Bouyancy control while ascending - What are the best practices?

Discussion in 'New Divers and Those Considering Diving' started by 00wabbit, Jun 18, 2012.

  1. 00wabbit

    00wabbit New Member

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    Of all the things to worry about as a new diver I think bouyancy control while ascending is the one I am most worried about.

    On my first OW dive around 15-20ft I ended up on the surface without even realizing I was ascending. On another dive we were at about 40ft then slowly easing up to about 20ft. Because of reduced visibility in the quarry I didn't realize we were ascending. As we went up the air in my BCD inflated and I started moving up above the rest of the group. I realized what was happening and turned to kick down while dumping air. I managed to get back with the group without getting more than 5-6ft above them.

    MY worry is in a 45-55ft dive in the carribbean ascending straight up to a safety stop. Do you start dumping air immediately as you start ascending or do you do it as you need too, or do you try and predict and do it before you need too? I don't want to float away!

    Since the certification class I did get a computer (Cressi Leonardo) that can alert me when I ascend too quickly. I have had a little practice with it. According to my log on the computer I am still coming up too quickly at some point in the dive.

    I figure as I ascend I will have one hand on the BCD inflator and one hand on the computer to watch what's going on.
     
  2. vapourinthesea

    vapourinthesea New Member

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    Sounds like a good idea. Whether comp or gauges, keep an eye on you depth and deflate as need be. I use to have this problem as well...just watch your depth and try to start deflating before you need to. Also, when your buoyancy is perfect, then just your breathing car really help you stay where you want to be. Make sure your weighted properly too.
     
  3. Altamira

    Altamira Active Member

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    I tend to dump most, if not all of the air out of my bc as I start the ascent and then swim up. Also realize that if you are wearing a wetsuit, the compression will also decrease as you ascent and that will also make you more buoyant. I have always found it easier to add air if I need to stop the ascent than to try to get rid of it as it continues to expand during te ascent.
     
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  4. 00wabbit

    00wabbit New Member

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    This is what I was thinking. I did this on the last dive of OW certification and it seemed to work. I was able to control my speed up by kicking.
     
  5. MrsBBC

    MrsBBC New Member

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    Two other pointers

    A lot of newish divers think that they are effectively dumping air from the 'deflate' but often no air comes out the bcd, this is dependant on your trim in the water and how high the inflater is held. On the surface divers will say "but I was dumping air the whole time" and I have to explain to them that actually, they didn't dump any air.
    Past the 'point of no return' this is easy to remedy. If you are having trouble dumping air from the deflate, dry one of your pull dumps. If you are kicking down.... 'butt dump'!
    On your descent, dry dumping air in different trim positions so that you can recognise when the deflate will actually get rid of air and when it will be ineffective.



    Also, I am still surprised at how difficult it is to control an ascent when overweighted.
    The extra, unnecessary gas in the bcd expands and expands and expands. Get rid of it all before you ascend
    Try conducting another weight check on your next dive and see if you can lose a few lb

    Nic
     
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  6. freewillie

    freewillie Well-Known Member

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    If you are properly weighted then you should have minimal air in your BC. Regardless of depth, when you start to ascend you should dump most if not all your air. You should be in the habit of controlling buoyancy through your breathing while kicking to the surface. As my instructor said, "no elevators to the surface." in other words, you shouldn't be putting air in your BC to ascend then need to dump air as you go up.

    Also, the more shallow you are the greater the change in volume. At about 15-20 ft the air will expand quicker than you can respond. Before you know it you are ascending faster than you intended. The less air in you your BC the less likely this will happen.
     
  7. gcarter

    gcarter Surface Interval Member

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    During my deep course, on an 80 ft dive, we settled on the bottom and removed all air from our BCDs. We were then to kick upwards and see how far we got.

    Not so far. Mind, we were wearing 7+7, and I personally was wearing 24 lbs. Still - I would not dump all air.
     
  8. TSandM

    TSandM Missed and loved by many.

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    A tip I got from a fellow named jonnythan, here on ScubaBoard, was this: Start your ascent by inhaling and breathing shallowly with very full lungs. Go up a couple of feet and EXHALE. If you stop, inhale again and go up some more. If you don't stop, VENT. By never getting very far away from being neutral, you keep your rate of ascent relatively slow, and never outside the "window" that you can control with the volume of your lungs.

