Buoyancy woes. Need help.

[diverdad87]

I am pretty sure I'm about 4 lbs heavy now.

Now how I've read to test my weight is at the end of a dive, no air in BC, with a normal breath, I should be eye level. Correct method?

Edit: I did see what you said but I was just curious what the difference was for either method.

 

[Quero]

I find that even when new divers are weighted properly, they still often have issues with floating up because of muscle tension in the intercostal muscles that expand and contract the ribcage during the breathing cycle. If these muscles tense up, a diver cannot exhale fully, so whatever volume of air remains in the lungs will add to the diver's positive buoyancy, and up they go, getting more and more frustrated with the result that the muscles remain in a state of tension due to anxiety. I teach students to practice relaxing these muscles on land--I have them tense the ribcage muscles and exhale as fully as they can, and then I tell them to consciously relax the muscles without taking another breath, letting the ribcage contract, and I watch as they find they can exhale further.

The natural "Oh crap I'm floating up again!" reaction is to get tense. You need to counteract that reaction in order to halt those kinds of runaway ascents. Adding extra weight just makes the problem worse because in order to compensate for all the weight and not crawl along the bottom, the diver needs to pump air into the BCD, and all that air expands with relatively slight changes in depth, making it necessary to dump it when going a bit shallower, just to add it again to go a little deeper. Using the BCD as an elevator, inflating and deflating to adjust for depth changes does not allow for fine tuning of buoyancy and of course wastes air you could be breathing!

 

[dpaustex]

I am pretty sure I'm about 4 lbs heavy now.

Now how I've read to test my weight is at the end of a dive, no air in BC, with a normal breath, I should be eye level. Correct method?

Edit: I did see what you said but I was just curious what the difference was for either method.

Well, you normally test your weights at the start of a dive. The idea to be about 4lbs negative is because an aluminum 80 cf tank is about that positive if it's empty.

The main thing is to keep breathing. The tendency is to hold your breath while you're doing something. Again, let give the physics time to work - so if you add air, give it a few seconds to see what happens - and keep your arms and legs STILL (I have students in pool with no fins, and cross their ankles, and no "arm waving").

 

[DevonDiver]

I am pretty sure I'm about 4 lbs heavy now.

Now how I've read to test my weight is at the end of a dive, no air in BC, with a normal breath, I should be eye level. Correct method?

Edit: I did see what you said but I was just curious what the difference was for either method.

At the end of the dive, or on a dedicated shallow dive:

1) Use a larger number of small weights, to allow you to fine tune.

2) Get to your safety stop depth (5m) and establish neutral buoyancy.

3) Get down to min air reserve (50bar/500psi).

4) Attempt to maintain a horizontal trim position, to nullify the chance of sculling or finning.

5) Remove 1 small weight.

6) Release air small (small !) puffs of air from your BCD to compensate.

7) Breath to compensate.

8) If you can still maintain your stop... go back to (4) and repeat.

9) Continue to repeat steps 4-7 until it is physically impossible to maintain your stop.

10) At minimum weight, at 5m, with your tank at minimum reserve pressure, you should have virtually no air in your BCD. Increasing or decreasing the size of your inhalation should be sufficient to easily rise or sink in the water.

11) Repeat the entire procedure every few months, or every 20 dives until you can get your weight down to a bare minimum.

As a guide... I weight about 200lbs. In a 3mm full wetsuit, diving in salt water, I don't need any weight other than my aluminium backplate which is 2lbs. It took me years to get down to that weight... mostly because I didn't know that I could!

 

[Quero]

I am pretty sure I'm about 4 lbs heavy now.

Now how I've read to test my weight is at the end of a dive, no air in BC, with a normal breath, I should be eye level. Correct method?

Edit: I did see what you said but I was just curious what the difference was for either method.

Yes, that's correct.

The difference between doing a weighting check at the beginning of the dive and at the end of the dive is that the air in a full tank has weight, so if you float at eye level at the beginning of the dive, you will be fine at first. But as you breathe the air out of the tank throughout the dive, your tank will get lighter and lighter and it will tend to float you up at the end of the dive, especially at shallow depths.

So we generally recommend adding about 2 kg/5 lbs on top of the amount needed to float at eye level at the beginning of the dive with a full tank. if you adjust your weight at the end of the dive, this isn't necessary, since your tank is already "light." When you are properly weighted, you may feel a tad "heavy" at the beginning of the dive, but you will need this weight to maintain a safety stop when your tank is light at the end of the dive.

 

[TSandM]

diverdad87, I feel your pain! Buoyancy baffled me, when I was new, and I felt the same way you do -- the difference between the bottom and the surface was a single, tiny puff. (You might enjoy reading the journal linked in my sig line.)

Anyway, it's not -- a single puff, that is. But a number of things can make buoyancy very tenuous. People have already talked about proper weighting. The reason that's important is that, if you are overweighted, you have to carry a large amount of air in the BC, and any depth change causes large changes in volume and thus in buoyancy. When you minimize gas in the BC, you decrease instability.

Breathing is VERY important -- and when you begin to become anxious about your buoyancy, you'll likely be tending, as we all do, to hold your breath. This makes you rise.

And, if you are not horizontal in the water, any kicking you do will make you rise, too. It's pretty common to see new divers at about a 45 degree angle to the horizontal. In that position, every time you use your fins, you are driving yourself upwards.

The good news is that thoughtful practice makes things better (and if I can learn to stay neutral, I swear anybody can!) and practice means . . . going DIVING!

 

[NightForce]

What the others are saying about weighting and so on is an important part of the equation. But what finally made the light bulb come on for me was when I finally just STOPPED fiddling with the BC inflator. When I first started to dive I subconsciously thought that for some reason the BC would do all of my buoyancy and trim work for me. It was when I realized that I was relying so heavily on my BC to do the work for me that my buoyancy improved it was a night and day difference for me. Plus before my epiphany I would reach my desired depth and I would just want to take off swimming trying to adjust my buoyancy as I swam bouncing around like a bobber. Now I pause and take the time to become neutrally buoyant BEFORE I take off. With this now I have realized that if I want to go deeper or shallower I adjust my swimming attitude and just swim to the desired position rather than use the inflator to reach the position. At this point as your swimming along if you want to fine tune your depth to get over obstacles you can just use your breathing to raise and lower you. After this amount of control is obtained it will become second nature how to make adjustment to your BC because of changing depths. You will get to the point where the biggest changes will be while ascending and letting air out.

 

[sleepr]

While no where experienced yet, one of the things I have been doing in the pool is settling on the bottom on my stomach and doing no arm "pushups" with just my breathing. I pivot up and down on my toes/fins just by controlling the inhale and exhale by volume and rate. Quite an eye opener as to the amount of control that is generated.

 

[jester1226]

Barely touch the button for inflation. If you can hear the air going in your BC you have held it to long. Don't let this frustrate you, it takes time. Another thing you may doing is adding air to the BC while you have exhaled what was in your lungs, on your next breath the volume in your lungs and BC bring you up. Try adding air while you are inhaling. Hope this helps.

 

[Charlie99]

Reading through the many replies, it might look at first like the original poster is getting a lot of conflicting advice. On deeper inspection though, everyone is really just pointing out different issues and different perspectives on this whole weighting and buoyancy control topic.

Sleepr's comments about no arm "pushups" (I think PADI calls this fin pivots) is kind of like the training wheel equivalent of what DevonDiver would have you doing to find that perfect weighting.

TS&M talks about divers going around at 45 degrees head up and that finning in such a position pushes you towards the surface. I post about developing the ability to stop finning and staying where you are, and stopping your finning every once in a while to check your buoyancy (or using frog kick, which lets you check your buoyancy every glide cycle).

The mentions of getting the right weight, the buoyancy changes from thick neoprene, and Slepr's comments about fin pivots got me thinking about what would be the easiest exercise for a diver to acquire the ability to control buoyancy.

1. No wetsuit. This eliminates the problem of wetsuit changing buoyancy with depth.

2. On a sandy bottom or a pool, so you can start off doing fin pivots or no arm pushups.

3. Having a pile of 1 and 2 pound weights handy. This lets you adjust weight so that your BCD has no air. Like not having a wetsuit, the purpose of this is to reduce buoyancy changes with depth.

4. No fins. This makes it so you won't be kicking and affecting your buoyancy that way.

Once you have gotten setup this way, empty the BCD completely of air. You should end up on the bottom. Start removing weight, a pound at a time, and seeing if you can lift off the bottom when you take a deep breath.

Eventually, you should get to the point where a deep breath will lift your upper torso off the bottom.

Now carefully remove another pound and suck in a deep breath again. Then repeat a couple more times.

At some point of removing weight, you should find yourself lifting completely off the bottom when you breathe in fully, and then settling back down on the bottom when you breathe out.

Take another pound off, and you can do this cycle with a little less full inhale.

Take another pound off. Now you should be able to lift off even easier, but you still settle back to the bottom on a normal exhale.

Do it again, but after lifting off the bottom, EXHALE STRONGLY. You should go very negatively buoyant and go slamming into the bottom.

Remember this trick. If you are starting a runaway ascent, do NOT do as some posters above have noted is the natural reaction and suck in and hold a big breath. EXHALE STRONGLY if you start ascending too fast.

Once you are confident in your ability to drop back to the bottom, take off yet another pound.

Hopefully, by this point, you will start getting the hang of controlling the rate of your liftoff from the bottom and how hard you settle back down. Keep fine tuning this, until you can lift off a foot or 2, and then not quite hit the bottom when your breath out.

The next step is to try and hover a couple feet above the bottom. You will go up a bit when breathing in, down a bit when breathing out. If you can master this, then ascending slowly will come naturally, and will doing a controlled descent.

===================================

By doing all of the above with no wetsuit and no air in the BCD, you avoid any significant buoyancy changes with depth.

The next step in really learning buoyancy control would be to add back 2 or 3 pounds, then put a little bit of air into the BCD to compensate. You should still be able to do ascents controlled by your breathing, but you will have to correct buoyancy by changing lung volume more than before, as now you have to compensate for the expansion of the air in the BCD as you rise.

Trying to control your buoyancy at a safety stop while wearing a wetsuit adds a bit more instability as the wetsuit expands as you rise.

Having a full tank of air adds extra weight that you need to compensate for by adding air to your BCD, which adds a bit more instability.

Being overweighted forces you to compensate by adding more air to your BCD, which adds a bit more instability.

Start with the simplest condition of no wetsuit and no air in the BCD and work into the more unstable conditions afterwards.

Work to make your automatic, ingrained response to beginning a runaway ascent is to exhale strongly.

===============================

This is a long post, but that's because I tried to lay out each step and the reason behind it.

What we really need at this point is for someone that is just learning to control their buoyancy to come back and tell us what worked for them.

Charlie