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NDL's

Discussion in 'Computers, Gauges, Watches & Analyzers' started by HeatCker, Oct 2, 2017.

  1. Clark Fletcher

    Clark Fletcher Contributor

    # of Dives: 25 - 49
    Location: Hickory, NC
    215
    88
    Do you know if the PADI tables originally came from the USN tables as well? I've heard someone say that before. And since PADI was started by a NAUI instructor it seems logical that they would have started out with the same tables.
     
  2. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
    18,454
    10,816
    no, completely different studies. PADI commissioned the research work for that
     
  3. HeatCker

    HeatCker Solo Diver

    238
    35
    thanks guys for all the input, appreciate it
     
  4. 2airishuman

    2airishuman Solo Diver

    # of Dives: 100 - 199
    Location: Greater Minnesota
    2,607
    1,865
    For two reasons:
    1) There hasn't been enough research into extremely long, shallower dives to be able to determine whether the models remain valid.
    2) Recreational dives longer than 3 hours are rare.

    If you're diving according to the PADI tables, the instructions are to treat dives shallower than 35' as 35' dives.

    If you use software like Subsurface you can experiment with the algorithms. Depending on your choice of algorithm and gradient/conservatism factors, you may find that there is no NDL at 15 or 20 feet. I don't know whether or not such dives would be safe. I have an Oceanic Geo also but would not attempt a really long dive without more research.

    FWIW dives of this duration aren't very practical on SCUBA but could be achieved with hookah systems.

    There is a body of research on altitude sickness that is the flip side of the coin and may be of interest.
     
    oly5050user likes this.
  5. oly5050user

    oly5050user Dive Travel Professional

    # of Dives: 5,000 - ∞
    Location: Westchester NY
    4,131
    892
    Not completely true. Ages ago PADI originally used a dive table that used a 120 minute half time same as NAUI, USN..that table worked fine for the time, but was restrictive on REPETIVE dives that RECREATIONAL dives do, this table did not consider a diver nitrogen free until 6 half times (12 hours) have passed. PADI commissioned DSAT to study and form the RECREATIONAL DIVE PLANNER ( RDP ) to address the issue. The RDP considers a diver nitrogen free after 6 half times have passed as well , but based on a 60 minute half time rate (6hours).
     
  6. BoltSnap

    BoltSnap Dive Charter

    # of Dives: I'm a Fish!
    Location: Nomad
    6,738
    2,797
    I stopped using dive tables and started using computers exclusively for my recreational diving in 1987. The only time I use tables is when I am teaching dive tables use to my students.
     
  7. Clark Fletcher

    Clark Fletcher Contributor

    # of Dives: 25 - 49
    Location: Hickory, NC
    215
    88
    I hope this isn't too off topic here and I'm kind of thinking out loud. Would staying overnight in Jules' Undersea Lodge in Key Largo be the equivalent of 24 hour dive at 30 feet? (Assuming you were in the lodge for 24 hours)
     
  8. RyanT

    RyanT ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Maryland
    2,233
    2,095
    Yes.
     
  9. Sevenrider860

    Sevenrider860 ScubaBoard Sponsor ScubaBoard Sponsor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Newnan, GA
    799
    431
    Closer to 12 hours at 20 feet. The deepest I have ever recorded at Jules is 26 feet. I am not sure where the 30 foot depth can be achieved. I have looked through the window of the lodge a few times and I can't imagine anybody spending a full 24 hours in there!
     
  10. Clark Fletcher

    Clark Fletcher Contributor

    # of Dives: 25 - 49
    Location: Hickory, NC
    215
    88
    Good point. I was going by the depth that they list on their web page. But, I did five dives there and the absolute deepest my dive computer saw was also 26 feet. And, on more than one dive we swam under the lodge.

    Anyway, the reason I felt this tied back to the original question by the OP is that if we assume the lodge's moon pool is at 20 feet, then staying in the lodge for 12 hours would be the equivalent of a 12 hour dive at 20 feet. Since you don't have to decompress after staying in the lodge overnight (at least it doesn't say anything to that effect that I can find), it seems to support the notion that above a specific depth, there would be no decompression limits. Unless I'm completely missing something here.

    Edit: May as well ask this question here. Is it worth taking the PADI Dive Theory course?
     
    Last edited: Oct 3, 2017

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