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Apparently hovering is physically impossible

Discussion in 'New Divers & Those Considering Diving' started by Javik, Sep 21, 2016.

  1. DevonDiver

    DevonDiver N/A

    # of Dives: 5,000 - ∞
    Location: Subic Bay, Philippines
    15,396
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    neutral buoyancy turtle trim scuba diving skills.jpg
     
  2. Kevrumbo

    Kevrumbo Banned

    # of Dives: 1,000 - 2,499
    Location: South Santa Monica Bay/Los Angeles California, USA
    5,659
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    More practical examples:
     
    Last edited: Sep 22, 2016
  3. Javik

    Javik Registered

    # of Dives: 50 - 99
    Location: United States
    67
    7
    Ah, I see, I had not considered that.

    This seems to suggest that trying to keep BC almost completely empty, and your lungs also almost completely empty and consciously breathing short in/out breaths, just enough to overcome the trachea/mouth "dead space / inaspirable air volume", will minimize the vertical position fluctuation.

    Large, slow, deep, long breaths are not helpful, and apparently should be avoided?


    Also, apparently any airspace contributes to making this harder, including air bubbles trapped in the foam of a neoprene wetsuit.

    A diver in tropical waters with just a skinsuit or a lycra swimsuit will probably have an easier time than an inland temperate lake diver that must wear 7-15 mm of neoprene all year 'round.


    Drysuit diving apparently makes this more difficult because of the air in the insulating undersuit, and really thick but easily compressed undersuits are also likely undesirable. (Whoops, time to sell off the Weezle Extreme?)

    The best drysuit undersuit may be the least compressible, to minimize volume changes even when squeezed, such as constructed completely with small individual rigid-wall foam hexagons like is used in some performance sport padding.
     
  4. Storker

    Storker ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 100 - 199
    Location: close to a Hell which occasionally freezes over
    17,202
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    Agree somewhat. Keep your BCD as empty as possible while being neutrally buoyant. In a heavy wetsuit at depth, you will need some air in your BCD to stay neutral. In a drysuit, you will need some air in your suit to avoid squeeze. No matter your exposure protection, at the beginning of your dive you will need some air in your BCD to compensate for the weight of your breathing gas.

    Strongly disagree. Shallow breathing may very easily lead to CO2 retention, and you really don't want any of that. Breathe calmly and normally in a regular rhythm, and fit your breathing rhythm to your slight variations in depth. It's not that difficult, but it may take a bit of conscious practice. Especially if you don't have an instructor or a competent mentor available.
     
    Captain Swoop likes this.
  5. CuzzA

    CuzzA Percoidea Wetwork for Hire ScubaBoard Supporter

    19,260
    33,607
    Scuba diving is more about gas than liquid. We are always consciously or subconsciously controlling, manipulating and monitoring the gases in and around our body. It's counterintuitive for many because we associate diving with water. For me, once I started to look at diving from the gas perspective everything started to come together very quickly.

    For example, you check the gas in your tank before diving. Equalize the gas in your ears. Adjust the gas in your BC. I don't dump a ton of gas to get negative anymore. Just enough to start my descent. During my descent I can tell when I'm picking up speed and becoming more negative and so I add a little gas the deeper I go. By the time I'm at my target depth I'm already pretty much neutral. Achieving the "hover" has more to do with trim and proper weighting than anything else. The volume of gas changing within my lungs only has very little impact on my depth, the bigger impact comes from the bubble of gas on my back. I'm to the point where I don't dive with any lead unless I'm in a suit greater than 3 mil. This is because I dive steel or neutrally buoyant aluminum tanks.

    Regardless where the weight is, for every pound you are over weight, that is a pound that must be compensated for by the gas in your BC. The bigger the bubble, the more difficult it is to control. Changes in depth are amplified with the larger volume of gas expanding on your back. I breath essentially normal when diving (slightly deeper breaths and full exhales to eliminate CO2) or when trying to maintain a static depth. If I want to raise up over a ledge or some obstacle I'll take a large breath. Maybe even hold it for a second because the buoyancy change is often delayed. When I feel I'm rising, I'll begin to exhale. I'll do the opposite for trying to descend a little. I do not like shallow breathing. CO2 headaches are unpleasant after a dive.

