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Thread: "Long" bottom times below 100m

  1. #61
    Supporting Member Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36's Avatar
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    Re: "Long" bottom times below 100m

    Quote Originally Posted by PSotis  View Original Post
    Don, thanks.

    But WTF is wrong with people on these boards just looking for a reason to piss in everyone's cheerios? It's like a contest to see who can be the biggest AS*****. Maybe he thinks he knows more about diving than everyone. In my experience, it's rarely the case with these sorts of people.

    I don't care if people disagree and debate, but what is with all of this nasty bullshit? Clearly these people got beat up on the schoolyard too much when they were kids and it's pretty clear why...unfortunately, it did not turn them into better people.
    I actually do have a theory on this exact matter. It is much like the addiction to being sexually dominate or dominated, whichever applies. The individual is a very powerful business person with a lot of clout in his everyday life, but craves the exact opposite when not in public. Or he is a complete nothing in his day to day existence and then wants to dominate another in private.

    I think that most of these types of tossers are of the "complete nothing" in their daily lives and then want to try and impose there dominance from behind a keyboard. Not many still believe in the old school ways of backing up our mouths with action when called out.

    Of course, like with all my posts, I could be mistaken. Ah hell, who am I kidding, ya'all know that my word is gospel.
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  2. #62
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    Re: "Long" bottom times below 100m

    Quote Originally Posted by PSotis  View Original Post
    Hello Cathal,

    If I understand you correctly you are wondering if computer manufacturers that offer profiles in deeper diving are "tweeking" them? If so, i think you might be missing my point which is understandable.

    My point is not that they are making changes. My point is that you can get a bubble model and use its approach successfully to about 100 meters. But the deeper you get to 100 meters the less accurate it will be. And when you go beyond 100 meters you are really stretching it.

    Decompression modeling is compounding and dynamic. The simple truth is there is no modeling out there to follow that has been tested enough to have confidence in sub 100 meter dives. We can see that by using many of the models we currently use that we have an extremely low incident rate. Incident rates are between 1-9 for every 10,000 dives depending on what source you consider. Still impressive numbers even at its worst prediction. But those numbers go out the window as we go deeper than 100 meters.

    So understand that no bubble model is fool-proof, but stretching any model beyond 100 meters is going beyond its predictive value. We may not have all the answers about where to take things, but it's a common knowledge that following the current models beyond 100 meters will not achieve the best results.

    There are people applying their recipe on how to bend that curve, but the ones that know anything about it will not share it with just anyone, especially on the internet. :)

    Hope that answers your question.
    I'm not sure people should be paying money on how to 'bend the curve' on extreme dives from someone that doesn't seem to get bulhmann isn't a bubble model.

    I love reading about extreme dives like your current project. I was registered on this forum before I'd done my open water to read Dr Mikes trip reports but this seminar seems like N=1 experiences of surviving (which while fascinating) is being promoted as scientific fact.

  3. #63
    So many CCR So little etc Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase's Avatar
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    Re: "Long" bottom times below 100m

    No one really "bends the curve" in any productive way.

    It’s all just voodoo to make themselves feel better after the dive.

    You can't alter the deco model based on a handful of dives where there was no baseline for the dive its self.

    "O I extended the mid stops and felt so much better" is the kind of crap we all fell for when GI III was telling us to "just do the deep stops and the shallow stops won’t matter" and "Spread half the shallow stops across the deep stop time and you will be running marathons post dive"

    All now proven to be totally misguided at best and yet no one could argue the man was doing the dives and should have had more data than we as merely recreational once a week divers get.


    What you had for breakfast is probably just as important as what deco curve you use but what has been showed was in the best attempt at a pier reviewed scientific experiment in decompression, deep stop profiles fared less well than shallow stop profiles.


    The mere fact we as CCR divers need to get shallow fast to conserve bailout gas, makes this a day to celebrate.

    A: We can conserve gas
    B: We can modify the profile on the fly

    It is simply not possible to properly modify a VPM or RGBM type profile mid dive. You can carry bailout tables but as I have already demonstrated VPMB 0 costs considerably more deep bailout gas than the equivelent Bhulman 100/100GF profile

    If you plan 100/100 GF its very easy to say on the day "oh look I have plenty of gas because I am not breathing 40RMV so ill alter that plan to 70/70

    Just follow the real-time GF display on your Shearwater

    You haven’t got the equivelent on VPMB or RGBM

    So OK let’s say you do carry VPMB 0 bailout tables but you run out of deep gas? Obviously you have to blow off stops deep to save gas but then how do you compensate for this on your deco profile after the event?


