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Optimal Buoyancy Computer

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

  1. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,536
    4,024
    113
    Than you so much for contributing your data! This will really help as we fine tune the program. I'll look at your numbers and get back you you by PM.
     
    Doctor Rig likes this.
  2. Snodge

    Snodge Angel Fish

    # of Dives: 100 - 199
    Location: BC
    15
    6
    3
    check cell E18 on "drysuit" tab seems it should be "=e15+E16"
     
  3. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,536
    4,024
    113
    Will do, thanks!
     
    Doctor Rig likes this.
  4. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,536
    4,024
    113
    @Snodge , thank you for your detective work! This is truly a joint project.

    Your pickup is correct. There's an error in cell E17 in the Drysuit tab.
    It has been corrected.
    Spreadsheets v68 have been loaded in Post #1.
    Thank you, @Snodge !
     
    Doctor Rig likes this.
  5. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,536
    4,024
    113
    Looked at your numbers, and while I haven't finished, they revealed another spreadsheet error, in the Lift Tab. Right now, it looks like a 2.2# error that puts the results much more in line with what you found experimentally.

    Readers: note that Lift tab cells B10:F10 have an incorrect formula for Fresh water only.

    I will continue going through @gr8jab 's data, and load new spreadsheets as soon as I finish looking for errors based upon what he found.
    Thank you @gr8jab !
    More to follow.
     
    Doctor Rig likes this.
  6. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,536
    4,024
    113
    Thanks to @gr8jab , we have been able to discover and correct two more small errors in the spreadsheet.
    Formula errors were corrected in Lift tab B10 thru F10, and in four similar hidden cells.
    The errors only affected fresh water divers, and did not account for personal buoyancy in those cases.
    Versions 69 have been uploaded into Post #1.

    Thank you again to our community!
    Bit by bit, we'll perfect this!
     
    couv and FreeFlyFreak like this.
  7. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,536
    4,024
    113
    For those of you who are inclined to follow @gr8jab 's lead and really test out the predictions...

    Okay, I'll start over. For the ONE GUY who's inclined to do this too :wink:, here's an answer to one of @gr8jab 's conundrums: "estimating 1/3 full lungs". From reading the manual, you know that much is dependent upon the change in buoyancy between full and empty lungs. Indeed, experienced open circuit divers use that very fact to glide up and over coral heads as they explore, because of the significant (>6lb!!) buoyancy change between full and empty lungs. By inhaling and exhaling, they can instantly change their buoyancy without messing with their bcd.

    In order to standardize measurements, we calibrated the formulas for "end-exhalation". For those who aren't familiar with the respiratory volume diagrams, it isn't clear whether that "means breathe out everything you can" or something else. As a result, in the manual we described it as 1/3 full lungs. Close enough for government work. But for an intense numbers guy like @gr8jab , that meant trying to figure out how much was 1/3 full.

    What we meant in using that term was: breathe in naturally, then breathe out. At the point where you stop a natural, relaxed exhalation, you're at "1/3 full". Now move on in the test. Many of you will recognize that you've still got volume left to blow out, in case you were inflating balloons for your daughter's birthday party, but that's not what we meant.

    Hope this helps as you measure your Personal Buoyancy in a pool.

    Why do all this in the first place? Especially when you can just do a buoyancy check in the ocean before you drop!
    Well, part of the value of this tool, wholly apart from calculating how much weight you might ditch for self-rescue, is having an easy way to shift gears when you buy new wetsuit, or when you shift from your usual Great Lakes steel tanks to Caribbean aluminum rentals, or when you want to start using a completely different setup and would like to arrive for your first dive a bit more prepared. Barring signifcant personal weight change, one personal buoyancy check will last through lots of rig changes.

    Dive Safe!
     
    couv and FreeFlyFreak like this.
  8. FreeFlyFreak

    FreeFlyFreak Solo Diver

    # of Dives: 25 - 49
    Location: California
    515
    671
    93
    Line 17 of the wetsuit tab "change depth here" does not work correctly. Should be able to just type in a number, instead it brings a drop menu "full farmer shorty"
    Worked fine in version 57
     
  9. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,536
    4,024
    113
    Thanks! I'll check it out soon!
     
  10. FreeFlyFreak

    FreeFlyFreak Solo Diver

    # of Dives: 25 - 49
    Location: California
    515
    671
    93
    Not sure how it works for anyone else but the suit buoyancy seems way off for me.

    To get the calculator to come up with the amount of weight I actually use diving cold I have to enter 6mm full only, nothing else that I wear, everything is close to new. That gives 10lbs of lead, with my tank, SS plate and 1st stage. 10lbs is what I use.


    I actually wear 8/6/5 full with a 7/5 hooded vest, plus 5mm boots and 3mm gloves. If I enter that, it gives 23lbs needed! 13 lbs more lead than I actually use.
     

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