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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
    4,510
    5,636
    113
  2. Turtle Friend

    Turtle Friend Angel Fish

    # of Dives: 50 - 99
    Location: Beijing
    8
    1
    3
    Hi Scubaboard,

    I (186 cm, 86 kg) calculated a couple of scenarios according to my current (warm, salt water diving in 3/5mm and -0.9 kg aluminium BP/W, -1.8kg first stage, currently 3 kg of lead) and my future dives (cold, fresh water diving in drysuit with -1.5kg canister light, -1.8kg first stage and steel -2.7 kg BP/W). Seems like I need for the warm, salt water dives 30lb/14kg and for cold, fresh water dives 40lb/18kg. However, after reading some threads I didnt find any answer to my newbie-question: Why shall I simply not choose a Wing with a very high Wing lift (40 lb) to be prepared for any of the 2 above scenario? That I have a wing with a high lift capacity does not mean that I will use all the capacity whenever I don't need it (e.g. warm, salt water diving in 3 or 5mm). Right?

    Additionally I need to fine tune my personal buoyancy: Thus, I would like to know whether I can do the personal buoyancy test in chlorinated water (like a swimming pool) and mark that in the sheet as fresh water or will that difference (fresh vs. chlorinated water) affect the results significantly?

    Thanks for answerring my question
     
  3. stepfen

    stepfen ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Greece
    650
    447
    63
    Hello and welcome.
    The problem with having a wing with "very high lift capacity" as you call it is that high lift comes with the price of more wing material hence more bulk and more drag in the water (even when the wing is empty). That being said I wouldn't call a 40lb wing "very high lift capacity". My figures are somewhat similar with yours (I am close to 105kg and 190cm and BTW you don't mention anything about what tanks you dive - tanks can make a huge difference, I use 15lt steel tanks) and I dive with a 17lt wings (which should be close to 40lb - sorry I live in the metric world). 15lt wings are usually considered "standard" here and when you put them side by side with mine you can hardly notice any difference in terms of dimensions. There are wings, used for example for big double tanks, that have lift of close to 22lt/60lb or more. That's what I would call "very high lift" and if you don't need such lift you should stay away from them.

    In your case I would get a 17kg wing to cover both summer and winter. If you have the $$ you could buy 2 wings (and maybe a second heavier steel plate for winter - just saying :) ) but that's up to you to decide.
    BTW try to spend a lot of time with the tool to make sure you are using it correctly, with correct numbers and that you haven't missed any details. Small changes or mistakes can make quite a difference in the results. Also after you get the results you should try to verify them in the water. Differences of +/- a couple of kg can occur.

    The difference between chlorinated and really fresh water should be negligible. Remember all these are approximations anyway.

    All the best
     
    rsingler likes this.
  4. Turtle Friend

    Turtle Friend Angel Fish

    # of Dives: 50 - 99
    Location: Beijing
    8
    1
    3
    Thanks for your answer. My categorization that 40 lb lift capacity was very high was due to the fact that I have never dived doubles so far (but want in future/will) and in this case I understand that 40 lbs is at the higher end of single tank lift capacity (at least what I can find on manufacturers websites like Halcyon for single tank wings).
    Currently I don't have my own tanks so I mostly dive rented Generic AL80 (first row in the calculator).

    I was thinking to get a 40 lb (18kg) wing and a steel backplate (2.7 kg) and a 30 lb (14 kg) wing an aluminium backplate (0.9 kg). I hope that would be fine.
     
  5. Jcp2

    Jcp2 Literally virtually diving ScubaBoard Supporter

    1,049
    1,048
    113
    Maybe that’s a high lift figure for a wing, but most divers use a jacket, and that amount of lift is fairly typical.
     
  6. Sbiriguda

    Sbiriguda Manta Ray

    # of Dives: 25 - 49
    Location: Italy
    971
    189
    43
    Awesome thread , thanks
     
  7. jnocerin

    jnocerin Angel Fish

    # of Dives: 0 - 24
    Location: San Jose, CA, United States
    14
    8
    3
    First off this tool and all of the updates made through diver input is fantastic. So I am a relatively new diver, not by years, but by number of dives (currently I have 12 dives). I am preparing to start diving more regularly since moving to NorCal, and just got an aqualung semi dry solafx 7/8mm How would I correctly account for that I. The wetsuit tab as it seems to be more buoyant on the surface, and I am fully floaty with just the suit. For reference I am 5”8”, 220.
    I plan to figure out my buoyancy in my pool soon, but it currently too cold (unheated) to determine my base personal buoyancy, although I know I can easily stay on the surface taking normal breaths on my back, so I assumed “neutral” 0 in the spreadsheet for now.
    Thanks in advance, and excuse the Newbie level of the question.
     
  8. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    4,510
    5,636
    113
    No worries!
    I dive the exact same wetsuit here in NorCal. Great neoprene!
    I enter as wetsuit, 7.5mm, New_Soft
    to account for the average between the chest and leg thicknesses.

    As for your personal buoyancy, from what you describe in a presumably freshwater pool, I might be tempted to put in +4# for salt water rather than zero, but that's only a WAG.

    Feel free to open a conversation with me as you work the tool. Thanks for joining the discussion!
     
  9. David Novo

    David Novo DIR Practitioner

    # of Dives: 100 - 199
    Location: Porto, Portugal, Europe
    345
    112
    43
    Is there an option to account for water salinity? For example the one of the Atlantic Ocean vs Red Sea is very different, with very different impact on buoyancy.
     
  10. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    4,510
    5,636
    113
    At this time, there is not. The default value is an average salinity, which apart from the Red Sea, won't mean more than a 1.5 lb inaccuracy.

    If you're interested, PM me and I'll tell you how to enter the exact value inside the tool for the salinity you wish to use.

    If there's enough interest, we can certainly add that as an option.
     
    David Novo likes this.

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