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To weight or not to weight

Discussion in 'New Divers and Those Considering Diving' started by BettyRubble, Jul 21, 2009.

  1. simonru

    simonru Master Instructor

    # of Dives: 200 - 499
    Location: Kenya
    54
    5
    8
    I've been instructing a few years now... and we try to get the weighting right first time in the pool:- here are a few issues we come across
    1. People get anxious about sinking so they super fill their lungs. We try to get them to relax
    2. People complain... "I can't sink!" yet they are flapping their feet. We try to get them to relax
    3. When at the surface, doing the buoyancy check, people who's weight we've thought we got about right, when they practice find that they're usually a kg or so over weighted. We tell them to remove a weight, and get them to relax.

    I was super weighted to get me to sink in my open water. 3mm shortie with 10kgs of weight according to my log book. Fortunately an instructor at another school was able to advise me and I halved that over night. Now in a 3mm long suit I can get away with 3kg (steel tanks). Although I got quite a shock on a visit to the Red Sea, with a 6.5mm semidry and aluminium tanks!

    I think generally as new divers we have to practice... and see if we can drop some weight at the end of a dive. Oh yer. and relax
     
    Peter69_56 and waggs like this.
  2. augurs

    augurs DIR Practitioner

    # of Dives: 25 - 49
    Location: Bay Area, CA
    22
    3
    0
    I'm extremely buoyant even without a wetsuit to the point where I don't even need to move at all to stay at surface even when vertical. That led to my instructor telling me that I didn't need to tread for 10 minutes because she had seen enough.

    But anyway, I've been diving heaps recently all in similar conditions and same gear. When I started out, I needed 7 kg in salt water with a 3mm shorty and AL80 but sometimes the second dive I'd go down to 6 kg. But my last few dives I needed 8 kg to maintain my buoyancy! I'm told that my buoyancy and trim is pretty good for the number of dives I've done when I feel properly weighted.

    Still on vacation so I don't have a scale but I tend to be around 150 pounds but fairly sure I lost a bit weight and built up some muscle from all of the diving I've done recently. I'm a 5'5 female. Even when I was in awesome shape and tinier, I was still very buoyant.

    Why would my weight requirements change so much in a short time? This has been over 3 weeks or so.
     
  3. Peter69_56

    Peter69_56 Divemaster

    # of Dives: 500 - 999
    Location: Warragul Australia
    1,528
    616
    113
    For many divers, particularly new divers, the buoyancy issue is more that they are a little nervous and thus tend to hold partial lung full of air by breathing very shallow, in particular at the start of the dive. Once they get down, they then relax more and breath properly emptying their lungs more on exhaling. Then they feel heavy the whole dive thus dropping weight on the next dive. But due to their ongoing nervousness, they retain a fair amount of air in their lungs when trying to submerge next time and float, thus reinforcing their thought that they need massive amounts of weight.

    When I am trying to weight up some new gear, I ensure when I am doing the checks at the start, and more importantly at the end of the dive with empty cylinders (30 BAR) I exhale fully and wait a few seconds to see if I float or sink (with a fully empty BCD/wing/drysuit). If I float then slightly more weight and try again, if I sink, lose some weight and check again.

    Once you establish your weight component then you can sort trim by shifting weight about.

    For me the big trick is to do all this at the end of the dive with 30 BAR (in particular when using an aluminium cylinder) and fully emptying the BCD and lungs and waiting a few seconds to see the result. In this way, with recreational divers using aluminium cylinder, BCD, once you have done this and feel confident about it, the start of the dive is a breeze as you will always be a bit heaver due to the additional air weight and thus "must" sink with an empty BCD on exhaling.
     
  4. augurs

    augurs DIR Practitioner

    # of Dives: 25 - 49
    Location: Bay Area, CA
    22
    3
    0
    I don't add air to my BC underwater either, I'm not sure if that's a good or bad thing. I've heard both but my buoyancy seems good. I can't dive again for a bit but when I hovered, I only had to move my fins a little side-to-side so the current won't sweep me away.

    I can descend without too much issue at the start of my dives and my air usage is pretty good according to the divemasters I've dove with. I tend to keep my lungs on the fuller side with short exhales which is how I breathe up on the surface too. I think this may be why I need a bit more weight than usual but I tried to not keep my lungs full most of the time and it wasn't comfortable for me.
     
  5. Peter69_56

    Peter69_56 Divemaster

    # of Dives: 500 - 999
    Location: Warragul Australia
    1,528
    616
    113
    Keeping your lungs full and then shallow breathing is not a good way to approach diving. It has a tendency to keep CO2 in your lungs as you are not fully exhausting it thus making you feel you are out of breath. The more shallow you breath the greater the feeling. If you feel this way under water, being calm and deep breathing with full exhaling will stop the feeling.

