Big Mistake

Discussion in 'Basic Scuba Discussions' started by DameDykker, May 13, 2003.

  1. DameDykker

    DameDykker Barracuda

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    Location: Copenhagen, Denmark
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    Bantering and flames aside - I at least learnt something. Most of my dives are long duration very shallow depth and I weren't aware that the SUunto algorithme was working in precisely that way. And I might very well not have found out before doing a deep dive - even though I would have checked the manual.

    So in conclusion I learnt from the internet (most classes have theory included). And I don't think I would have picked it up anyware else.

    So thanks to Seajay for sharing. And thanks to the rest of you for making the lesson more complete. :eek:ut:

    I hope that others will also make their misktakes puplic - It not that we havn't all make mistake one time or another.

    Take care down there :)
     
  2. ericfine50

    ericfine50 DIR Practitioner

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    I can't believe I am going to do this, but - SJ _ don't dive the computer, dive your plan. Going from 70 to 98 back to 70 is a continuation of the dive.

    Eric
     
  3. Scubaroo

    Scubaroo Great White

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    Suuntos are very conservative computers - see if you can track down Rodale's reviews on computers and conservatism, they're right down there at the "safe but short dive" end of the scale. My buddy's Cochran will often have NDLs of 10 or 15 minutes longer on the second dive, but we always surface according to the most conservative computer as a buddy team.

    Good thing about the Suuntos though is that they really push you towards using them as a bottom timer instead to get around the conservatism :tease: Planning on taking that route.
     
  4. Scubaroo

    Scubaroo Great White

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    Maybe the wind was blowing your boat?

    :confused:

    For the record, it's been checked - Nanook is a unique user, and is not posting from the same machine or IP address of any other user on ScubaBoard. Please contact Nanook privately if you wish to establish his/her identity.
     
  5. Scubaroo

    Scubaroo Great White

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    Actually your first and last posts in this thread have the same IP. The host is also logged.

    Sure someone could log in from a different machine. Ask Nanook directly yourself.
     
  6. Scubaroo

    Scubaroo Great White

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    !!!!!!!!!

    People, get yourself under control.

    Certain links are being edited out of this thread. They have no place on ScubaBoard.
     
  7. Zagnut

    Zagnut Manta Ray

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    ..and you can tell me if this is a dumb question or not.

    Off gassing at your safety stop occurs during the process of breathing. If you slow your breathing down to conserve air on your safety stop, aren't you also slowing down the offgassing process? Wouldn't this increase the time required for the deco stop? It seems like conserving air at the safety stop would be detrimental to the whole deco stop process.

    Your thoughts please...
     
  8. Zagnut

    Zagnut Manta Ray

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    Anyone have any insight to my earlier post

    If I were in SeaJay's fins on this particular safety stop, I would have not conserved my air like SeaJay did. I would have breathed normally and sucked my tank all the way down to maximize the offgassing process... would this have been the right thing to do?

    Anyone?...
     
  9. kwesler

    kwesler Barracuda

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    to say this is the best thread I have read in a while-congrats to all for egos in check and focussing on the interesting, educational stuff!

    now, back to our regularly scheduled program!

    Ken
     
  10. Charlie99

    Charlie99 Orca

    # of Dives: 500 - 999
    Location: Silicon Valley, CA / New Bedford, MA / Kihei, Maui
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    Those computers have an assumed ascent rate for which the NDL is calculated. In all cases I know of, that ascent rate is much faster than the 8 feet per minute actually used by SeaJay.

    SeaJay -- if you look at decompresssion literature for stuff on "Hill vs. Haldane" you will see that your ascent profile is far from ideal.

    You would have done much better with a 30fpm ascent to an initial stop of a 1-2 minutes around 50' -- but I'm sure that you saw that when using V-planner, or any of the tested programs such as Decoplanner or GAP.

    Charlie
     
  11. Charlie99

    Charlie99 Orca

    # of Dives: 500 - 999
    Location: Silicon Valley, CA / New Bedford, MA / Kihei, Maui
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    I ran the depths/times SeaJay gave through the Dataplus simulator, which is probably the same deco model as your Aeris. It was down to 2 min NDL at 75' on the first dive, and either deco or within 1 minute on the 2nd.

    It's OK to push NDL limits or exceed them, provided that you have enough gas to properly decompress --- which wasn't done in this case. As you can see from the tissue sat charts, his medium tissues were still heavily loaded, even after his extended safety stop.

    Question 1. for SeaJay: why didn't you just share air for a while? That would have given you a slight additional deco edge since your buddy had 32%, and that would have left a bit more gas on your back to handle any problems while getting onto the boat.

