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View Poll Results: What Deco Algorithm Do You Use?

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  • Bubble Model

    3 3.03%
  • Varying Permeability Model

    10 10.10%
  • Gradient Factors – Even – Like 30/70 or 20/80

    49 49.49%
  • Gradient Factors – Favor Deep Stops – Like 20/70

    4 4.04%
  • Gradient Factors – Favor Shallow Stops – Like 40/80

    33 33.33%
  • Ratio Deco

    9 9.09%
  • Tables – Like Navy

    2 2.02%
  • Other - please explain

    4 4.04%
Multiple Choice Poll.
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  1. #21

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    Quote Originally Posted by Nitrogenius View Post
    GF hi sets your relative conservatism, but be weary that one influences the other so GF X/70 vs GF Y/70 never does represent the same level of conservatism of your overall deco.. The only thing it says is that your LEADING Compartment will have an MValue of equal or lesser than 70% of its allowed highest value according to Buhlmann original values..
    Bit of a correction:
    The GF high sets the conservatism on surfacing.
    As opposed to low which sets the conservatism on the start of offgassing.

    Quote Originally Posted by Jax View Post
    Negative.
    There simply are people that move their gradient factor choice the same percentage from the absolute.
    The only way to keep the same percentage from the absolute (the absolute being straight Buhlmann) is to have GFs of 10/10 or 20/20 or 80/80.
    Again, the GF low is a percentage of straight Buhlmann when your very first tissues start to offgass (others may still be ongassing).
    The GF high is your percentage of straight Buhlmann on hitting the surface.

    So if you were diving straight Buhlmann (100/100) you aren't diving 200 of anything. It's just that your M-Value is 100% the entire way up. When you adjust those numbers, or just leave them at 30/70 at some point you will be at 47% then at 63% of Bulmann's model of offgassing, then, as you ascend you'll get closer and closer to 70%. When you reach it at your last stop... your computer will tell you you are clear to exit the water.

    So there is no rational value or point it trying to balance the two number to equal 100. Because it isn't 100 OF anything. They're two independently working points to create a "slope" of ascent.


  2. #22

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    Quote Originally Posted by Jax View Post
    Negative.

    There simply are people that move their gradient factor choice the same percentage from the absolute.
    Well just note that this approach has no merit whatsoever..


  3. #23

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    Quote Originally Posted by oya View Post
    Bit of a correction:
    The GF high sets the conservatism on surfacing.
    As opposed to low which sets the conservatism on the start of offgassing.

    bit of a counter correction
    yes the GF hi sets the conservatism on surfacing to some extend.. But only in relation to the lead tissue/compartment..
    Depending on what you had been doing before, your remaining tissues might be significantly more saturated with GF X/F versus GF Y/F with F being kept constant (hence I called it F for fixed)
    That is actually what the whole NEDU study discussion is about..
    So if you think that with moving your Deco strategy from lets us an example 10/80 to 40/80 that you are in fact maintaining the same level of conservatism at surfacing because you kept the GF hi constant, then you are very wrong with that assumption.
    In fact your middle speed compartments will likely get a higher saturation level.. and hence the overall stress to the body might be higher and hence the decompression in fact be more aggressive and thus riskier..
    In fact when raising your lo GF (from some point that works for you) you will want to reduce your GF to achieve the same "overall decompression/supersaturation stress over all tissues" when surfacing
    In fact this is an area where staying costant in the sum of GF lo and hi might have some value.. I d still suggest to go via analyzing the overall decompression time and keep that constant..


    The lo GF sure also stands somewhat for a conservatism on the start of offgasing in the most supersaturated tissue, but at the values used there and for the purpose they have been introduced I find the terminology conservatism a deceiving choice of words and not really representative..


    Quote Originally Posted by oya View Post
    They're two independently working points to create a "slope" of ascent.


