resetting the bezel at depth, before ascending, causing the need of remembering two numbers and to make the addition? I prefer not resetting the bezel at depth, and watching the total dive time, which already includes the ascent time, when I arrive at 6m (and I am not narched anymore)...
    The procedure described by @mac64 still appears to me unnecessary complex, hence less safe.
     
  8. Angelo Farina

    Angelo Farina Marine Scientist

    # of Dives: 1,000 - 2,499
    Location: Parma, ITALY
    1,653
    2,493
    113
    Max depth is shown by the secondary needle of the depth gauge. This has never been a problem for old-style divers using tables with an analog watch and a mechanical depth gauge...
    $_59.JPG
     
  9. mac64

    mac64 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 5,000 - ∞
    Location: Ireland
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    I reset the bezel to time the assent, I’m not using navy tables, I’m using IDeco Pro. Bottom time is from leaving the surface till you start the assent. I posted an example. I have all possible run times on a slate, usually 3, if conditions are poor I’ll leave early. If conditions are very good I’ll stay longer.
     
  10. mac64

    mac64 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 5,000 - ∞
    Location: Ireland
    749
    478
    63
    That’s a ridiculous analogy. I could use a spoon. If I was to follow your thinking I would have to sit with my mouth open while a machine feeds me. I just don’t want to go that helpless
     
    Graeme Fraser likes this.

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