    Question 2. Quite a few posts back, you made reference to 18 minutes of deco obligation while passing 45'. Was this really deco time, or was this a calculated "time to ascend" using the ultra slow ascent rate that you had at the time?

    Question 3. On the jpg images, the check box "tissue pressures invalid" is checked. Is that something you entered? Is that Suunto saying that the profile made their model invalid?

    Charlie
     
  12. Charlie99

    Charlie99 Orca

    # of Dives: 500 - 999
    Location: Silicon Valley, CA / New Bedford, MA / Kihei, Maui
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    I stand by my statement that the Aeris computers and the Oceanic DataPlus computers use the same model --- both are Dr Deco's M-values, same as PADI RDP. I didn't say that they were the same as Suunto's, which is another haldanean based model, with hacks to fudge in a bit of RGBM-like behavior.

    Charlie
     
  13. Se7en

    Se7en Nassau Grouper

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    I'm reading all the trolling and flaming, and have to admit I don't get it.
    A few minutes of deco, more or less, won't kill you. Drowning will.

    For rec dives like this, I'd dive my computer or my plan, or anything I felt like. BUT I'd make damm sure that I had enough gas to get me and my buddy back to the surface, with lots to spare.

    Seajay - you're a big guy. Stop putzing around with small singles and take enough gas so it's not a problem anymore. If you had been wearing double 80s, then the dive profile would not have been a concern at all.

    Se7en
     
  14. GearHead

    GearHead Manta Ray

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    Even those that use their Suunto's in gauge mode still have access to a valuable tool it provides: The Ascent Rate Indicator.

    I believe it's on the far right of all of their units (I've only got experience with the Mosquito and Vytec), and it's dead easy to use. At the end of your dive, I recommend that it's use to ensure that you're not going up too fast . . . or even too slow. :)
     
  15. GearHead

    GearHead Manta Ray

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    First: 6 knot current?

    SeaJay, I recommend you go to dictionary.com and look into the definition of the word "Hyperbole".

    Second, judging by this thread and past ones, it sounds like a number of people don't completely understand how the Suunto computers use the RGBM deco algorithm, and how to properly follow the computer's advice.

    Let me preface this by saying, I'm just a Suunto CPU user like a lot of others, and the following is what I've learned from reading the manual and using my CPUs (Mosquito and Vytec). Please correct me if I'm wrong.

    Suunto CPUs enter "deco mode" when one or more of your "tissue compartments" is saturated with Nitrogen in excess of 100% (theoretically). When this happens, and the CPU gives you a "ceiling", it's not saying "get to the ceiling depth asap and stay there until I say you're out of deco", it's saying "under no circumstance should you ascend above that depth until you've done more off-gassing and I say you are out of deco". A lot of important off-gassing happens below 10' and if you run some simulations using your CPU or Suunto Dive Manager software for a deco dive, you'll see that you can exit deco mode by spending time well below 10' and reducing the nitrogen load on the oversaturated compartments.

    To clarify: At any point during a dive, if you go into deco but subsequently ascend and get the particular tissue compartment(s) below 100% saturation, the CPU will go back into regular dive mode, and show you an NDL (no deco limit) instead of the ASC indicator. In fact, depending on your level of saturation, during a simulation, you'll see that the ceiling changes depths based on how saturated you are (deeper ceilings for more saturation).

    I wonder how many divers were unintentionally bent because they found that they accidentally entered deco and shot up too fast to "get to the ceiling". :( And before you get defensive, SeaJay, I'm not referring to you regarding ascending too fast, because you apparently didn't. But I do assert that you don't understand the "ceiling" concept based on your actions.
     
  16. GearHead

    GearHead Manta Ray

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    Thanks, I will.

    So how was my post non-productive? I'm trying to help you. If you're going to flip your dive-plan mid-dive and go to the computer, you should at least know how to use the CPU, don't you agree?
     
  17. Northeastwrecks

    Northeastwrecks Divemaster

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  18. Uncle Pug

    Uncle Pug Swims with Orca ScubaBoard Supporter

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  19. Uncle Pug

    Uncle Pug Swims with Orca ScubaBoard Supporter

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    that isn't a troll... he has a point... how can you and your buddy have different plans?
     
  20. Uncle Pug

    Uncle Pug Swims with Orca ScubaBoard Supporter

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    You are confused about *trolls*, *flames* and *sockpuppets* among other things (like *profile*.)

    Certainly the poster is a *sockpuppet* but just as certainly is not a *troll*.

    The post is legitimate (imo) and not merely inflamatory though it might be considered a *flame*.

    If your buddy *planned* his dive and dove his *plan* but that *plan* was simply to stick with you while you followed your *plan* then I think you are both confused about the word *plan* as well.

    Nanook's points 1-7 seem fair to me.
     

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