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Optimal Buoyancy Computer

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

  1. Doctor Rig

    Doctor Rig Nassau Grouper

    # of Dives: I just don't log dives
    Location: Michigan
    163
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    “Included is a 50-page user’s manual to lead you through the more complex parts of the tool, and a Quick Start section to get you going with minimal familiarity with spreadsheets. Additionally, the manual discusses the theory behind the more complex buoyancy calculations, whether you need help with Excel or not.“
    ————————
    @rsingler
    [​
    There are two versions (138kb & 400kb) of your great V57 calculator. Why two versions? Difference?

    Wow, 13 new versions still since my April download. Looking forward to seeing the refinements. Thanks for your ScubaBoard gift!!

    Best regards & happy diving!
     
  2. stepfen

    stepfen Barracuda

    # of Dives: 200 - 499
    Location: Greece
    478
    255
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    The 138kb version is for the "current" Excel version(s) that support xlsx files and the other is for the older versions (xls files) in case anyone is still using them.
     
    couv, Doctor Rig and rsingler like this.
  3. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,548
    4,039
    113
    With profound thanks (AGAIN!) to @stepfen, post #1 now has a revised version of the tool (v. 58) after his latest tank research.
    @stepfen has obtained data on an additional 40 metric tanks from Luxfer, ECS, Polaris and MES that are more commonly seen on the European side of the pond. The spreadsheet has been updated to include this info, and the manual revised slightly regarding the tank info provided. No changes have been made to any computational formulas, so current users who do not see or use these tank brands shouldn't feel compelled to download this "latest" version.

    Thanks again to the great ScubaBoard community for all your contributions!
     
    Jay, stepfen and couv like this.
  4. _Ralph

    _Ralph Manta Ray

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    Looks awesome!

    I’m one of those that rules of thumb and even the detail in this doesn’t work for me.

    But handy play around with to see what changes in equipment can result in changes in buoyancy!!

    _R
     
  5. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,548
    4,039
    113
    Hey @_Ralph , send me a PM with some of your data, and let's see if we can figure out why it's not accurate for you. If we can, and maybe fix a formula, that'll doubtless help others.
     
  6. gr8jab

    gr8jab Manta Ray

    # of Dives: 100 - 199
    Location: Oregon, USA
    629
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    First, thanks for doing this. It is an amazing spreadsheet.

    Just as a curiosity, could the 'Personal Buoyancy' be calculated from body weight and BMI (or fat/lean mass numbers) reported by some of the newer smart scales?
     
  7. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,548
    4,039
    113
    I think that's possible, but I'm not sure we have the right index. BMI alone as an index of "floatability" gets us astray, as we found out in the Air Force when huge muscular "sinkers" of heavy weight yet lean body mass, came back with high BMI numbers that obviously didn't mean "obese". Perhaps some sort of fat/lean index could be coupled with height and weight. After all, that's all that's going into your personal measurement of Personal Buoyancy in a swimming pool. It would be nice to automate that. I have some ideas, but have been hesitant to ask users to quantify their "fluffiness" so I could pin it down. :) For all readers of this thread, I would welcome a short confidential PM with your height, weight, self assessed "fluffiness" and your measured personal buoyancy. Perhaps if I graph that all out, something will become obvious.

    From some feedback, the Personal Buoyancy discussion isn't very intelligible in either the manual or the red comments in the "Diver and Dive" tab, so I'm working on making that more understandable, especially regarding what happens with the switch from salt to fresh water. Any suggestions you have on making that section better would be welcome.

    Thanks!
     
  8. gr8jab

    gr8jab Manta Ray

    # of Dives: 100 - 199
    Location: Oregon, USA
    629
    372
    63
    Well, I would definitely matter how the BMI was calculated. I think in your example BMI was figured from a height/weight table. That method assumes some typical dense body mass based on your height, and then any excess weight is considered all fat. If you're not typical, that method is totally inaccurate as you point out. I'm surprised anyone ever thought they were a good idea.

    The most accurate measure of BMI is hydrostatic weighing, but that's not really practical for most people. If a person can do that, they can certainly do the float test already described in the manual/spreadsheet.

    However, these new digital electronic bathroom scales measure BMI and fat percentages using conductivity and impedance. They are not super accurate, but when you average your daily readings over a period of time, it's pretty good. They are much better than using the lookup tables, and would not have misread your Air Force guy.

    Cheers :)
     
  9. gr8jab

    gr8jab Manta Ray

    # of Dives: 100 - 199
    Location: Oregon, USA
    629
    372
    63
    I was thinking about this too. Maybe the 'personal buoyancy input' should have it's own drop down box where we could tell if the test was done it salt or fresh water. Then you could calculate the missing information either way.

    The other drop down box would be for choosing where you will be diving, fresh or salt. That tells you which calculation to run (like it does now, I think).

    Hope I'm describing that OK.
     
    rsingler likes this.
  10. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,548
    4,039
    113
    Good suggestion. I'll work on it.
     

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