Ascending without BC's deflation / inflation

[Thalassamania]

I would not try to teach or practice an air siphon in a pool, too shallow, things change too fast for initial learning.

 

[dumpsterDiver]

"Ascending with your lungs" means varying the volume around which you are cycling your breathing. You can breathe "at the top of your lungs", which means with your lungs almost full, taking small breaths in and out, so the average volume in your lungs is very large. Or you can breathe from the "bottom of your lungs", with the lungs almost empty, cycling your breathing around a much smaller volume point. Neither is efficient breathing, and it's not what you want to do throughout your dive -- that's why you HAVE a buoyancy compensator. At the beginning of the dive, you adjust your BC to compensate for the gas you intend to use, and any compression of your exposure protection. Then, as the dive goes on and you work your way shallower, you slowly bleed gas out of the BC to retain neutral buoyancy. During this time, if you need to go up or down small amounts, you can do that with breath control -- but if you remain at a different depth, you adjust the BC, rather than continuing to breathe in an artificial manner.

For ascent, you inhale and begin to cycle around a large lung volume. As you begin to rise, you can exhale more, or exhale sharply to stop your ascent. If exhaling doesn't stop you, you vent your BC and bring your system back to neutral.

If you run out of air in the BC (and dry suit, if you are using one) before you get to your safety stop, you were underweighted. And some of us weight ourselves so that we will never have an empty BC until we get to the surface.

If, for some reason, you are unable to retain air in your BC, you should be able to swim your rig up. I don't like doing routine ascents that way, though, because if you get distracted during the ascent and forget to keep kicking, you will sink, and you must always be titrating the amount of kicking to keep your depth or your desired ascent rate. I find a neutral ascent is much more of a lazy man's ascent -- by being near neutral all the time, it's extremely easy to stop, either for decompression, or to deal with a problem or even just watch something interesting.

I thought all of this was VERY good advice, up until the end. I've found that for new divers that are performing an ascent in open water with no visual reference and nothing to hold on to, it is best that they try to stay just ever so slightly negative on the ascent. If they accidentally get too bouyant they stop kicking (and of course exhale as you mentioned) and this should take care of it. That is what I taught.

The goal is to try to keep the new diver on the negative side of the knife edge of bouyancy control. I am talking maybe 1-2 lbs negative, maximum.

However, as a diver progresses, they can play games and try to be less and less negative for the ascent.. until eventually they can ascend with essentially no movement or kicking, just breath control and precise use of the BC. However, FIRST the diver needs to be able to manage a slightly negative ascent, before a perfectly neutral one.

 

[crogue]

On a personal note, without getting into any of the "issues" involved. I stopped using my bc about 400 dives ago and completely removed my air cell about 90 dives ago and love it.

 

[Den7]

Neat! That's a fantastic advice! It looks like I will have an entire list of things to try and practice during my next dive.

Could you please, comment on my remark highlighted below in red?

Another thing to try in the pool. I know I kind of hijacked the thread, but learned alot and am going to play with both these options. I don't necessarily think the negative assent is an improper way to teach students, and see some advantages in that method, but I also like some of the advantages of the other methods.

Quote:
Originally Posted by Thalassamania
This seems a good place to (once again) mention the "air siphon," something I have discussed before. Each BC is a little different so you will need to experiment and practice if you want this in your bag of tricks. It can result in a highly controllable ascent, kinda the best of both worlds:

Start kicking up. When your BC has expanded enough to keep you moving, relax and let it carry you upward. Isn't it the place where after some time you would have your computer's alarm go off for violating your ascend rate? Hold the oral inflator hose as far down (deep) as you are able and keep the oral inflation button OPEN. Continue to keep the oral inflator button open and move the hose up until air starts to trickle out of the oral inflation mouthpiece, then lower it till it just stops. You now have an air siphon from your BC or BP/W that you can use to control your ascent or descent rate with amazing precision. Just remember to keep the oral inflator OPEN ALL THE TIME. THIS TECHNIQUE REQUIRES PRACTICE - try it on some normal ascents first!

Another thing to try in the pool. I know I kind of hijacked the thread, but learned alot and am going to play with both these options. I don't necessarily think the negative assent is an improper way to teach students, and see some advantages in that method, but I also like some of the advantages of the other methods.

 

[Den7]

I use just enough weight so that I will be neutral when my tank is at 500psi. I have a very small amount of air when doing my 20 foot hang, then dump it all and make a very slow swimming ascent. I'm only a pound or so heavy at this point, since I usually have about 1000 psi left.

I can always add a shot of air if I need it. Otherwise I just wait until the surface to re-inflate.

Are you able to control your bouyancy from the moment you dump it all till the second you make it to the surface by simply swimming?

Is there anything wrong in doing it this way? Could any experts comment, please?