    Right but one has to keep in mind that this slope is jumping between the leading compartments all over the place especially when altering the GF lo..
    While for the first stop the relevant compartment and its M value will always be the same, the compartment "setting" the slope in comparison to the GF lo value is at a constant change..
    It is not one slope we are dealing with but 16, when using GF with ZHL-16 or 8 when using ZHL-8 (if anybody does that)
    So it is a bit comparable with jumping form 2 dimensional thinking into 3 dimensional..
    This is what makes fiddling with GFs less easy as it appears at first sight and the main reason why GF X/F is not providing the same conservatism as GF Z/F


    BTW finally watched Simons video..
    Great summary on RBWs debate (where I had my share of "fun" dealing with ill perceptions of a certain bubble model programmer) back in late 2013 (at least before a lot of it had been censored).
    You have to admire Simon that even with the heated debate his presentation is relatively unbiased and simply sticking to the facts established and being careful on explaining what it in fact does support and what not..
    Cudos to this guy!
    Unfortunately there was no bit of new info since then of which I had hoped for (like further real life reports of divers shifting the GFs from deeper stops to shallower stops)
    BTW Simon states he is diving some 50/70, if I remember well he was coming from something like 25/85 or alike..
    Note the reduction of the high GF along with it from the professional MD here.. And believe me he is not doing that to introduce a higher conservatism, but to keep it stable..


    If I wasn't able to relay it properly, reach out to him I am sure he will respond and he will support what I stated here in regards to conservatism.. We ve been there many times in that +100 pages discussion back in 2013..


  4. #24
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    Quote Originally Posted by Nitrogenius View Post
    Well just note that this approach has no merit whatsoever..
    I'll not argue anyone's choices.


    Quote Originally Posted by Nitrogenius View Post
    In fact when raising your lo GF (from some point that works for you) you will want to reduce your GF to achieve the same "overall decompression/supersaturation stress over all tissues" when surfacing
    I am not sure where the hang-on to this "sum to 100" came from - that was never expressed to me.

    It is simply that some people raise their Lo GF a certain percentage, and reduce their Hi GF the same percentage. That it adds to anything is coincidence.

    Great minds discuss ideas; Average minds discuss events; Small minds discuss people. ~ Eleanor Roosevelt

    "If a small thing has the power to make you angry, does that not indicate something about your size?" ~Sydney J. Harris

  5. #25

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    Quote Originally Posted by Jax View Post
    I'll not argue anyone's choices.
    You don't have to argue anything there.. it was meant as an fyi to you and anybody else reading..
    If you are using GF macke sure you understand it and make your own conclusion on how to implement it.
    When you do that then you will understand yourself the lack of merit to keep GFs sum at 100...


  6. #26

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    Quote Originally Posted by Nitrogenius View Post
    bit of a counter correction...
    Awesome stuff. Thanks!


  7. #27
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    Quote Originally Posted by Nitrogenius View Post
    You don't have to argue anything there.. it was meant as an fyi to you and anybody else reading..
    If you are using GF macke sure you understand it and make your own conclusion on how to implement it.
    When you do that then you will understand yourself the lack of merit to keep GFs sum at 100...
    Good discussing, thanks!

    Great minds discuss ideas; Average minds discuss events; Small minds discuss people. ~ Eleanor Roosevelt

    "If a small thing has the power to make you angry, does that not indicate something about your size?" ~Sydney J. Harris

  8. #28

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    Does anyone here use different gradient factor settings depending on the planned depth and dive duration? i.e., which theoretical tissue compartments are controlling the ascent?


  9. #29
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    Quote Originally Posted by Troglodyver View Post
    Does anyone here use different gradient factor settings depending on the planned depth and dive duration? i.e., which theoretical tissue compartments are controlling the ascent?
    I do. The deeper/longer I go the more conservative the deco. More shallow time, less deep stops.


  10. #30

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    Quote Originally Posted by PfcAJ View Post
    I do. The deeper/longer I go the more conservative the deco. More shallow time, less deep stops.
    Explain the science or at least the logic on this practice. And define deep and long a little more.

    Two specific dives might help, one from each camp.

    I'm curious about this theory.

    Thanks!
    Bob



 

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