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Thread: Sink-y feet

  1. #41
    Established TDF Member JimmE's Avatar
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    Quote Originally Posted by nigel hewitt View Post
    To match the TDF vibe : I bought a rebreather, well my fourth.

    One of the first things I did was get it in the pool in all the kit, yes gloves and hood, and in the shallow end (so I can reach my pile of weights on the bottom) I trimmed it for neutral buoyancy with weights in pockets et al.
    Then I carefully put everything in the right pouches except for 2 x 2Kgs which I held in my hands.
    Then I just hung in deeper mid water and moved my hands from my waist to sticking out in front of me until I found the 'trim' spot.
    Trim is balanced so where you put yourself there you stay.
    I noted the exact position of my hands and worked out the 'moment' it applied (weight * distance from my waist as roughly the balance point)
    Then I worked out how much weight that was as some convenient point to actually attach it. Remember I am just moving weight now not adding or subtracting.
    I fixed it there and went back in the pool. Perfect.
    Camera nose down in a hole, upright or classical 'flat' deco position. It just works.
    I actually look competent which is a mean con trick as I'm not.

    Physics is fun
    Heh, perhaps not quite to the same extent but I think my next pool session will be similar as I've had to switch around a fair bit of kit this year now in prep for fundies. Dives last weekend were much more comfortable than those at NDAC in Jan and Feb but I'm still not as comfortable/stable as I was in my old setup.

    The club were already laughing at me for my 'full weight check' with a single 15 on a single tank wing in the pool in January - complete with drysuit/arctics/hood/gloves/umbilical torch...




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  2. #42
    Established TDF Member nigel hewitt's Avatar
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    Quote Originally Posted by JimmE View Post
    The club were already laughing at me for my 'full weight check' with a single 15 on a single tank wing in the pool in January - complete with drysuit/arctics/hood/gloves/umbilical torch...
    Physicists doing silly things episode 5:

    I tied my 5mm Hydrotech gloves and my 5mm Otter hood up in a bundle with a lead belt weight (about 1.75Kg) and dangled them in the water butt.
    Out of the water they weighed 2.11Kgs and in fresh water 0.61Kgs so 1.5Kgs of buoyancy which is, I confess, quite a bit more than I expected.
    (OK 150 grams of that is the lead 'floating'.)

    You have to have the full kit. I put the hood on but pull it down round my neck and the gloves are taped to my wrists.
    The undersuit just means it's 'boil in the bag' diver time.
    Helium, because I'm worth it.
    Waterboarding at Guantanamo Bay sounded like a radical holiday opportunity until I looked it up.

  3. #43
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    Quote Originally Posted by nigel hewitt View Post
    Physicists doing silly things episode 5:

    I tied my 5mm Hydrotech gloves and my 5mm Otter hood up in a bundle with a lead belt weight (about 1.75Kg) and dangled them in the water butt.
    Out of the water they weighed 2.11Kgs and in fresh water 0.61Kgs so 1.5Kgs of buoyancy which is, I confess, quite a bit more than I expected.
    (OK 150 grams of that is the lead 'floating'.)
    Yeah that's a bit more than I'd've estimated

  4. #44
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    Quote Originally Posted by nigel hewitt View Post
    Physicists doing silly things episode 5:

    I tied my 5mm Hydrotech gloves and my 5mm Otter hood up in a bundle with a lead belt weight (about 1.75Kg) and dangled them in the water butt.
    Out of the water they weighed 2.11Kgs and in fresh water 0.61Kgs so 1.5Kgs of buoyancy which is, I confess, quite a bit more than I expected.
    (OK 150 grams of that is the lead 'floating'.)

    You have to have the full kit. I put the hood on but pull it down round my neck and the gloves are taped to my wrists.
    The undersuit just means it's 'boil in the bag' diver time.
    Physics is fine - but don't ignore biology ... i.e. what happens when you move your body (stretch your arms or legs for some reason), adjust body tension, or you actually use your bailout / have to rotate cylinders?

  5. #45
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    Quote Originally Posted by graham_hk View Post
    or you actually use your bailout ...
    Total pain in the arse... with an empty steel 10 that's light as fk on one side and an al80 full of 50% on the other I end up with a right fight on my hands. I just tried this as an "I wonder" but it's a proper ball ache. I'm quite happy to manage an ascent like that but it's not helpful. It would be the same pain in the arse until you'd breathed the first 40 bar or so of 50%.

    How do you mitigate for this sort of thing? Is there a trick I'm missing?

  6. #46
    Established WTF Member Spirit of Guernsey's Avatar
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    Quote Originally Posted by WFO View Post
    Total pain in the arse...
    How do you mitigate for this sort of thing? Is there a trick I'm missing?
    Put both stages on one side.
    There are four varieties in society: the lovers, the ambitious, observers and fools. The fools are the happiest.
    Hippolyte Taine French critic and historian (1828-93)

  7. #47
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    Quote Originally Posted by WFO View Post
    Total pain in the arse... with an empty steel 10 that's light as fk on one side and an al80 full of 50% on the other I end up with a right fight on my hands. I just tried this as an "I wonder" but it's a proper ball ache. I'm quite happy to manage an ascent like that but it's not helpful. It would be the same pain in the arse until you'd breathed the first 40 bar or so of 50%.

    How do you mitigate for this sort of thing? Is there a trick I'm missing?
    You have to use your body to compensate for changes in equipment...


 
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