    You CAN get negative and swim up, but if you get distracted for any reason during that process and stop kicking, you will sink.

    Buoyancy control is breath control -- the more nervous you get about controlling your ascents, the less you will keep your breathing rhythmic and even, and the more buoyancy trouble you will have. Keep your breathing relaxed and controlled, and buoyancy will come with it!
     
  9. gcarter

    gcarter Surface Interval Member

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    If you are neutral, a few fin kicks should make you bouyant. Dump a few bubbles, kick, repeat. Watch the acent rate on your computer. If it goes faster than your kicking, you are not dumping enough, But don't dump it all.
     
  10. DivemasterDennis

    DivemasterDennis ScubaBoard Supporter ScubaBoard Supporter

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    Lots of good pointers so far. Of course, the first pointer is predive- to make sure you are properly and adequately weighted. Then here is my short list for buoyancy control on ascent, whether from 20 feet or 120 feet:


    1. Monitor your gauges constantly.
    2. Vent air from you BC as necessary.
    3. At 30 feet or so, (or at start of ascent if from 30 feet or less) if you have not yet dumped all your air, dump all your air
    4. At your safety stop depth (15-20 feet) add air if necessary in VERY SMALL increments to establish neutral buoyancy.
    5. After safety stop, vent all air from bc and slowly kick to surface.
    6. At the surface, inflate bc for positive buoyancy.
    With experience and practice, your breathing method- "top of the lungs," "bottom of lungs" - may kick in, and you will ultimately do ascents with total control through breathing and fine bc venting/adding with little or no kicking. We teach that in rescue class under the heading of "controlled buoyant ascent," and it's a pretty advanced skill, but one you can certainly master.
    DivemasterDennis
     
  11. Islandheart

    Islandheart Divemaster Candidate

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    While most and many of the suggestions above are good techniques to use during ascents, a few are less than safe.

    - Never breath in deeply, ascent a few feet and then exhale. This is beginning to teach breath holding and should be avoided. Skip breathing is also a no-no.
    *It only takes a few feet of over-expansion to cause DCI.

    - Never use, "adding air to a BCD to begin or during an Ascent" so that you are not kicking.
    As has been said, "Riding the BCD or using the BCD as an elevator", can lead to serious injuries and SHOULD NEVER be suggested or taught to beginners.

    Suggesting or "teaching" advanced techiniques to new/beginning divers, can and is hazardous. The "controlled buoyant ascent", is not a Skill in the Rescue Course. * If this is being "taught" in a Rescue class, it is outside of PADI standards and the Instructor/ DM should look at that and correct themselves.

    Hopefully Proper Weighting, for the End of the Dive;
    has been taught.

    Proper Ascent Positioning;
    Swim into a Feet Down, Head Up position. Left Hand holding the deflator up, with finger only on the deflator button (care should be given that fingers are not on the inflator button also) and the Depth gauage or computer in right hand in front of face so it can be monitiored..... then swimming up from a Neturally Buoyancy state, will keep you in control and safe.

    If you are not controling your ascent, read "kicking", and something else is causing your ascent, you're setting yourself up for trouble.

    Get control over your weighting before you dive (use a 500psi tank to check it at 15ft., get control over your total dive buoyancy by proper positioning and get control over your rate of ascent by how strongly you kick (ie you stop kicking and you should stop ascending).

    For your own sake, DO NOT RIDE THE BCD during an Ascent !

    my .02
     
  12. boulderjohn

    boulderjohn Administrator Staff Member

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    Interesting.

    Are you saying you don't teach students that they should control their buoyancy through the air in their lungs? What do you think of a beginning exercise like the fin pivot, in which students inhale, ascend a few feet, and then exhale? Do you teach that skill, or do you skip it because it is unsafe? How do you teach students to hover?
     
  13. 00wabbit

    00wabbit New Member

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    Thanks for all the advice. I get the jist of it.

    I like the idea of dumping all the air at 30ft just in case some is left over.

    I know I need to work on weighting. I am a big guy and I am pretty sure I was overweighted during the openwater dives. I could see how the bouyancy was harder to control. At 40ft I felt like I was putting in a lot of air to get neutral. Then as we slowly swam up the angled bottom towards 15-20 ft I started to elevate above the group and had to turn and kickdown while dumping air to slow my ascent.

