Bouyancy control while ascending - What are the best practices?

[gcarter]

Why do you even care how I dive? I am comfortable with my style and it suits me. I just happen to like the minimalist style. If you have read the equipment list in my profile, then you know that I have some contemporary equipment that I use when necessary.

I honestly don't care what techniques you like to use. That is your choice. The OP was seeking knowledge and I merely offered my personal style as an option. Personally, I think your attitude needs a little work. What purpose is served by insulting someone you have never met simply because he or she does not share your ideas on diving style?

Besides, my post asking why one cannot swim up from 80 feet without air in a BC was not even directed to you. It was directed at gcarter.

I'll refer back to cuyler, post #38. I understand how you can do it using a changing weight scenario; it's pretty difficult to lift 20 or so lbs of dead weight off of the bottom without some air in the BCD. I am sure that there is the odd person out there who could do this, but I doubt there are very many divers who could, especially as a routine.

 

[farsidefan1]

I have no expertise whatsoever on cold water diving! (Thank the Lord) but I have done a lot of blue water ascents. No reference points, not near a wall etc. Just me, my buddy and the water. I GLUE my eyes on my depth guage while holding it so my buddy is in the background. It is amazingly easy for those not paying attention to drop quite quickly to dangerous depths while doing their 15 foot "safety stop" in clear water. I rarely have to make any adjustments but even so my eyes stay on the guage and my buddy. Nothing else matters.

 

[Flguy76]

I am a strong advocate of trying to stay ever so slightly negative and gently finning up on the ascent and maintaining a more or less vertical position. This is the best and safest and easiest way to learn bouyancy control on ascent. After the diver has mastered this, they can eventually do it with minimal (or zero really) swimming.

You don't dump air to begin an ascent and you don't add air either. You just take a few gentle kicks and start the ascent, vent air only as necessary.

As divers get better and better at maintaining trim and control they can begin to develop the ability to ascend in a horizontal position and ride a tiny bit of bouyancy up. However, to ascend in a horizontal position.. by definition you must be positively buoyant, and this is NOT the way to begin to teach people to ascend...

I myself generally stay vertical for ascent and can control the ascent by spreading my fins and breath control and use negligible upward kicking...

As a novice/newbie I keep hearing the term (as necessary) when referring to venting during an ascent. What I think a lot of experienced divers forget is (as necessary) means nothing to a beginner. When you say as necessary, in my understanding or lack there of it doesn't really clarify at which point that is? do you vent arbitrarily as you ascent every few feet or do you vent as you being to get too positive which sounds like a bad idea to me as you are already getting into a potentially unsafe situation. I would think one needs to vent before they get positive to maintain neutral or "slightly" neg. buoyancy. Can you clarify exactly what you mean by (as necessary) I referred back to my Padi manual to answer this question and low and behold it uses the exact same terminology (vent as necessary) but does not say when or how much to vent. During my cert class I was taught to just vent small amounts as I ascended, there was no specific instruction as to how much or when so that is what I have always done. Just random venting. we were also taught to ascend using an anchor line so a free ascent without something to grab onto was not covered in depth. Thanks.

 

[boulderjohn]

As a novice/newbie I keep hearing the term (as necessary) when referring to venting during an ascent. What I think a lot of experienced divers forget is (as necessary) means nothing to a beginner. When you say as necessary, in my understanding or lack there of it doesn't really clarify at which point that is? do you vent arbitrarily as you ascent every few feet or do you vent as you being to get too positive which sounds like a bad idea to me as you are already getting into a potentially unsafe situation. I would think one needs to vent before they get positive to maintain neutral or "slightly" neg. buoyancy. Can you clarify exactly what you mean by (as necessary) I referred back to my Padi manual to answer this question and low and behold it uses the exact same terminology (vent as necessary) but does not say when or how much to vent. During my cert class I was taught to just vent small amounts as I ascended, there was no specific instruction as to how much or when so that is what I have always done. Just random venting. we were also taught to ascend using an anchor line so a free ascent without something to grab onto was not covered in depth. Thanks.

You should be ascending slowly using your own physical power to make that happen. For most beginning divers, it is done vertically, with the feet below you providing the impetus through a swimming motion with the fins. As the air in the BCD expands, there will come a time when the BCD begins to pull you upward. When you feel that happening, dump a little air out so once again it is primarily your feet providing the impetus. Now, I am not talking about a really hard kick to continue going up. It should be a very gentle and easy swim. If it is hard, then you dumped too much air too soon.

