• Welcome to ScubaBoard


  1. Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

    Benefits of registering include

    • Ability to post and comment on topics and discussions.
    • A Free photo gallery to share your dive photos with the world.
    • You can make this box go away

    Joining is quick and easy. Login or Register now by clicking on the button

Optimal Buoyancy Computer

Discussion in 'Advanced Scuba Discussions' started by rsingler, Mar 23, 2019.

  1. RTC'83

    RTC'83 DIR Practitioner

    # of Dives: 25 - 49
    Location: North Texas
    212
    97
    28
    Thanks for sharing, amazing tool!
     
    rsingler likes this.
  2. David Novo

    David Novo Nassau Grouper

    # of Dives: 50 - 99
    Location: Porto, Portugal, Europe
    104
    18
    18
    After doing some calculations for drysuit with single 15l steel tank or twins of the former, it always results in a 40 lbs lift being enough (after ditching some weight in either a wing failure or drysuit flood scenario). Does this make sense (same lift for single or twins, not same wing)?
     
  3. Mike1967

    Mike1967 Manta Ray

    # of Dives: 50 - 99
    Location: Victoria, Australia
    889
    368
    63
    As long as you're not over weighted, it does.
     
  4. David Novo

    David Novo Nassau Grouper

    # of Dives: 50 - 99
    Location: Porto, Portugal, Europe
    104
    18
    18
    Yet I see a significantly number of posts claiming that 30 lbs is enough for cold water diving. How?
     
  5. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,563
    4,064
    113
    I'm guessing that those that claim that are depending much more on reserve suit buoyancy, or partial air trapping in a wing failure. The spreadsheet is fairly conservative in its estimate of reserve drysuit lift. It's likely that from experience, some folks use that lift without thinking about it.
    And in the case of suit flooding or a wing tear, it should be easily possible to trap 10# of lift in a leg or other intact suit area. It's less true, but still possible with a wing, also. The tool presupposes total loss of lift, as noted in the manual.
    It's all a question of how close to the limit you want to be. The Lift page should map that out, so you can see the instances in which you'd be -10# or more and having to depend on imaginative redundant lift.
     
    David Novo likes this.
  6. David Novo

    David Novo Nassau Grouper

    # of Dives: 50 - 99
    Location: Porto, Portugal, Europe
    104
    18
    18
    Thank you for the clear explanation.
     
  7. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,563
    4,064
    113
    It's not as though a possible drysuit lift formula error inside the spreadsheet could be a factor in this particular issue. Once you remove drysuit lift from the equation (whether or not it was calculated correctly) then residual lift is pretty easy to determine. There's a little bit from some neoprene pieces (hood and gloves) that may be compressed at depth. There is your stated wing lift from the manufacturer. And that's about it. It's enough to offset your tanks, bands and backplate, or it's not.
     
  8. David Novo

    David Novo Nassau Grouper

    # of Dives: 50 - 99
    Location: Porto, Portugal, Europe
    104
    18
    18
    That is true, but according to the spreadsheet, if you dive with the majority of the lead on a weight belt, you can get away with a 30lbs wing, without relying on trapped gas.
     
  9. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,563
    4,064
    113
    That change in required weight is due to a separate issue.
    You only need 30lb of lift total, for the setup you have entered. That includes baseline drysuit lift, (which will float your weight belt and you, out of your rig).
    However, your rig apparently will not float itself with all your weight in the backplate, with a 30# wing.
    By transferring some weight to a weight belt from the rig, your rig will float itself on the surface if you have to shed it, and the wing lift now just reflects what is required to float your entire setup, rather than extra lift required to float the rig when you don't have your drysuit helping.
     
  10. HKGuns

    HKGuns Barracuda

    # of Dives: 0 - 24
    Location: Merica
    202
    203
    43
    @rsingler I sense something is wrong in V.58.....I have been using V.57 and the results are quite different.

    The difference in my case seems to be V.58 says my Faber FX80 "Sum of Tank Buoyancy" is -1.7 whereas V.57 has it at -7.2.....Not sure which is correct, but it seems too large a difference. The resulting end values for weights to add are V.58 16 pounds vs. V.57 11 pounds. Thinking a 5 pound difference, all else being equal, version to version is too much.

    Just trying to help, not criticize. I went over everything several times to ensure my values were correct on both sheets.
     

Share This Page