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Change in buoyancy from 12l to 15l cylinder

Discussion in 'Basic Scuba Discussions' started by BlueTrin, Apr 9, 2019.

  1. BlueTrin

    BlueTrin DIR Practitioner

    # of Dives: 100 - 199
    Location: London
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    Is there a rule of thumb about how much weight less you need to use if you equip a 15l stew vs 12l steel ?

    It is obviously heavier but it is slightly bigger as well and will have more air meaning that you have even less weight when empty.
     
  2. RyanT

    RyanT Solo Diver

    # of Dives: 500 - 999
    Location: Maryland
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    Not really. For example a LP and HP tank that have the same water capacity will have different buoyancy characteristics. Likewise, different manufacturing processes can influence the buoyancy of a given sized tank. Your best bet is to dig around for charts that give this information. Even the charts are often just a starting point though. It's just something you have to work out for yourself.

    Here's information for Faber

    Blue Steel Scuba - Cylinder Specs
     
    Zef and BlueTrin like this.
  3. EireDiver606

    EireDiver606 DIR Practitioner

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    Simple,don’t dive a 15l!

    They’re heavy, uncomfortable, and unbalanced
     
    Zef likes this.
  4. ljpm

    ljpm Barracuda

    # of Dives: 50 - 99
    Location: Ottawa, Canada
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    I disagree. But then I'm 1.96m, 118kg. A 15L fits me as well as a 11L Al fits the average diver.
     
    wKkaY and Fibonacci like this.
  5. Mike1967

    Mike1967 Manta Ray

    # of Dives: 100 - 199
    Location: Victoria, Australia
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    Not sure about your tanks over there but with our Australian tanks the 15lt is only .25kg more negative than our 12.2lt.
     
  6. Fibonacci

    Fibonacci Manta Ray

    # of Dives: 500 - 999
    Location: Melbourne, Australia
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    EireDiver606 likes this.
  7. Mike1967

    Mike1967 Manta Ray

    # of Dives: 100 - 199
    Location: Victoria, Australia
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    Sorry, I left out the empty part lol
    Buoyancy difference empty is the figure you need to worry about when working out the difference in lead to carry, and that's .25kg
    I carry the same for both tanks.
     
  8. Fibonacci

    Fibonacci Manta Ray

    # of Dives: 500 - 999
    Location: Melbourne, Australia
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    Aha :D
     
    Mike1967 likes this.
  9. BurhanMuntasser

    BurhanMuntasser Dive Charter

    # of Dives: I'm a Fish!
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    Folks, note that the specs of the tanks in the EU/UK where the OP is are usually different from those in the US.

    I use less lead with my 12L short and heavier tanks than with my 15L tanks!! (both are 230 Bar).
     
    Vicko likes this.
  10. Storker

    Storker Divemaster

    # of Dives: 100 - 199
    Location: close to a Hell which occasionally freezes over
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    The internal volume is 3L larger, so add 3kg to your belt. Then subtract the weight of the 12 from the weight if the 15 (it should be stamped on the shoulder of the tank), and divide by 7.8. What you get is the difference in steel volume. Take that number of kg off your belt.
     
    Magnus Lundstedt likes this.

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