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Cave Fills on LP tanks

Discussion in 'Technical Diving' started by ScubaFeenD, Oct 15, 2010.

  1. Superlyte27

    Superlyte27 Cave Instructor

    # of Dives: 5,000 - ∞
    Location: Florida
    4,160
    3,318

    Well of course... You're taking 3 tanks instead of 2.
    If you are talking 85's and a stage 80, that's nearly 50cu' more air than just twin 104's alone.
     
  2. ucfdiver

    ucfdiver DIR Practitioner

    # of Dives: 500 - 999
    Location: Orlando, FL
    3,338
    501
    LP85x2 = 230 @ 3600psi
    LP104x2 = 282 @3600

    When you add a stage to the LP85's (77cu ft), it's actually 18 cuft more (that's 6cuft from 1/3rds!), less than 100psi difference in backgas, which is within the margin of error of the SPG, and therefore statistically insignificant.

    Could you explain how you got 50cuft?
     
  3. Superlyte27

    Superlyte27 Cave Instructor

    # of Dives: 5,000 - ∞
    Location: Florida
    4,160
    3,318
    First, my 85 is 85cu' at 2400psi, not 2640.

    And secondly, even at your "new" math, 20cu' is 20cu' and you'd be hard pressed to convince me that 3 tanks through the water is less drag than 2 tanks. But, i'm guessing you went to UCF. I myself went to UF.

    And are you really only filling an AL80 to 3000cu' to account for that 77.4cu'?
     
  4. BCSGratefulDiver

    BCSGratefulDiver Mental toss flycoon ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: On the Fun Side of Trump's Wall
    80,691
    69,697
    Overfilling steel tanks is pretty common practice. Among our tech group we have a saying that "when your tanks are full it's time to turn the dive" ...

    ... you can do the math ...

    ... Bob (Grateful Diver)
     
    RayfromTX and shoredivr like this.
  5. Superlyte27

    Superlyte27 Cave Instructor

    # of Dives: 5,000 - ∞
    Location: Florida
    4,160
    3,318
    I remember my first dive with Green_Streak from this forum. We get to N. Florida for a cave dive, and the shop asks how much air we want in the tanks. Green says, "put 4000 in 'em".

    I thought he was kidding.

    We get into the water later that night in Ginnie and I've got a cold 3850 in my LP95's.
     
  6. BCSGratefulDiver

    BCSGratefulDiver Mental toss flycoon ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: On the Fun Side of Trump's Wall
    80,691
    69,697
    ... I'd be a lot more reticent about overfilling aluminum tanks than steel ones ... even if they can take it, I doubt they'd survive more than one or two hydro cycles before they ended up as scrap metal ...

    ... Bob (Grateful Diver)
     
    shoredivr and Bowers like this.
  7. ucfdiver

    ucfdiver DIR Practitioner

    # of Dives: 500 - 999
    Location: Orlando, FL
    3,338
    501
    Wish you could have taken a class on context while you were there. Seeing as how overfilling is the whole topic of discussion. But hey, if my math was that wrong, I'd stick my head in the sand and pretend I didn't know either.

    AL cracks/shatters, steels can expand/contract before tearing. This is day 1 stuff of a cave diving course, no?

    You could always *gasp* try it, rather than e-diving? Didn't you just recently learn to trim out doubles in a common NFL rig? Why not learn this, too? :idk:
     
  8. LiteHedded

    LiteHedded Contributor

    4,075
    922
    there's your problem


    i consider these things disposable. no big deal if they dont pass a hydro down the line. take the kit and the valve off and buy a new one
     
  9. Superlyte27

    Superlyte27 Cave Instructor

    # of Dives: 5,000 - ∞
    Location: Florida
    4,160
    3,318
    I'm asking you, do you really only fill to 3000? I usually fill to 3400. Haven't scrapped any of my 6 AL's yet

    As far as trimming a cave rig... I've got more dives in a transpac than you have underwater. I liked it. But, sitting on my butt for half a decade I gained some weight and transpac didn't work for me anymore. It was time to move on. No matter what happened, new rig and LP95's didn't work without adding 3lbs to the tail of the rig. Adding weight is dumb. I swapped out for LP104's and my trim is exactly spot on. Lets go diving one day, we can compare notes, and either one of two things will happen, we'll become friends or we'll fight, either way i'm good with it. Let me know.
     
  10. Superlyte27

    Superlyte27 Cave Instructor

    # of Dives: 5,000 - ∞
    Location: Florida
    4,160
    3,318
    LiteHedded:

    I got a full scholarship to both schools I applied to. UF was one, and Stetson University was the other. Being married with 3 children I opted for the cheaper route as Stetson would suck up every penny of money and UF only sucked up 25%. If I had it to do all over again I would have went to Stetson. I hate UF
     

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