    An example of this is to get a long tube (say conduit of 1-2 inch diameter about 3-4 foot long. Then only breath through the tube for say 5 min. You will find that you feel out of breath. The cause is that although you are exhaling, part of the exhaled gas (containing high C02) remains in the tube and your lungs, over time you get more CO2 and less oxygen, causing the "short of breath" feeling (which is what high C02 does). If you then remove the tube and deep breath and fully exhaust a number of times, this feeling goes away.

    Also I agree totally, new (and nervous) divers often breath shallow and don't exhale properly, and also often are unconsciously finning when trying to descend. I guess it may be a natural reaction to being in water and unconsciously trying to tread water. The combination of these two things on the surface makes a diver remain buoyant, thus they often add weight unnecessarily and then become heavy once under the water and relaxed.

    As previous posters have said, relax, relax, relax, breath out on descending and don't fin (after all you are trying to sink, not float).

    Have fun diving.
     
    Last edited: Nov 27, 2013
  6. simonru

    simonru Master Instructor

    # of Dives: 200 - 499
    Location: Kenya
    54
    5
    8
    Just a point of order. She NEEDS to see 10 minutes. 9:59 is not "seeing enough".
    If she didn't get a 10 minute float she has broken a standard and would need to have her wrist slapped.
    Just saying.
    ;-)
     
  7. sibermike7

    sibermike7 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I just don't log dives
    Location: Tallinn, Estonia
    1,158
    115
    63
    Hear!! Hear!!
     
  8. PhatD1ver

    PhatD1ver ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Shanghai, China
    334
    141
    43
    I guess I am going to toss in a lesson learned during my OW qual... Actually, I had finished all my OW dives the first day of the trip I made to Thailand (return trip following DSD dive and three others a few months before)... on the second day, we go out for three more dives, and during dive 1, I'm feeling like I'm the guy on the bottom of the wheelbarrow race. I'm neutrally buoyant, but I'm swimming 'downhill' and it gets progressively worse as I go, and I'm letting air out of my BCD periodically even though we started at 20m and only went to 15m...

    After dive 2, I'm pooped diving and swimming against current like this, I'm thinking I've done something wrong... until after the surface interval... I had a nagging suspicion that my inflator hose had a small air leak... so I told my instructor and we made sure to dump all the air (and water) out of the BDC during our 1 hour SI and left the tank valve on and the BCD connected... guess what? we returned to find the BCD partially inflated...

    What was happening (due to my size) was that as it slowly took on air under water, the air was trapped in the lower end of the BCD when I was swimming level, and would hold my legs up, so I was swimming downhill and it was kind of behind me, so I didn't notice it unless I 'sat up' in the water and the air then rushed to the shoulders of my BCD (and made me ascend a little)...

    Being as it was a rented BCD, there wasn't anything we could do (only one that size), but I got a lot of practice bleeding a little air out every few minutes.. the BCD has since been repaired,

    Lesson here is, make sure your equipment is working right too, or all your effort in becoming trimmed and neutrally buoyant won't mean squat.
     
  9. Arwen

    Arwen Angel Fish

    # of Dives: 25 - 49
    Location: Lithuania
    36
    6
    8
    Now I don't know anymore what ir proper weighting. I am a female, 164 cm, 62 kg. I was diving in red sea with a 3 mm short suit. I've finished my OW with 8 kg of lead. This year I decided I was overweighted and lost half of that weight - started with 7 kg and after several dives only used 4 kg. With 4 kg I can easily sink. Sometimes I think I could do that without any weight on my belt. When 70 bar is left sometimes I feel a slight tendency to go up if I am not controlling my breathing, but there wasn't a time that I couldn't make a safety stop or something.
    But in some other thread of SB I read that people prefer to stay slightly negative with 50 bar. So now I am confussed...
    According to The Book I should be neutral at 5 m with 50 bar.
    With those 4 kg it all depends on my mood - if I am relaxed keeping safety stop is easy, if I get a bit stressed (for egzample I hate the sound of boats engine) I nhave a tendency to float up which I fight with exhaling strong and start bouncing a bit.
    Is it proper weighting or do I need more lead?
     
  10. simonru

    simonru Master Instructor

    # of Dives: 200 - 499
    Location: Kenya
    54
    5
    8
    Sounds like you're about right. Many people are over weighted on ow. I was. Not good practice. Just learn to relax when you hear boat noises☺ or see a whale shark.. Relax, dump with raised left shoulder..(there's probably a bit more air in your BC). The more you dive to more weight you'll drop. I can manage with 2kg 3mm shortie in salt water(need a bit more for red sea) and I'm just under twice your weight (women tend to be a not more buoyant) but that's with 12l steel tank.
     

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