It's been sort of mentioned before (on this page) but just to reinforce things. Take your gear to a pool. Test each major component for it's empty buoyancy and full buoyancy (if needed). Do a little math exercise and start from there.
Take 2 tanks of a type you normally use; one with 500 psi in it and the other full. Then in turn put your regulator and BC (with it COMPLETELY EMPTY) together WITHOUT WEIGHTS on each tank and see what you need to either sink it, or float it. (sink it with adding 1# of lead at a time and float it by hanging it from a fish scale). Next, with a tank/regulator next to you on the bottom find out how much it takes to just barely keep you on the bottom with your feet crossed at the knees and your hands held together. It doesn't matter what position you are in. Do this with your lungs as empty as you can, and at a comfortable breathing level.
You can also do this without tanks. Just take the empty BC and fold your regulator into it (dustcap ON) and see how positive or negative it is. You can look up the buoyancy of tanks easily.
Once you know the buoyancy (negative or positive) then you can add them all together and get a starting point of what you should need for weight. Anything more is probably trapped air in the BC or in your lungs (anxiety).
Good luck.
Take 2 tanks of a type you normally use; one with 500 psi in it and the other full. Then in turn put your regulator and BC (with it COMPLETELY EMPTY) together WITHOUT WEIGHTS on each tank and see what you need to either sink it, or float it. (sink it with adding 1# of lead at a time and float it by hanging it from a fish scale). Next, with a tank/regulator next to you on the bottom find out how much it takes to just barely keep you on the bottom with your feet crossed at the knees and your hands held together. It doesn't matter what position you are in. Do this with your lungs as empty as you can, and at a comfortable breathing level.
You can also do this without tanks. Just take the empty BC and fold your regulator into it (dustcap ON) and see how positive or negative it is. You can look up the buoyancy of tanks easily.
Once you know the buoyancy (negative or positive) then you can add them all together and get a starting point of what you should need for weight. Anything more is probably trapped air in the BC or in your lungs (anxiety).
Good luck.