Possible to remain completely neutral when deploying SMB?

I am still floating up slightly (2-3m) when deploying my SMB. I was taught to be neutral before deployment, ie no dumping of air completely before deployment to make myself more negative.

I was shooting the SMB at 17m. Its a 2m SMB if that matters. I was taught to take about 3/4 breath and breathe out fully into the SMB. this will transfer the volume of my expanded chest to the expanding SMB, making me only slightly buoyant (as if I'm holding my breath at 3/4 lung capacity).

Although I stop breathing in till after I let go of my SMB I still find myself floating up quicker than if I had just held the same air in my lungs.

I have 2 questions:
1) what is the reason (physics) behind this behaviour that you are more buoyant when you transfer the air in lungs to SMB?
2) what is the trick or technique to avoid floating up as much as possible?

I know if I only take 1/2 a breath I will probably be more neutral but my SMB is a big one and 1/2 breath may not be enough to sufficiently inflate it to make it visible/vertical.

I also prefer the 2m SMB because the 1m one is not very visible when there are waves on the surface.

Thanks!

Another method is to dump your wing into the smb. This means absolutely no changes in bouyancy until you let go of the smb. You can remain neutral and hold on to the smb while dealing with a possible entangelment etc.

Just something to add to the argument/discussion.

Use the Bolt Snap method. It'll fix your issue.

WhiteSands:

I am still floating up slightly (2-3m) when deploying my SMB. I was taught to be neutral before deployment, ie no dumping of air completely before deployment to make myself more negative.

I was shooting the SMB at 17m. Its a 2m SMB if that matters. I was taught to take about 3/4 breath and breathe out fully into the SMB. this will transfer the volume of my expanded chest to the expanding SMB, making me only slightly buoyant (as if I'm holding my breath at 3/4 lung capacity).

Although I stop breathing in till after I let go of my SMB I still find myself floating up quicker than if I had just held the same air in my lungs.

I have 2 questions:
1) what is the reason (physics) behind this behaviour that you are more buoyant when you transfer the air in lungs to SMB?

Click to expand...

Probably just timing. If you're neutral at 1/2 lung volume, then you're gonna be positive at a 3/4 breath by 1/4 of a breath. So that's your starting point, you're already positive. You blow that into your SMB and you're still 1/4 positive. So far it's been the same as if you'd been holding your breath at 3/4, but some time has passed, so you went up a little already. But now your lungs are empty and you breathe in again. If you take your usual 1/2 breath, then now you're 3/4 positive and you go up even faster.

Other than that, there's nothing that could possibly cause the behaviour you mention. The solution (without changing your methodology) would be to just be quicker with letting go of the SMB

I use my flippers to swim head down just a tad while I fill it up. When I let it go, I make my flippers stop and then I'm neutral again.

Also helps to fill it up deeper so you don't have to put as much air in the bag to fill it because it expands.

Hook a double ender or bolt snap to the line on the reel. Let out about 6' of line. The Double Ender will pull the line down tight, so it's not floating all over the place like a big mess. Then, fill the bag hard as you can with your regulator, making sure your reel is ready to pay out line. As the 6' of slack is pulled up, the double ender will rise in front of you until all the slack is gone (while the bag is shooting toward the surface). Once all the slack is out... remove the double ender.

This method gives you a good 5 seconds of leeway. As long as your reel or spool spins freely, you should be fine.

Superlyte27:

Hook a double ender or bolt snap to the line on the reel. Let out about 6' of line. The Double Ender will pull the line down tight, so it's not floating all over the place like a big mess. Then, fill the bag hard as you can with your regulator, making sure your reel is ready to pay out line. As the 6' of slack is pulled up, the double ender will rise in front of you until all the slack is gone (while the bag is shooting toward the surface). Once all the slack is out... remove the double ender.

This method gives you a good 5 seconds of leeway. As long as your reel or spool spins freely, you should be fine.

Click to expand...

I don't have the same problem as the op but id like to try that method to see how good it works,





What I do is I breathe out while at the same time purge my reg a little for that additional air... As the SMB is going up im still breathing out just to ensure that I dont become bouyant








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WhiteSands:

I am still floating up slightly (2-3m) when deploying my SMB. I was taught to be neutral before deployment, ie no dumping of air completely before deployment to make myself more negative.

Click to expand...

This isn't easy, and it's part timing, breathing, and depth. I assume you use a closed circuit SMB so you actually have to breath into it rather than fill it with your reg.

Like was mentioned above, if you're just going to use the volume in your lungs without other measures (kicking down, etc.), then it helps to be slightly negative while holding your depth by keeping your lungs mostly full. This may require you to dump a small amount of air, but will allow you to get a good full breath into the buoy without changing your buoyancy too much. Then you got to let it go quick.

Like was also said, shooting at depth makes it easier as a smaller breath makes a bigger impact at the surface. That's easy to do on square profile dives, but more of a pain if you are on a slope in and out of the dive.

I'd recommend the mostly full lungs and swimming down combo, especially for shallow deployments. Deeper down it doesn't matter as much.

Whitesands-watch a new diver practicing trying to stay neutrally boyant. Most of em will bob up and down a meter or so as they work out their breathing. Sounds to me like you are doing something similar. Ie your breathing is out of sync.
Dag namb it I know I'm saying this wrong--can someone make sense of this??

Superlyte27:

Hook a double ender or bolt snap to the line on the reel. Let out about 6' of line. The Double Ender will pull the line down tight, so it's not floating all over the place like a big mess. Then, fill the bag hard as you can with your regulator, making sure your reel is ready to pay out line. As the 6' of slack is pulled up, the double ender will rise in front of you until all the slack is gone (while the bag is shooting toward the surface). Once all the slack is out... remove the double ender.

This method gives you a good 5 seconds of leeway. As long as your reel or spool spins freely, you should be fine.

Click to expand...

Thanks for explaining the bolt snap method, Peter. This method works with oral inflation too, not just open-ended bags. A lot of folks use a simple sausage that can only be inflated orally. By separating the lift as you exhale from the spool in your hand, you gain a few seconds of normal buoyancy.