    I am hoping to go back to the quarry with the instructor or a dive buddy next week to work on weighting and bouyancy control.
     
  14. SnorkelLA

    SnorkelLA Surface Interval Member

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    Keep your SPG, or whatever you use to monitor depth at chest level, dump all air, very lightly fin until the depth meter reads anywhere +/- 2 ft from 15, but try to stay as close as possible, this is only a SAFETY STOP we're talking about, not a full on staged decompression :) . Try to control your buoyancy using only your breath at this point, it will make it hella easier. From there, after the stop is done, simply "go on up!"
     
  15. boulderjohn

    boulderjohn Administrator Staff Member

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    I don't, and several people have already told you why.

    There are people who do advocate pretty much dumping all the air as soon as possible, even before starting the ascent. These are all people who have never done any cold water diving. You can do that if you are properly weighted in a thin wet suit, but if you are wearing a thick wet suit, that can be a disaster.

    In a thick wet suit, you are not properly weighted during the dive. Because the suit loses so much buoyancy under pressure, the amount of weight you need in shallow water is too much for deeper water. Thus, when you are diving at depth, you are overweighted and must use extra air in the BCD to compensate. If you dump all that extra air early, you may lose too much buoyancy and be unable to hold your depth.

    When I was a new instructor, I taught an AOW class with a young lady doing her first cold water dive in a 7mm wet suit and a hood. She was also the first person I had ever met who had been taught to dump all her air when she ascended, so I was surprised when she did that when we started our ascent. It took me 20 feet of rapid descent before I could catch her and stop her from plummeting into the depths.
     
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  16. DukeAMO

    DukeAMO New Member

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    I have a closely related question.

    I did my PPB classes with AL80s in two 5mm wetsuits, plus a hood, booties, and gloves, so I was wearing quite a bit of neoprene. I'm not a small person either (size L). I was able to descend with 24lbs of lead (slowly), and stay down through the dive and the safety stop at a depth of 15 ft. However, at a depth of about 5ft I got pulled up to the surface, even with an empty BC (and about 700 PSI in the tank). After that I wasn't able to descend again, so we swam back to shore at the surface. With 26lbs of lead, and 500PSI in the tank, I can exhale and slowly sink. So would the proper weighting for that configuration be 24lbs or 26lbs? In other words, is the goal to be able to hold a safety stop if you're already under water with 500 PSI, or is the goal to be able to descend again with 500 PSI? Is it worth carrying around the extra 2lbs of lead to avoid getting pulled up?

    We ended up using 26lbs, but I'm curious what others would have done. I will say, the dive with 24lbs was easier. Until the end.
     
  17. mala

    mala DIR Practitioner

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    there is about 6lbs of gas in an ali 80 that you will use during the dive.
    at the start of the dive you should be 6lbs heavy so that at the end of the dive you will be correctly weighted and able to stop at any depth.
    if your buddy needs help at the end of the dive its no good being stuck on the surface.


    2 x 5mm wetsuits?

    sounds like a drysuit was needed.
     
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  18. DukeAMO

    DukeAMO New Member

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    Hm, good point on being able to get back down if your buddy needs help. Why didn't I think of that?

    Drysuit - hah. Maybe someday.
     
  19. boulderjohn

    boulderjohn Administrator Staff Member

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    Diving with that much neoprene is always more difficult during the dive because you have to be overweighted at depth. Therefore, the less weight you have during the deep part of the dive, the better you will feel. In an ideal universe, you would hand off some of your weight once you were at depth and get it back when you ascend. Unfortunately, that isn't gong to happen. You therefore need to have enough weight to complete the dive--and I would say complete is with less than 500 PSI because you never know what might happen.

    That is one more reason to prefer a dry suit--constant buoyancy.
     
  20. chrpai

    chrpai New Member

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    Sounds like the PADI world. I perfer the horizontal trim position with my computer / depth gauge mounted on my right wrist and my hands free in the event that I need them. I also like making nuckle on nuckle contact with my buddy while maintaining eye contact and same depth. I only go verticle after the safety stop and only when I'm concerned about boat traffic.
     
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