    As noted, much of this comes from either extensive instruction or experience. Dive more. Dive as often as you can. Keep making adjustments and before you know it you'll be properly weighted and can hover essentially motionless and use your lungs to help you dive. But, remember, diving is all about gas, not liquid. :)
     
  6. CuzzA

    CuzzA Percoidea Wetwork for Hire ScubaBoard Supporter

    19,260
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    ...Although, it does appear "Mr. Neutrally Buoyant Turtle" is kicking up some silt there... Who taught this guy to dive? Geeze.
     
  7. wspalding

    wspalding Contributor

    # of Dives: 100 - 199
    Location: Grafton, MA
    252
    106
    I agree with CuzzA comments. I weight myself so that I am just slightly negative when I exhale at the surface with no air in my BC. Once I've descended several feet I'll generally invert and fin down to the reef rather than freefall. As I approach the reef, a couple minor bumps on the inflator hose is enough to control my descent and allow me to get neutral. With the exception of diving a large ledge where my depth can vary 15-20 feet, I'll rely on breath control (never shallow breaths) to control my position, and I rarely make adjustments with my BC. Much of this was taught in my OW classes, and I disagree that buoyancy control and hovering are not properly taught, but it does take practice and experience to become proficient.
     
  8. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
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    yes and no.

    you want to breathe "normally" i.e. if you are not moving, you should have a tidal volume no more than if you are sitting on your couch at home. If you are casually moving around, you should breathe no more than you do while walking to the kitchen to grab a beer. Same frequency, same breath size.

    The smaller the breath, the smaller the depth change, but again, it isn't going to be a huge delta unless you take a big breath in, hold it for a while, then exhale it all out, and hold it a while. If you breathe normally the mass of your body and the rig, combined with the drag created by a flat profile is going to make the acceleration so slow that you aren't going to experience much of a depth change at all.

    Yes, bathing suits, skins, etc will not contribute to buoyancy change because they don't have air space, and thick wetsuits will. The direct contribution of the wetsuit is fairly small, but the fact that you have to offset the total air space in your wing is going to cause a fairly rapid acceleration of buoyancy change in shallower depths if you aren't careful to dump as you change in the water column. This is not something that you should be fighting actively though, only when making conscious depth changes. I.e. I can hover in a 7mm farmer john in the 3ft deep section of a pool with 0 problems where I have roughly 4-6 inches above my feet, and 4-6" below my chest. I reiterate from various posts I've made over the years, if you can hover in the shallow section of a pool reliably, you can hover anywhere.
     
    RyanT and CuzzA like this.
  9. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Boulder, CO
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    No, you just needed to start with a different instructor.

    Buoyancy and trim are required components of the OW course. It is the instructor's job to teach you how to do it.

    Many instructors firmly believe that the only way to teach basic diving skills is to plant students firmly on their knees on the bottom of the pool or OW diving site while thoroughly overweighted. PADI recommends against teaching skills on the knees now, and students are by standards supposed to be properly weighted in the pool and in the OW. If you are properly weighted, you cannot do the skills planted on the knees, so instructors who insist on teaching that way have to ignore that proper weighting standard.

    A number of years ago I met a young woman who told me the sad story of her certification in a now defunct Sport Chalet in southern California. The instructor's philosophy in the pool was to give everyone 20% of their body weight in lead so that they could stay firmly planted on the bottom. This 100 pound woman wore 20 pounds, an absurd amount of weight. Each pound overweighted requires nearly a pint of air to compensate, so i would guess she had to overcome the expansion and contraction of more than 2 gallons of air in the BCD in order to achieve and maintain neutral buoyancy. I told her I did not see how she could do the buoyancy exercises, including hovering, with that much lead. She said she could not do the hover at all, and neither could anyone else in the class. The instructor said that hovering and neutral buoyancy were advanced skills and were not required in the OW class. .

    That instructor was lying, though. It is required, and all it takes is an instructor willing to do it.
     
    RyanT and Lorenzoid like this.
  10. ScubaInChicago

    ScubaInChicago Professional Photographer

    # of Dives: 50 - 99
    Location: Chicago, IL
    1,561
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    The OP should take a GUE Fundamentals course to help find that sweet spot.
     

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