Silly question, first of many in sure LOL

[D Powell]

Is your BCD completely deflated when you finish your dive and surface?

The reason for asking this is that you are weighted down to sink so how do you surface if its empty and kept empty when surfacing.

Thanks for your help.

 

[Ber Rabbit]

You should be weighted to be neutrally buoyant at 15 feet with 500psi of air in your tank and no air in the bc; in other words you should be able to hover there. Some gear configurations are heavy (ex: doubles) so you need to have some air in the bcd to be neutral.

When you have no air in your bc you gently kick to ascend, some people can do the ascent from 15 feet by simply altering their breathing pattern. Once you reach the surface you add air to the bc so you can float without having to tread water.

Hope this helps!
Ber :lilbunny:

 

[Don Burke]

Is your BCD completely deflated when you finish your dive and surface?

That is the plan.

The reason for asking this is that you are weighted down to sink so how do you surface if its empty and kept empty when surfacing.

Thanks for your help.

The dive is started with the diver being heavy by the amount of gas in his cylinder above his planned ending pressure. At the end of the dive that extra gas is gone, so he should be neutral with an empty BC.

Swim up and inflate the BC once on the surface.

 

[dkktsunami]

Is your BCD completely deflated when you finish your dive and surface?

The reason for asking this is that you are weighted down to sink so how do you surface if its empty and kept empty when surfacing.

Thanks for your help.

If properly done you are weighted to achieve neutral bouyancy, not to "sink". When you begin the decent the bc should be emptied. If you are wearing a neoprene wet suit it will compress as you go deeper therefore it will be necessary to add a little air to your bc to remain neutral. As you ascend this air will expand so it must be released a little at a time to remain neutral. Ideally you should use gentle kicks to "swim" up slowly. Once on the surface bc should be inflated so diver can maintain positive bouyancy.

 

[joe rock]

Is your BCD completely deflated when you finish your dive and surface?

The short answer is maybe. There are many variables that effect your buoyancy. And everyone is going to have a different set of condiitions.

I dive mostly in cold water, have my own amount of buoyancy and wear a 7mil farmer john. The buoyancy of wet suits change at depths due to compression of the neoprene. Close to the surface - LOTS OF BUOYANCY. An empty tank has more buoyancy than a full tank. So depending on how much air is left on ascent, your buoyancy will be different.

That's why you hear so much about the proper weight to achieve neutral buoyancy with an "empty" tank, and you need to check your weight when you change diving conditions (fresh v. salt water, different tanks, different exposure suits etc.)

In order for ME to "stay down" for my safety stop, I must almost completely dump the air in my BC.

 

[Missdirected]

Whew....so I am doing it right, lol!

 

[ajames54]

At the end of your dive your tank is closer to empty and therefore weighs less, so you are MORE boyant and it takes less weight to keep you down. If you end your ascent with much air in your BCD it means that you were quite likely overweighted at depth.

Most suggest you check your weighting and try to be neutral with a tank that is at the 500PSI point. Personally I try to be slightly negative at the end of a dive since it makes maintaining depth at a safety stop easier (for me YMMV).

 

[D Powell]

If properly done you are weighted to achieve neutral bouyancy, not to "sink". When you begin the decent the bc should be emptied. If you are wearing a neoprene wet suit it will compress as you go deeper therefore it will be necessary to add a little air to your bc to remain neutral. As you ascend this air will expand so it must be released a little at a time to remain neutral. Ideally you should use gentle kicks to "swim" up slowly. Once on the surface bc should be inflated so diver can maintain positive bouyancy.

So if you are neutrally bouyant at 15 feethow difficult is it to do this at 50 or 100 feet?

Thanks again for your help.

 

[pasley]

So if you are neutrally bouyant at 15 feethow difficult is it to do this at 50 or 100 feet?

Thanks again for your help.

That my friend is why you wear a BC, so you can add air at depth to compensate for the loss of buoyancy from the compression of the wetsuit. Just add very short psssst and wait several seconds for the air to overcome the inertia before you add more. That pause is key. Many new divers add air, are dropping due to inertia and add more. Then the air from the first pssst overcomes the inertia and they have already added more and now they are too buoyant. So add a little, wait, and if necessary add more.

 

[Ber Rabbit]

At the end of your dive your tank is closer to empty and therefore weighs less, so you are MORE boyant and it takes less weight to keep you down. If you end your ascent with much air in your BCD it means that you were quite likely overweighted at depth.

Small problem with this statement, if you are MORE buoyant you need MORE weight to keep you down.
Ber :lilbunny: