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Thread: Will OC records always be deeper?

  1. #31
    New Member Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell's Avatar
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    Re: Will OC records always be deeper?

    Quote Originally Posted by Abbo  View Original Post

    Is there a sweet spot?
    Where does it end?
    What ends it?
    Abbo,

    Depth limitations for bounce dives on CCR will likely come from work of breathing issues, or HPNS in vulnerable individuals. Or an interaction between the two... because reducing gas density to avoid work of breathing problems will involve reducing the nitrogen content, and reducing the nitrogen content may provoke worse HPNS. The actual depth where the diver can achieve no more work than the work of breathing alone will depend to some extent on the equipment used and its set up, so it will be variable. If you read our paper on David Shaw's accident it explains the physiology of the limitations imposed by work of breathing. If you pm me I will send you a copy.

    Warm regards,

    Simon M

  2. #32
    RBW Member Hagal7 is an unknown quantity at this point Hagal7's Avatar
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    Question Re: Will OC records always be deeper?

    Quote Originally Posted by Meerveld  View Original Post

    I consider that any World depth records would be best attempted on a combination of OC and CC. Utilising OC for the rapid descent and initial ascent. Switching to CC at the first deco stop to optimise decompression and minimise gas usage.
    Hi, this is wonderful idea, but: Is there any deco software able to count that profile OC down + CC up? Are any data about that kind of diving?
    Greetings
    Mark

  3. #33
    Aviator, diver & sailor Meerveld is an unknown quantity at this point Meerveld's Avatar
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    Re: Will OC records always be deeper?

    Quote Originally Posted by Hagal7  View Original Post
    Hi, this is wonderful idea, but: Is there any deco software able to count that profile OC down + CC up? Are any data about that kind of diving?
    Hi Mark,

    I use DecoCheck, it enables you to switch between CC and OC and back again at any point with any gas mix or setpoint you desire. After calculating the deco obligations it warns you of risks related to PPO2, PPN2, ICD and tells you the amount of gas required based on the size of tanks and SAC Rate you specify.

    For a standard dive I input my desired depth and profile and then assume my CCR has failed at the worst possible moment, typically the end of the bottom time. I then switch to OC and calculate the deco obligations. I then play with the gas mixes, size and number of bailout tanks to enable me to carry the smallest/least number of bailout tanks that provide me with enough OC gas to complete all deco obligations (full redundancy).

    For the deep dive you desire I would reverse this process, descending rapidly on OC and then switching to CCR at the first deco stop. Then playing with the setpoint to find a compromise between minimising deco time and controlling OTU and CNS exposure. Further optimisation could be done by setting a high setpoint for the short deep stops (minimising on-gassing) and then bringing the setpoint down for the long shallow stops (minimising OTU and CNS exposure).

    Mark Ellyatt has spent the last four years helping develop the DecoCheck software specifically for deep/long dives.

    Check it out at: DecoChek Decompression Software : Welcome

    I do not know of anyone who has used this combination on a record attempt yet. The deepest SCUBA records have all been set on OC and I believe that several deep record attempts using just CCR's have resulted in fatalities (Mark Ellyatt mentions three on another thread).

    At these kinds of depths you are flying blind. So few dives have been done on SCUBA to these depths that there is not enough data available for statistically valid analysis. All anyone, or any software can give you is their best guess based on extrapulating of data gathered at much shallower depths.

    Regards,

    Carl

  4. #34
    SiegeEngine II Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon has a reputation beyond repute Mdemon's Avatar
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    Re: Will OC records always be deeper?

    Quote Originally Posted by Hagal7  View Original Post
    Hi, this is wonderful idea, but: Is there any deco software able to count that profile OC down + CC up? Are any data about that kind of diving?
    Greetings
    Mark
    VR£, X1 etc will do it on the fly.

  5. #35
    Temp Read Only Mode ccr_ada is just really nice ccr_ada is just really nice ccr_ada is just really nice ccr_ada is just really nice ccr_ada is just really nice ccr_ada is just really nice ccr_ada is just really nice ccr_ada is just really nice ccr_ada is just really nice ccr_ada is just really nice ccr_ada's Avatar
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    Re: Will OC records always be deeper?

    Quote Originally Posted by Mdemon  View Original Post
    I'm surprised no ex-COMEX employees have ever ended up on here. I guess doing it for a living has put them off doing it for fun.
    The is

    ja

    Jon Adams

    He dived with Comex as a diver ;)
    And he still likes any sort of diving especialy nice deep virgin liners

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