    And following tables is task loading


    When I plan a deep dive I have one single figure in my mind

    The first stop depth for a 100GF profile

    If the poo hits the fan that’s all I have to focus on.


    Some will argue about planning training and buddy’s meaning you can do X Y Z in the event but IMHO none of us dive enough or train hard enough to make that a guaranteed result.

    I have seen divers lose it and shoot up from great depth and I have yet to see a buddy follow them

    So bearing all that in mind the whole issue of bubble models goes away for me. The only remaining question is what GF profile to dive.

    I have dived them ranging from 10/125 to 20/80GF but if you follow current thinking the proper way would me more like 70/70

    I have been moving in this direction for over a year now and I am up to 60/80

    So far so good

    But then again all the others worked as well.

    Problem is I have no real way of knowing body stress. So I am reliant on people who have done the research telling me I am doing the right thing

    I have been diving for 27 years and I have tried just about every new-fangled deco system and computer out there.

    If someone I trust in the future comes up with a bigger and better pier reviewed paper than the last one I’ll probably try that as well

    ATB

    Mark

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    Re: "Long" bottom times below 100m

    Quote Originally Posted by Mark Chase  View Original Post

    Some will argue about planning training and buddy’s meaning you can do X Y Z in the event but IMHO none of us dive enough or train hard enough to make that a guaranteed result.
    +1

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    Re: "Long" bottom times below 100m

    Nice write up, kind of covers it all regarding BO


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  6. #66
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    Re: "Long" bottom times below 100m

    We have scientists like David Doolette saying we don't know the cause and effect of decompression stress beyond well tested models. I am always cautious when someone states they are modifying deco tables successfully based on "experience". Scientific research and hard data points are the only real truth, everything else is highly anecdotal.


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    Re: "Long" bottom times below 100m

    Looking forward to getting good scientific data for dives beyond 100 m. Unfortunately, there isn't, yet.

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    Re: "Long" bottom times below 100m

    Quote Originally Posted by dreamdive  View Original Post
    Looking forward to getting good scientific data for dives beyond 100 m. Unfortunately, there isn't, yet.
    And there won't be..
    because who would be supposed to fund that for what interest for what group?
    Rec diving deco science has always been piggy backing on results from military or commercial activities..


    Quote Originally Posted by Garethingham  View Original Post
    We have scientists like David Doolette saying we don't know the cause and effect of decompression stress beyond well tested models. I am always cautious when someone states they are modifying deco tables successfully based on "experience". Scientific research and hard data points are the only real truth, everything else is highly anecdotal.




    No one is gonna fund science for some "crazy" divers trying to push the envelope..


    So yes scientific data would be appreciated, but it will not be there so all you can do is work from "experience" and this will be highly anecdotal..


    Talking about anecdotal.. The whole Deep Stop strategies were based on nothing else than anecdotal based theory and experience with it and changed the deco approaches for more than a decade..
    Today even almost any pure rec diving computer has implemented deep stops..


    tec rec trimix diving is solely based on experience and anecdotal data.. Bühlmann only theoretically implemented Helium half times into the modell.. all real life testing was based on Air ie. Nitrogen only.
    all bubble models are purely anecdotal anyways..


    All nowadays tec rec diving to the 100m realm is mostly not supported by any scientific research for that area (I gladly stand corrected if I missed something)..
    It is just that in the meanwhile with ADv Tx going more and more mainstream that much more real life experience is there and it seems that the current approaches out there seem to work pretty well..
    At least I am not aware of any increased amount of "unexplained" decompression issues in comparison to the regular rec dives within NDL..


    So I am not sure I get your point Gareth, are you saying lets stop diving past 40m and with Trimix as there is no scientific research in that realm?

  9. #69
    RBW Member rjack will become famous soon enough rjack will become famous soon enough rjack will become famous soon enough rjack's Avatar
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    Re: "Long" bottom times below 100m

    Quote Originally Posted by Garethingham  View Original Post
    We have scientists like David Doolette saying we don't know the cause and effect of decompression stress beyond well tested models. I am always cautious when someone states they are modifying deco tables successfully based on "experience". Scientific research and hard data points are the only real truth, everything else is highly anecdotal.
    And the same people are saying that for any given model the DCS probabilities past 100m are greater than at shallower depths. That's based on actual data. So if anything I'm assuming that the modifications Peter is talking about are being done to try and make schedules more conservative, not less like in the olden GI3 days.

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