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Buoyancy & Trim Drills

Discussion in 'General Scuba Diving' started by georgedavo, May 20, 2019.

  1. georgedavo

    georgedavo New Member

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    Hi All,

    I'm trying to work on my buoyancy and trim, and was just looking for a bunch of ideas for drills to try out at the local puddle.

    I'm pretty much at the point where holding a designated depth in trim with limited fin movement is OK, but as soon as you throw any other task in the mix I get a bit wobbly.

    Obviously general practice of valve shut downs, OOG drills, DSMB deployment is good to practice and will be practiced anyway, but was wondering if anyone had any nice little drills to mix it up.

    When I did Intro to Tech with Mark Powell at NDAC, he had me picking a lead weight up off the top of one of the containers, regain neutral buoyancy, descend to the floor of the container, regain neutral buoyancy, put the weight down on the floor, regain neutral buoyancy, and so on back up to the start position. I found this really useful.

    Cheers,

    George
     
  2. jb2cool

    jb2cool Moderator
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    The brick/lead game that you mention is useful, we sometimes do this when diving in quarries and come across our friend which is a concrete dog, he's fairly small but remarkably heavy, we pass him around the group adding/dumping gas accordingly.

    Other than that, pay around with going up and down. Go up to the surface in 1m increments and then go down again in 1m increments whilst remaining facing and within touching distance of your buddy/team.
     
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  3. Tel

    Tel Super Moderator
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    Do you have an old weight-belt with metal buckle?

    If so tuck a bit of the webbing end into you waist-belt so that the metal buckle is hanging down.
    Now go horizontal and go neutral so the buckle is just touching any horizontal surface like a rock, blockhouse , container etc.
    The buckle/belt can be felt when it touches and if the surface resonates the tap-tap of contact can even be heard.

    Makes keeping a set distance a doddle and once that's nailed throw in some skills.
    With a bit of practice can ditch the belt and repeat same skills :)

    It might sound a bit naff, but it's surprisingly effective.
     
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  4. georgedavo

    georgedavo New Member

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    Thanks for the responses, definitely things I'll try out!
     
  5. Tribal Chestnut

    Tribal Chestnut Well-Known Member
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    Empty pockets and clip contents onto DSMB line whilst at your stop depth.

    Fill up pockets again.

    Repeat ad nauseam.
     
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  6. Wibble

    Wibble Fish don't talk
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    Up and down is the main thing. Things are pretty easy at one level - spend ages at 6 metres waiting for the clock to count down. The challenge is changing depth. So even at 20 metres (or whatever your pond has), going up by a few metres and stabilising, then descending and stabilising is good practice. Ascent practice with an SMB is really good too.

    The only problem with going up and down all the time is your ears may block up.

    Definitely play with changing weight too.

    Good distraction practice is playing with a stage. Clip it on, unclip and move to the other side (if you've a RH clip!), passing to another person, pulling the hose out and putting it away... all with some reference of either another diver or something to look at as a datum. Throwing an SMB up is also good practice.

    It's amazing; the more you practice, the easier it becomes.
     
  7. Alex Denny

    Alex Denny Active Member

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    We were doing the 'move a shot weight' drill in Vobster at the weekend with 12kg and a large SMB as a lifting bag. I had the joy (as instructor) of swimming the weights out to where we wanted them, which involved getting me and the weight all neutrally buoyant - which is a great exercise as you have to think about buoyancy across your drysuit, wing and lift bag all at the same time.
     
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  8. Wibble

    Wibble Fish don't talk
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    Weight related quandary....

    Whilst diving this weekend (not in Scapa), got chatting to a guy with a single with BP and wing. A large wing. The diver commented that they couldn't use the small wing as they had to use so much weight to descend that "the small wing didn't have sufficient lift to get them back up again".

    Hmm.

    Thought for a few moments about pointing out that they're obviously grossly overweighted and they definitely don't need all that weight...

    Should one say anything?
     
  9. Dave Whitlow

    Dave Whitlow Super Moderator
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    Drysuit is for keeping you warm and the wing/bc is for balancing any excessing mass you are carrying (unused gas, bailout). The buoyancy required to support any load you are managing should be provided from an external souce, ideally a lift bag, enabling you to abandon the load should that be necessary.

    Being geographically wise I often gather scallops, sometime quite a lot. On scallop dives I use a single lift bag to support the scallop bag above the seabed. I gradually add gas to that bag as the harvest increases. When the gather is complete I send the bag to the surface, connected to my SMB, and I don't adjust my personal buoyancy in the process. Using personal buoyancy to balance any load might feel satisfying but it also is a trip to the edge of the incident pit and something I'd not do.
     