 

[fire_diver]

On a personal note, without getting into any of the "issues" involved. I stopped using my bc about 400 dives ago and completely removed my air cell about 90 dives ago and love it.

You're in Stillwater? I live in Enid. We need to dive together. I'm in awe of divers who can dive without a BC or with no air in thier BC. I watched our DM do that in Cozumel. From 100 feet to the surface, I dont think I ever saw air in his BC. And, his bouyancy was great. I think this is the next skill I need to learn in diving.

 

[fire_diver]

Are you able to control your bouyancy from the moment you dump it all till the second you make it to the surface by simply swimming?

Is there anything wrong in doing it this way? Could any experts comment, please?

Yes, I can control my bouyancy like this. Remember how I said I weight myself. I am only a tiny bit heavy at that point. It's a very easy swim up to the surface.

 

[Crowley]

My BCD is usually almost empty by the time I reach my safety stop - and I tend to dive a kilo overweighted when I am working (makes life a LOT easier sometimes!) and then I can ascend on my lungs alone or swimming if I want. Or upside down, for a good giggle.

If you are doing a swimming ascent, you have to be more or less vertical (more, if you are going up a vertical line). If your buddy, ten feet away, has a problem, you can't swim TOWARD him, because your fins are pointing down. On the other hand, if you are floating up in a horizontal position, you can move forward easily to grasp the line, if need be, or to get to someone to assist them.

This I'm not so sure about - divers swimming vertically to the surface are surely capable of halting their ascent and changing direction, no? It takes me a split second to adjust my position from vertical to horizontal - and - why is the buddy ten feet away on an ascent anyway?

Second - floating up in a horizontal position is all well and good but in my environment, ascending and spinning (in the classic ascent position taught in novice classes) with a 360 degree view of the surface is often essential. If you're surfacing from your safety stop without looking where you're going, and aren't carrying an SMB (or are too far away from the group leader's SMB) there's an awfully good chance of head/propellor/fat tourist interaction!

Of course I am a purely recreational guide and instructor so as long as the ascent is controlled and safe, there's little requirement for any particular technique. I like to make controlled buoyant ascents on my lungs - and many novice divers will ask how I do it so we can begin an extra buoyancy class back on board the boat. Most divers I encounter, regardless of experience level, will use the classic swimming ascent from 5 metres, or swim themselves to the surface at a shallow diagonal close to the reef plate - depends on the dive site.

Don't forget that a diver who is correctly weighted should be able to float at the surface with an empty BC until they exhale completely, so if the diver so negative that swimming to the surface is hard work, they are overweighted. Classic sign of too much lead is an inflated BCD at a safety stop.

Practice in the pool or shallow water - Spend some time getting your weighting perfect, get yourself into a hover and then make minor changes to your depth - both up and down - and take it from there. Keep your deflator to hand, of course, because you don't want to rocket to the surface the first few times you try it. Try it horizontally or vertically, as you like. I tend to start vertically, just for the sake of having a better reference as you head to the surface.

Interesting discussion - have fun perfecting your technique!

Cheers

C.

 

[TSandM]

Oh, I totally agree that, where there is significant risk of surface traffic, the last little bit of the ascent is best done as fire diver describes -- although I CAN scan the surface above my buddy pretty well from 15 feet or so, and he can do the same for me. But being a little negative at the very end of an ascent into crowded waters can be a safety thing. But even I have enough lung volume to manage 1 or 2 pounds negative

Crowley, we can all change position pretty quickly if we need to. But floating up horizontally is restful and easy, and as I said before, makes it very simple to stop -- and at the same time, move forward or backward to maintain position or reach anything you need to reach.

Where the viz is superb and there is no current (or we are drifting), we may well open up 8 to 10 feet between divers. It gives everybody a lot of room to maneuver. I'm not worried about crossing that much distance to donate gas (especially since the other diver will be moving toward me at the same time).

 

[Crowley]

Crowley, we can all change position pretty quickly if we need to. But floating up horizontally is restful and easy, and as I said before, makes it very simple to stop -- and at the same time, move forward or backward to maintain position or reach anything you need to reach.
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I don't wholly disagree with your post TSandM, I just think some divers will not be quite as observant as you - and I LIKE restful and easy; I've surfaced horizontally, on my back, with my legs crossed and my hands behind my head...!

When it's safe to do so, and I am in the company of experienced divers I will make feet first ascents which actually requires a lot of control to do deliberately. I also like tightrope walking or surfing up the mooring lines on the Thistlegorm - bit of current, a LOT of balance and the divers laugh so hard it's a good job there's a hang tank! :cool2:

Note to fun-hating people: I do not advocate doing any of these things at all, until you can control your buoyancy just fine with regular diving, but when you dive three dives a day, every day (except when the government is being overthrown), there's just some times you need a little bit of variation!

Go down smoothly, come up safely,

C.