lung volume buoyancy control

[gzscuba]

Hi all,

My buddy and I (both recently certified) have been diving at Devil's Lake, WI (one of the local lakes). We've just been doing some practice on buoyancy control in the shallows, since there isn't much worth seeing below 15 ft. The first set of dives we did got me pretty frustrated. I just ended up bouncing off the bottom and the surface. I'm sure anyone watching would have been very amused.

Anyway, we went back last weekend with some slightly more positive results. I had read the PADI Peak Performance Buoyancy section of my AOW book and really tried to focus on using my lungs to fine tune my buoyancy. It seemed to really help. After a bit I wasn't bouncing off the surface and bottom There was still a noticeable change in depth between breathing in and out, though.

I did hit a little snag though. At one point, I was 15 feet down and I needed to flood & clear my mask (it was fogged). So I stopped - I think I was hovering at the time. I closed my eyes, flooded,took a deep breath, blew out and cleared..... and oops, I was almost at the surface. I dumped a bunch of air from my BC and got back down.
Should I have tried to mask clear with multiple smaller breaths? Should I have dropped some air from my BC to get slightly negative?

At the end of the dive, I was able to pretty much control my ascent with lung volume, and a bit of BC dumping - I tried to get it so that I only rose when I my lungs were mostly full.

In all, I'm feeling a lot better about my limited dive skills. Right now, staying at a consistent depth without a reference keeps me pretty task-loaded, but I can do it (I have stare at my gauges).

I'd appreciate any comments, suggestions, or critiques.

 

[Welshman]

The PPB course helped me a lot too.

However, have you got your weighting right. When you said you had to dump a lot of air from your BC to get down having almost come up from 15 feet, my thought was why do you need a lot of air in your BC at 15 feet? Try the recommended test - get a tank with 500 PSI and weight yourself so that with no air in your BC and holding a normal breath you float on the surface with your eyes at surface level - when you exhale you should gently descend.

I would expect you to have no air in your BC at 15 feet if you are properly weighted. You should only need to add air to your BC at greater depth to offset the reduced inherent bouyancy of your wetsuit through compression.

Hope this helps.

Regards

 

[art.chick]

...and my other thought is that perhaps you were really huffing air for that big exhale into the mask. You don;t need to inhale so much; just the normal amount, then gently blow out (I think many are trained to stare up too far to clear the mask; also not needed.) And clearing should not take too long. Some newbies make a real production of it. Quick flood; quick exhale, seal of mask barely broken. See if that helps some too.

 

[MikeS]

Welshman once bubbled...
I would expect you to have no air in your BC at 15 feet if you are properly weighted.

Welshman,

I would think that at the start of the dive there should be enough air in the BC to provide lift equal to the swing weight (difference between full and empty) of your tank. Otherwise, if you were neutral at the start of the dive with no air, you would become positive as you used air and not be able to release air to compensate.

Mike

 

[landlocked]

Sounds to me like you are doing well in the learning process. Maintaining bouyancy while task loaded is what I am currently working on. It isn't all that easy is it. But if it was easy, would it be as fun?

 

[WreckWriter]

gzscuba once bubbled...
I closed my eyes, flooded,took a deep breath, blew out and cleared..... and oops, I was almost at the surface.

You should be able to clear your mask on a normal breath with minimal exhalation. It only takes a tiny bit of air to fill your mask with air, thereby displacing the water, it doesn't require a full lung blow.

Sounds like you just need a bit of practice. Take it slow

Tom

 

[O-ring]

Landlocked is dead on, IMHO. Just keep at it...remember, at those depths you are going to see the most swing in buoyancy, hence you are practicing at the "hardest" depths. If you can get it down at 15-20 feet, you will have no problems at deeper depths.

 

[jbd]

advice has been given. I just want to encourage you to keep practicing what you are doing. Try not to get overly frustrated when it doesn't workout. With time and the focused effort you are making things will get better. These may not be the most fun dives but IMHO you are doing the really important thing at this time by concentrating on skill development.

Have you checked out the threads about the DIRF classes that some of the folks have taken. If not please do so. It will give you an idea of what level the bar is at. Gives you a goal to work towards.

 

[earl]

Hey -- just when I thought there weren't any locals here. FWIW, I live in Madison, and I'm normally at 3LD for the Tuesday night dive and Sunday afternoon. I'll try to catch you sometime.

-earl-

 

[Welshman]

Mike S

Good point which I had forgotten to mention, but i think basic weighting technique is right - you need to be correctly weighted for the end of the dive otherwise you'll have a problem with making a gradual ascent which may or may not include a 5m safety stop. However, even at the start of a dive i wouldn't expect to have much air in my Bc at 15 feet.

Thanks for the additional comment

Regards