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Thread: Bouyancy control while ascending - What are the best practices?

 


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    Bouyancy control while ascending - What are the best practices?

    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.

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    vapourinthesea's Avatar
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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.

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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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    Quote Originally Posted by Altamira View Post
    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.
    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.

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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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    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.

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    Quote Originally Posted by Altamira View Post
    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.
    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.
    "Boys need to get together and do boy things with other boys occasionally. I'm okay with that." My Wife.

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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!
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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.
    "Boys need to get together and do boy things with other boys occasionally. I'm okay with that." My Wife.

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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

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