Inflating BC during ascent?
- Thread starter kat.hayes
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
You shouldn't be inflating your BC at all to ascend, and you should be breathing normally.
You add air during descent to increase bouyancy (to neutral) to overcome the compression/loss of bouyancy as pressure increases. When you ascend, you should be slowly swimming up and venting air from your bc to remain neutral all the while breathing normally and never holding your breath.
You add air during descent to increase bouyancy (to neutral) to overcome the compression/loss of bouyancy as pressure increases. When you ascend, you should be slowly swimming up and venting air from your bc to remain neutral all the while breathing normally and never holding your breath.
elan
Contributor
Kat, it's actually DANGEROUS to do it. It's going to cause a chain reaction. You inflate it - you ascent more, the air expands and makes you ascending more and then you pop out like a ball.
As it was said you actually maintain neutral buoyancy and swim up slowly, slowly RELEASING air from the BCD.
And constantly breath as expanding air can cause injuries if you do not have the airways open
vladimir
The Voice of Reason
- Messages
- 44,765
- Reaction score
- 65,516
- # of dives
- I just don't log dives
I don't swim up. I get slightly positive--a large inhale will do it--and remain positive and relatively motionless the whole way up, venting air in the bc as needed to prevent acceleration of the ascent rate.
1. Is this absolutely frowned upon, adding air to a BC to ascend or is it something that is done sometimes. Just curious.
2. What exactly does wetsuit compression mean? Is this the wetsuit wrapping tighter around your body resulting in less buoyancy during a descent?
Thanks.
2. What exactly does wetsuit compression mean? Is this the wetsuit wrapping tighter around your body resulting in less buoyancy during a descent?
Thanks.
elan
Contributor
1. If you are actually ascending adding air to the BC will speed up you ascent.
2. The wetsuit becomes thinner. You can say it's wrapping tighter only if you have air spaces between the wetsuit and the body.
If this isn't a joke...then you don't inflate and for God's sake don't hold your breath while you ascend. You're asking for trouble.
Achieve your neutral buoyancy, start your ascent and release the rest of your air as your start swimming up. Breath normally and inflate your BC after you surface.
Reread your OW manual...please.
(this is my first snarky post on SB - I feel so much closer to you all now.)
Achieve your neutral buoyancy, start your ascent and release the rest of your air as your start swimming up. Breath normally and inflate your BC after you surface.
Reread your OW manual...please.
(this is my first snarky post on SB - I feel so much closer to you all now.)
Last edited by a moderator:
hudson
Contributor
You can add air temporarily only when you were NOT neutral to begin with for whatever reason, to be dumped as you start the ascent. You can also add some air if you end up dumping too much air during the ascent, but you need to be very careful and in control about these things. A stuck inflator in this phase could be very dangerous.
The key point is never make the mental association that adding air means ascend. There is a big difference between initiating ascent and stopping descent.
Kind of.. more than wrapping tighter around your body, it's getting thinner as the air bubbles inside the neoprene material of the wetsuit are getting compressed, therefore losing buoyancy. The reverse occurs on ascent.
NudeDiver
Contributor
Wow.
Kat - it's basic physics. The air that is already in your BC is going to expand as you ascend. You can't prevent it. What you do is vent air as you ascend, to avoid a run-away ascent. You certainly do not want or need to ADD air to your BC when you ascend - only when you are at the surface and want to help ensure you stay at the surface. So yes, adding air to your BC is generally highly frowned upon - as it is a bad idea.
On wetsuit compression - it's the same thing. A neoprene wetsuit has little gas bubbles trapped in the material. As you descend, those gas bubbles compress, causing the suit to lose buoyancy. As you ascend, the previously compressed gas bubbles in the suit will now expand, thus increasing buoyancy.
So, the net effect of all of this is that as you ascend, the gas in your BC and the gas trapped in the air bubbles in a neoprene suit is all going to expand - and want to make your ascent rate increase at an ever faster rate - UNLESS you vent air from your BC on the way up. If, instead, you ADD air to your BC, you will not only fail to counteract the increasing buoyancy you already have, but will ADD to that, increasing your ascent rate even more.
So, overall, bad idea.
Kat - it's basic physics. The air that is already in your BC is going to expand as you ascend. You can't prevent it. What you do is vent air as you ascend, to avoid a run-away ascent. You certainly do not want or need to ADD air to your BC when you ascend - only when you are at the surface and want to help ensure you stay at the surface. So yes, adding air to your BC is generally highly frowned upon - as it is a bad idea.
On wetsuit compression - it's the same thing. A neoprene wetsuit has little gas bubbles trapped in the material. As you descend, those gas bubbles compress, causing the suit to lose buoyancy. As you ascend, the previously compressed gas bubbles in the suit will now expand, thus increasing buoyancy.
So, the net effect of all of this is that as you ascend, the gas in your BC and the gas trapped in the air bubbles in a neoprene suit is all going to expand - and want to make your ascent rate increase at an ever faster rate - UNLESS you vent air from your BC on the way up. If, instead, you ADD air to your BC, you will not only fail to counteract the increasing buoyancy you already have, but will ADD to that, increasing your ascent rate even more.
So, overall, bad idea.
don Francisco
Contributor
Kat, as the others have said, don't add air to your BC on ascent, vent it as it expands.
There's nothing in your profile, but from the question, I assume that you're still a student or at least a very new diver. Read NudeDiver's explanation and make sure you understand it at a gut level. It's a good explanation of fundamental bouyancy dynamics and unless you have a good grasp of the principle involved, you'll never master bouyancy control.
There's nothing in your profile, but from the question, I assume that you're still a student or at least a very new diver. Read NudeDiver's explanation and make sure you understand it at a gut level. It's a good explanation of fundamental bouyancy dynamics and unless you have a good grasp of the principle involved, you'll never master bouyancy control.
Similar threads
