Descending Vertically Vs Horizontally

[derwoodwithasherwood]

What type of equipment are you using? It's common for someone in a jacket bcd to think they let all the air out of their bcd, but they really have some trapped inside.

I have found that to be true of the wetsuit too. Sometimes it takes a while for all the little bubbles to work their way out.

 

[ScubaTwo]

I have found that to be true of the wetsuit too. Sometimes it takes a while for all the little bubbles to work their way out.

My wet suit is very ill fitting. To small on bottom to big on the top. When I dive with a skin or just a swim suit I have no probs descending. You might be onto something here.

 

[ScubaTwo]

I do know tho that my biggest prob is not letting all the air out of my lungs. My instructor has actually watched me face to face (yes it was hard not to laff let alone let all the air out) but I totally dont agree with saying you shouldnt let all the air out of your bcd. If someone can cotrol their bouyancy without leaving any in there is no prob. If you can do so then you only need air in it at the surface. no?

 

[scubafool]

ScubaTwo, the tank that is on your back gets more bouyant as you use(breath) the air that is in it. At the start (descent phase) of the dive, the tank is at it's most negative point. Therefore, at the start of your dive, all other things being equal, you need MORE air in your BC to achieve neutral bouyancy than you do at the end of your dive. So therefore, I maintain that you shouldn't need to dump all of the air to descend at the start IF you completely exhale AND you are truly able to dump ALL of the air at that time. Note that I did not say descend like a rock, just descend.

 

[ScubaTwo]

So therefore, I maintain that you shouldn't need to dump all of the air to descend at the start IF you completely exhale AND you are truly able to dump ALL of the air at that time. Note that I did not say descend like a rock, just descend.

Now your just confusing me!

 

[jepuskar]

I sometimes add bubbles to my wetsuit during a dive, but that's a whole other topic.
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Whether you dump all the air out of your BCD or just some to start your descent is irrelevant as long as you start your descent.

What is relevant though is maintaining a controlled descent. You don't want to get in the habit of hitting the bottom and then adding air. Add air in short bursts on your way down to remain slightly negative and then get nuetral once you have reached your depth. Yes, not letting all the air out on the surface and still descending does save you some tank air on descent, but if your that obsessed with conserving your air then don't use your power inflator and orally inflate on the way down.

With 500psi in your tank at 15ft with no air in your BC, you should be able to easily stay nuetral. If your struggling to stay down or up, than your weighting needs to be adjusted accordingly. One final way to check this is the buoyancy check at the surface as described above.

Jason

 

[scubafool]

If you can do so then you only need air in it at the surface. no?

A wetsuit (and I am ASSuming that you wear a wetsuit) compresses and looses bouyancy when you descend, the deeper you get, the more bouyancy it loses. Hence the BC (bouyancy COMPENSATOR) is needed, to COMPENSATE for the loss of bouyancy that the wetsuit provides at the surface. So in a wetsuit, you should need less air in your BC at the surface than at depth, tank bouyancy being the same.

 

[scubafool]

Now your just confusing me!

Oh, NO, I thought that I was the only one around here that was confused! We need to find someone who knows what they are talking about!

 

[ScubaTwo]

A wetsuit (and I am ASSuming that you wear a wetsuit) compresses and looses bouyancy when you descend, the deeper you get, the more bouyancy it loses. Hence the BC (bouyancy COMPENSATOR) is needed, to COMPENSATE for the loss of bouyancy that the wetsuit provides at the surface. So in a wetsuit, you should need less air in your BC at the surface than at depth, tank bouyancy being the same.

I understand what you are saying and respect your position. I would appreciate you not talking to me like Im an idiot.

 

[scubafool]

ScubaTwo, the tank that is on your back gets more bouyant as you use(breath) the air that is in it. At the start (descent phase) of the dive, the tank is at it's most negative point. Therefore, at the start of your dive, all other things being equal, you need MORE air in your BC to achieve neutral bouyancy than you do at the end of your dive. So therefore, I maintain that you shouldn't need to dump all of the air to descend at the start IF you completely exhale AND you are truly able to dump ALL of the air at that time. Note that I did not say descend like a rock, just descend.

OK, maybe I can do better this time. Probably not, but I'll try.

Your tank is HEAVIER in the water when it is full, & LIGHTER in the water when it is nearly empty. Heavier full, lighter empty. At the beginning of a dive the tank is full, so the tank is heavier. At the end of a dive the tank is nearly empty, so it is lighter. Now, with the tank being lighter at the end of your dive, if you can hold a really shallow stop with no air in your BC, you would need MORE air in your BC to hold the same stop at the start of the dive (remember, your tank would be HEAVIER).

So how did I do?