Buoyancy control and orientation in the water?

[GregA2k6]

Once again....thanks for everyone's help with my question!

It is appreciated.

GregA

 

[khacken]

On breathing, slow is good, but don't fill your lungs all the way up, or you will start to yo yo on each breath. When I did my pool dives I thought slow and deep meant sucking in as much air as possible on each breath. If you do that, you will never get the buoyancy right.

Think about how you breathe when you are about to fall asleep. My instructor gave me that tip, and my buoyancy improved right away.

 

[donacheson]

You are correct. It WILL take some experience to get a grasp on bouancy control. However the first thing that would help (beside a BCD that didn't leak) is to perform a weight test. You should enter the water with all your gear and a tank that is near empty. Then move to an area that is slightly "over your head". Let all the air out of your BCD and then take a normal breath and hold it in. You should float about "eye level". Exhaling you should start to sink.

If you are not "eye level" with a normal breath, adjust weights accordingly. If you are above the water more then add a small amout of weight then try it again until you get it right. If you sink then take small amounts of weight off and repeat until you get the right amount of weights.

If you do the weightcheck in freshwater then dive in salt you will need to add about 6 pounds.

Then remember how much weight was required. Also remember what you were geared in while testing. ie. 7mm fullsuit, 3mm shortie, etc. What BCD? What size tank? Aluminum or Steel? If your configuration changes then you need to do a weight check in that gear.

Hope this helps.

Jeremy

Why not do it right?

A sports diver should minimize the weight of lead carried. The minimum weight is that required to keep the diver neutral with an empty BC, near empty tank, just below the surface, while breathing normally. This weighting the allows a comfortable safety stop at 10 to 15 feet at the end of dive and a controlled ascent to the surface.

Minimal weighting is not difficult to attain. It's easily done in a pool or other shallow water. Adjustments for fresh/salt water are easy: a diver needs an additional 2.5% of his total weight - diver plus all of his gear in salt water. The adjustment for more than an empty tank are equally simple: add 1 pound for every 13 cubic feet of air (about 500 psi for an Al 80) in the tank.

 

[SangP]

GregA2k6,

Your are way ahead of me when I first started. First, don't overweight yourself as it could create buoyance problems at dept. Ask the dm and others around before your dive and look for someone of your similar built and has the same sort of equipment (BC). At most place 2-4 pounds more than the other guy or dm.

Next your problem of legs sagging the same as myself. I have heavy feet... long legs, short body problem. I can almost always stand in the water unless my weighting is perfect.

Go slow on your decents, blow out all the air in your bcd and also your lungs and when you first begin to sink, push a bit of air into your bc every 5 feet. Once you are about 10 feet from the bottom, inflate more air till you can come to stop about 3-5 feet from the bottom.

I tend to air my wings about 7-10 feet from the bottom.

Cheers,

SangP

BTW, my trim problem was only solved after I properly weighted my BP/W with weights on my tank straps.

 

[markfm]

Attached are some notes I put together on weighting.

They are related to the mechanical things -- compensating based on how many PSI are in your tank when you do get neutral, switching tank types, etc.

Simple practice, getting dives in often, has a huge impact on weighting as you get more comfortable, better trim and style. The PDF gives you the math, but the touchy-feely part of style made the difference between 18 lbs during cert/initial dives and 12 pounds now, for the same configuration (I can actually dive the same config at less, but am working towards DM, starting to purposefully carry more weight).

As always, take everything you see on the 'Net with a shaker of salt.

 

[Blue Kangaroo]

Ok, i agree with all the technical advice and math but how much weight a diver ( esp a student) carries is really dependent on how he breathes. Yeah, size, exposure suit and all the obvious stuff apart.

So....try this. At 7 mtrs with a buddy close to you, empty your BCD and remove your weight belt. Hold on to the free end, and then lay down the lead, block by block. The only way you will be able to do this is really relaxing and using very small controlled breathing. Eventually you will be able to kneel on the bottom, with NO weights lifted at all. OBVIOUSLY KEEP A HOLD OF THE SLACK BELT FOR SAFTEY AND HAVE YOUR BUDDY READY TO SUPORT YOU IF YOU BECOME BUOYANT. DO NOT DO THIS UNSUPERVISED !!!!!!!

Now this will show you that your body can survive with only very limited shallow breaths. Clearly this is not good way to breath for the entire dive but it demonstrates how overweighted people are.

Now consider this....
Weights will drag your waist down. Compensation for this is putting air in the BCD. So what ? Well an inflated BCD is designed to hold you upright. The more air you have the for vertical you will become. You will then fight this by using yout leg and torso muscels. This in turn means taking deep breaths as the lungs are really just slaves. So a deep breath means buoyancy. With the air already in the BCD now expanding you head upward.

Good buoyancy comes as a result of relaxed, controled breathing. The weighting is secondary to this.

Try to think along these lines and visualise your lungs expanding an adding lift. I always tell my advanced students to just consider their breathing as a involuentary response. If you work harder you breathe deeper.

There is plenty more to add but hope these ideas my help.