  10. Dave Whitlow

    Dave Whitlow Super Moderator
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    yes
     
  11. Wibble

    Wibble Fish don't talk
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    How would one approach giving such advice without lecturing?

    (BTW it was a 60lb wing, 40lbs was apparently insufficient!)
     
  12. Tel

    Tel Super Moderator
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    Not unless you want to get your hands dirty. .

    I'm reminded of a holiday trip where a diver was 'told' by another 'guest' that he was seriously over-weighted
    and despite him saying he was happy with the weight he had, peer pressure took over and he ditched a couple
    of lumps. On jumping in the diver struggled to keep down and when the tide turned out to be a bit stronger
    than anticipated, he was seriously struggling with the effort of fining to the point where he became exhausted
    very quickly, causing the entire group to abandon the dive on what now turned into what was in-effect a full on
    rescue.

    Sure some divers could do with advice, but unless it's matched with the solution and even an offer to help with
    the practical such, advice does have the potential to harm.

    In the incident above the advice was to drop some weight without a thought as to doing a buoyancy check.
    The logic that a diver who is over-weighted was clearly not familiar with a regular buoyancy check was lost to
    the diver giving advice.
     
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  13. Wibble

    Wibble Fish don't talk
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    Pretty much what I was thinking. If someone needs that kind of basic coaching, they'll need more than a simple explanation.

    Goodness knows how much lead there must have been to overwhelm a 40lb wing. Only time I've ever done that was pratting around with backmount and four stages (including one steel) in fresh water.

    As an aside, I do add a lot more weight (~3kg) in cold water as I want a lot more gas in my drysuit for warmth and especially on a deco stop.
     
  14. Tribal Chestnut

    Tribal Chestnut Well-Known Member
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    I wonder if reverting to suit for buoyancy might work better for you over winter?

    Ok, it might be anathema to you and against all that you stand for as you’re not doing it right as such, but managing a (perhaps) similar volume in your suit to that when you’ve added extra weight, but without also having to manage a large volume in the wing too, is little safer IMO.
     
  15. Wibble

    Wibble Fish don't talk
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    Definitely use suit for buoyancy in the cold. Can't remember what warm diving is like ;)
     
  16. Tribal Chestnut

    Tribal Chestnut Well-Known Member
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    I've booked a warm diving holiday in August. Can’t wait!
     
  17. Dave Whitlow

    Dave Whitlow Super Moderator
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    A seasonal change in diving techniques seems an odd concept. If extra warmth is needed then adding extra undersuit layers makes sense and that will require additional lead without any change in normal behaviour. Heated undersuit layers is another option.

    Merely adding excess weight is never a good answer as that requires excess gas in either suit or BC. Excess gas will make maintaining neutral buoyancy with changing depths more difficult, make controlling ascent and holding stops more difficult, and will result in higher gas usage. Excess gas in the suit is likely to migrate to whichever end is highest and might escape though the neck seal, or precipitate a feet first ascent. All these options are likely to cause loss of fabulousness and result in more tragic tales of woe being presented on here.
     
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  18. Wibble

    Wibble Fish don't talk
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    It's a little more nuanced than that.

    There are more layers -- and a heated vest -- which warrants more weight. Personally though I do prefer to have my drysuit more 'loose' when it's cold, especially on a stop where the cold works into your bones as you're stationary for a fair time. I'd much rather the gas in my suit on a stop than in my wing.

    Having a 'loose' drysuit doesn't mean one with great bubbles of gas, just that you have less squeeze. Dumping gas isn't a problem as one rolls to the right a bit and the shoulder dump does its job; flat trim distributes the gas evenly; socks and rockboots do their job of keeping the gas from one's feet; the membrane suit not having any intrinsic squeeze as with a neoprene drysuit.
     
    #18 Wibble, May 30, 2019
    Last edited: May 30, 2019
  19. Alex Denny

    Alex Denny Active Member

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    I don’t disagree with any of that particularly (though I personally use my drysuit for personal buoyancy during a dive, rather than my wing, unless carrying a lot of stages). However the exercise still involved balancing (and therefore adjusting) buoyancy across all gas spaces because I started with 12kg at the surface and had to swim them down to about 14m deep around a corner about 50m away. Of course, the lifting bag, my wing and suit all compress on the way down. To keep me neutral I need to manage my suit (or wing as preferred). To keep the shot weight neutral, I had to manage the lift bag - exactly per your comments. Honestly, it’s great practice.
     

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