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Thread: Why can't I dive twice on the same tank?

  1. #11
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    I run out of time not air

  2. #12
    Registered Users bottlefish's Avatar
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    I think that member of your dive group needs to take a step down. Relying on one person, expecting one person to have all of your problem solutions up their sleeve can be dangerous in it self. What's the plan if it's you that had gas problems. Also, what if you weren't close enough to the problem to assist, had to bail early from the dive for whatever reason and so not even there etc.

    Seasnake makes a valid point, we are all spare air carriers for each and every one of the other people we dive with, in case they have major problems with air supply and we're the ones that have to assist. So we should always have enough air left in our cylinder to get us and An Other to the surface safely in case of problems. Provided you have this, then obligation sorted... assuming you are running on a no deco schedule, then not too hard to manage.

  3. #13
    Wreck Diving Moderator acelockco's Avatar
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    FYI,

    On New Jersey Dive boats, MANY of the divers use doubles, and do two seperate dives on the same cylinders. I thought it was strange as well, but even on their second dive, they start off with more air than I have in my al80.

  4. #14
    Master of Mask Mold seasnake's Avatar
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    Quote Originally Posted by acelockco View Post
    FYI,

    On New Jersey Dive boats, MANY of the divers use doubles, and do two seperate dives on the same cylinders. I thought it was strange as well, but even on their second dive, they start off with more air than I have in my al80.
    I do that, but I think it's more out of laziness ... so I don't have to switch tanks between dives ...

  5. #15
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    Even if I use my tank twice, I still have enough for my buddy, and more. So I'm fuming about the fact that someone is suggesting that I have to carry all that air to literally be an air-wetnurse for a bunch of potential idiots. In that line of logic: how long is my safety stop supposed to be exactly? 1hr until everyone is out of the water?

    As for the doubles: how do you get out of the water with all that weight?!

  6. #16
    Registered Users bottlefish's Avatar
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    Hmm, re-educate, or find a new dive team :-)

    Getting out of the water for doubles? Ah, well that sort of divings not for women really, they're too weak and fragile... OK, that was in bad taste (sorry!).

    It does take a bit more care, but not as hard as you might imagine. Plus, if you're air is as good as you say, then there's no need for you to double on 12 litre cylinders, take a couple of tens or eights instead.

  7. #17
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    My air management is ok so I haven't really thought about it until now. I average about 2/3 -1/2 an 80 for all of my dives so far. I haven't taken any of those clinics or courses but I'd like to.

  8. #18
    Wreck Diving Moderator acelockco's Avatar
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    Now I am confused?

    It shoud be a rare time when you can reach your NDL on an AL80 and a non repetative dive. Is there something I am missing? Are you VERY VERY SMALL? Like 4'5" 70lbs?

    What is your avg. dive depth and bottom time? I am just trying to figure this out.

  9. #19
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    I'd like to be closer to 70lbs The closer you are to weighing 0lbs the better right? At least that's the impression I'm getting from the Victoria Secret Fashion Show

    A sample dive would be: penetration would range from 90-70ft inside the wreck depending. So a 45/50-min dive (quick decent down the line and the requisite 3-min safety stop) I would be getting back on the boat with 2100-2250psi with a starting pressure of abt 3150psi. 2nd dive, same profile, same tank and surfaced just under 1000psi w/ a starting fill of 3150psi on an 80. Non-penetration, on the same wreck with quite a bit of swimming around, I would surface w/ abt 1600+, maybe more. I'm not quite sure b/c the non-penetration dives are done on a mixed boat and I'm always sharing my octo w/ someone. (Which is scary b/c they really suck the air back).

    So if there's a lot of current or swimming I definitely would not do 2 dives on 1 tank.
    Last edited by littleleemur; 12-17-2007 at 04:27 AM.

  10. #20
    Wreck Diving Moderator acelockco's Avatar
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    Are you missing a lung?

    Either you are pulling my chain or you might be the record holder for the least air consumption! At 90 feet, I doubt I would even get 45 minutes out of an 80 cubic foot cyl. You are saying you get 100 minutes with 1000 psi to spare, that does not compute to me.

    Maybe I am missing something.

    Now I have no idea what you are talking about "alyays sharing an octo", it is for an emergency, not for always use.

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