Deploying a SMB

[alan_lee]

I'm still new to the deployment of SMB after learning it during my AOW, and I seem to have a problem with deploying it such that it can stay upright at the surface of the water. I'm wondering if the problem lies in how much air I purge into the SMB. What I do is that I'd let go of the SMB as soon as I feel it tugging upwards. I'd usually deploy the SMB between 6-10m depths.

Am I doing something wrong?

Thanks!

 

[Rainer]

What size SMB are you using? I use a Halcyon 3.3' marker (6# lift) that I can basically fully inflate at depth, easily hold, then launch when I'm ready. I had a devil of a time shooting a 50# bag at "shallow" (<50') depths and having it be anywhere near full when it got to the surface. Damn Boyle's Law...

 

[rockjock3]

It isn't going to stand up unless you are pulling down on it. Depending on the size of the SMB and the surface conditions it will require more/less pressure on the line to keep it upright. Even if you are not filling it up all the way the air-filled portion will stand up if you pull down on the line.

If you want to ensure it is totally filled then you need to fill it with air to a point that will allow it to be totally filled at the surface. For example. If I am at ~33fsw/10m, then I need to fill my SMB 1/2 full for it to arrive at the surface completely filled. When I launch from ~70fsw/21m-ish then I only fill it about 1/3 full.

 

[alan_lee]

I think mine's about the same size. The reason why I don't fully inflate it is cos I'm figured that if I don't have to do a full inflate because by the time it gets to the surface, the air would've expanded due to Boyle's Law. Plus there's also the worry that I'm gonna get carried to the surface if I hang on to it. From what I was taught, you do not fully inflate the SMB else it won't be able to stay erect at the surface. Is that right?

 

[Wildcard]

I think people expect the SMBs to be standing on end all the time. Unless your hanging on the line, it wont. They will stand up for a second at the top of the swell than lay back down. One reason I feel bigger is better, the limp sausage will still be visable. I have a 6 footX8inch yellow and orange lift bag that can be seen from space.

 

[redacted]

Standing tall may be important for getting the attention of distant boats. But for protection from close in boats as you surface, even a partially inflated marker should work fine if the boats are looking. Keeping it dancing around should help it be seen. After you have surfaced, you can fill it up more if necessary.

I try to shoot my marker from about 30 ft to 45 ft to give Boyle a chance. Much shallower than that and I know I'm not going to get my 50 lb bag full unless I am overweighted. At 30 to 40 ft, that bag need to be 20 to 25 lb positive bouyancy to be full at the surface. When I deploy my marker, I make sure the valve (duck bill style) is not stuck shut first. Then I empty my wing into the bag so bouyancy is unchanged and the bag is straight up and I can confirm it is OK. Then I fill the bag slowly from my reg until I feel I'm starting to lose bouyancy control. Then I exhale, give it a good last shot, let it go and watch the dancing spool. The result is usually adequate but notheing to brag about.

 

[Doc Harry]

I have had similar issues. Here's what I learned:

You're never going to get an SMB to fully inflate from 10m. If you try to hold onto the SMB long enough to fully inflate it at that depth, you'll be on a rocket ride to the surface. Your options are a) be satisfied with what you get, b) deploy at a deeper depth, or c) get a smaller SMB.

a) Be satisfied with what you get. You don't need an SMB fully inflated when you deploy it. Once on the surface, you can always blow more air into it.

b) Deploy the SMB from a greater depth. The expanding air will fill the SMB more.

c) Get a small 3 foot SMB for deployment from depth. Some are only 3 inches in diameter and don't require a large volume to fill. Get a separate BIG 6 footer for emergency surface deployment.

BTW, unless you pull constant tension on the line the SMB will fall over regardless of the SMB size.

 

[TSandM]

I sort of disagree with Doc Harry.

If you have a 1m SMB (the common size) then one full breath at 10m should result in a nearly full bag at the surface, unless your lungs are smaller than mine (which I find difficult to believe of anybody who isn't eleven years old).

However, it is true that you have to manage your buoyancy, to blow a full breath into a bag and control it before release. The way to do this sounds more complicated than it is to do: Get the bag out and ready to inflate. Take a deep breath and hold it (airway open, of course) and check buoyancy. Adjust as necessary so that you are NEUTRAL with a full breath held. Position yourself slightly head down, too, so you can fin down if you have miscalculated.

Once you are neutral with full lungs, blow a full breath into the bag. You haven't changed the total air volume at all, just the location. Maintain full exhalation while you okay the team and check above you. Release the bag and take a full breath -- buoyancy is still neutral. Now, as the bag is proceeding to the surface, adjust your buoyancy to very slightly negative with normal breath. Then you can keep a small amount of tension on the line, keep the bag upright, and maintain neutral buoyancy.

Takes four paragraphs to write, and seconds to do, once you get the sequence sorted out.

 

[Doc Harry]

...However, it is true that you have to manage your buoyancy, to blow a full breath into a bag and control it before release...

That's the tough part!....

 

[sambolino44]

I did it once by inflating the SMB with air I released from my BC. Same concept, basically. It wasn't real easy, but it wasn't that hard, either, to maintain a reasonable facsimile of buoyancy control.