As you become more adept at it and really fine tune your buoyancy, you will be able to do it without kicking. Many expert divers stay in horizontal swimming position as they ascend, using inhalation to initiate the ascent, and dumping air from the BCD a little at a time to control the rate of ascent.

It is a little like using the brakes to bring your ca to a halt. You use them as needed. It is impossible to put in writing how hard to brake as the car slows. It is something you learn by doing it.

 

[TSandM]

Flguy76, I'll give you the advice jonnythan here on SB gave me years ago. If, during your ascent, you exhale fully and you DO NOT STOP ascending, you need to vent. If you check this with each breath, an ascent will never get away from you.

To expand this, at any time during a dive, there is a "window" of depth variation that you can control by changing the volume in your lungs. As long as you are within that window, you can exhale to stop ascending, or inhale and breathe with fuller lungs to stop sinking. Once you are outside that window, you can no longer do it yourself -- you will have to add or vent air from your BC (or dry suit) to arrest your momentum. Obviously, when you are deep, that "window" is a bit wider, because the proportional pressure changes are small for any given change in depth. At 60 feet, I might be able to go up or down five or six feet and still stop myself with my breath; the same deviation from 15 feet is something I quite certainly can't control by breathing. That is why one has to be more vigilant about depth changes toward the end of the ascent, because that's when you want to go the slowest (according to decompression theory) but it's the easiest to lose control.

 

[Jeff Scott]

Thank you TSandM!!! I am constantly trying to play with my buoyancy and fine tune things...especially with using my lungs. I have heard time and again from the more experienced divers talking about how you should be able to stop your ascent or descent at will but I have never been able to achieve this jedi like control and I have often wondered what I have been doing wrong, But I must compliment you in that I have never had this explained to me any better than you just have. I can't wait to try this.

 

[00wabbit]

You guys just resurrected a zombie post I made last year after I first got certified.

It's funny how things change.

Now I understand the window of neutral bouyancy and I can feel when I am moving out of it. As I ascend I can feel my wing start to lift off my back slightly or my drysuit loosen a little. I can feel the pressure reducing in my sinuses a bit and I know I am moving up. I can tell when I need to vent and I am getting better at figuring out how much to vent so I don't over vent and go back negative.

The key just like all of you have said in the past is practice and good technique. I now try to make all my ascents and decents while in the horizontal position. Diving has become much more comfortable and my sac rate has gone up a lot by doing nothing more than getting comfortable.

 

[Jeff Scott]

The key just like all of you have said in the past is practice and good technique. I now try to make all my ascents and descents while in the horizontal position. Diving has become much more comfortable and my sac rate has gone up a lot by doing nothing more than getting comfortable.

Amen. I try to do all of my descents and ascents in the horizontal position and I'm pretty good at it but I still don't try to stray too far from a wall or the ascent line because I can't stop on a dime like how TSandM is talking about. It still fascinates me to watch my instructor do this with little more than an occasional fin flicker. In the deep diver course you have to do an ascent with only visual reference but I've only been able to accomplish this by staying slightly negative.

I'm happy that this thread got resurrected from this point on. I wish I would have found it a year ago...would have saved me a lot of frustration. Hopefully it won't take me too long to nail this. Thanks again TSandM.

 

[Skittl1321]

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.

Thanks for explaining this.
We were taught to vent all our air while we were ascending (but not to dump it before we started- but it was kind of stressed you shouldn't have air in your BC while ascending to the surface). I've never dove somewhere where rapid descent would be a problem (just crash into the bottom at 30-40 feet); but I see how it can be a real issue in a 7mm wetsuit. Never thought of that before.

 

[dumpsterDiver]

Thanks for explaining this.
We were taught to vent all our air while we were ascending (but not to dump it before we started- but it was kind of stressed you shouldn't have air in your BC while ascending to the surface). I've never dove somewhere where rapid descent would be a problem (just crash into the bottom at 30-40 feet); but I see how it can be a real issue in a 7mm wetsuit. Never thought of that before.

Assuming you are correct in your recollection of your training, your instructor is an absolute idiot! This is the kind of instruction that can cause people to kill themselves. They over exert on the ascent, breath like crazy, become panicked etc.. Just incredibly ignorant advice. Most likely it stems from the unwarranted fear of an uncontrolled ascent.

If instructors would only teach as TSM describes, very gently ascend and if when you exhale you are still rising, THEN dump a tiny bit of air from the BC.. Dumping all the air from the BC before the ascent, on a deep dive with a thick wetsuit.. is just incredibly stupid.. (Did I stress that enough?) It makes you wonder what other deficits exist within your training.