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Thread: Calculating NDL and multi-level dives by hand

 

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    zor
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    Calculating NDL and multi-level dives by hand

    I'm interested in learning how to calculate nitrogen absorbtion, no decompression limits and multi-level dives by hand. Where can I find the equations/tables of absorbtion rates of tissues/whatever this actualy takes? I've got a vague idea of the theory and I've taken integral calculus so I think I can handle the math, but google hasn't been any help on this one.

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    jbd
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    Quote Originally Posted by zor
    I'm interested in learning how to calculate nitrogen absorbtion, no decompression limits and multi-level dives by hand. Where can I find the equations/tables of absorbtion rates of tissues/whatever this actualy takes? I've got a vague idea of the theory and I've taken integral calculus so I think I can handle the math, but google hasn't been any help on this one.
    Buy Basic Decompression, Theory and Application by Bruce R. Wienke. You will find plenty of math with some overview of the various theories that have been around.

    You can look at www.bestpub.com to order.
    NAUI Instructor PSI Cylinder Inspector
    Buoyancy control specialist
    Buoyancy Control and Breathing Control are conjoined twins that cannot be seperated without both dying---Uncle Pug

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    rab
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    I don't remember exactly where I found it, but I downloaded a PDF of Bruce's Decompression Theory. It's 182 pages and full of all the math and tables that you could possibly want. I believe the link came from this board (and may have been posted by Bruce himself).

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    Get a Padi wheel it dose just what you want. And you can take it with on dives.
    Dive Safe
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    And only work on your gear if you are trained to do so and have the right tools.
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    visit http://www.lizardland.co.uk/DIYDeco.html

    Then get the Buhlmann tables. Buhlmann is not that hard.

    For VPM stuff, see

    http://www.decompression.org/maiken/...blications.htm
    "I think the only true expression of one's beliefs lies in action." Michael Crichton, Down Time

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    Definitely get a PADI wheel. You can easily teach it to yourself and do all of the calculations that you mentioned. It's portable and waterproof too.
    PADI OW, AOW, RESCUE, NITROX :scubadive

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    zor
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    Quote Originally Posted by Shoc369
    Definitely get a PADI wheel. You can easily teach it to yourself and do all of the calculations that you mentioned. It's portable and waterproof too.
    yeah, I want to know how its calculated, and I'm planning on getting a dive computer rather before a wheel and would like to have a better understanding of how they work. What I'm hoping to do here is program my TI-89 to do what the padi wheel does, but out of the water obviously. I might start out writing a web based version since I program mostly in perl though so I can figure the algorithms out, and because ti basic is a pain in the neck.

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    All of these can be located by searching the web...

    If you still have questions after reading all of this, you're going to become famous.

    Bruce R. Weinke:
    Modern Decompression Algorithms: Models, Comparisons, and Statistics
    Reduced Gradient Bubble Model in Depth
    Basic Decompression Theory and Application
    Basic Diving Physics and Application
    Technical Diving in Depth

    Johnny E. Brian, Jr.:
    Gas Exchange, Partial Pressure Gradients, and the Oxygen Window

    Erik C. Baker:
    Clearing up the Confusion About Deep Stops
    Understanding M-values
    Gone diving.

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    Padi now has their new eRDP, an electronic dive planner. I learned on the tables, not the wheel, but to my understanding multilevel dives are easy to make on the table, just calculate your SI as 0 minutes and calculate as you would a multiple dive using the RAT. The RDP is a NDL table, so you get both in one setup, you should have learned the basics of how to use it in OW, you can always go back to your instructor and learn again if you forgot. The programming however, I have no clue.

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    Quote Originally Posted by Justin699
    , but to my understanding multilevel dives are easy to make on the table, just calculate your SI as 0 minutes and calculate as you would a multiple dive using the RAT.
    On some dive profiles this will cause you to exceed NDL during the dive, and perhaps would cause you to surface while still having a decompression obligation per the DSAT/PADI model. While the pressure groups and the single level NDLs of the PADI wheel are the same as for the PADI RDP table, the wheel has additional reduced NDL limits for multilevel dives, and also restrictions on allowable combinations of multilevel depths.

    Even though this 0 SI method can cause you to violate the PADI/DSAT model a bit, it is still a reasonable way to do some rough planning. Just remember that a dive to the limits using this method are actually a bit beyond the limits of PADI/DSAT model.

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