SMB: weighted or not?

[Random Dude]

Owns a smaller (45’’x 5’') open ended SMB with flexible weights, noticed that the weights seem to at least delay air running out when the SMB flops over, making it a tad forgiving (in my opinion). Concur that the weights don't help in pulling the SMB upright at all.

 

[Random Dude]

Noticed that they are generally not useful in erecting the SMB, but nice to have in a open ended SMB, as I noticed that it tends to keep the air in for a while more when the SMB flops over, thus being more forgiving. My SMB is a small one, 45’’x 5’' though, with flexible, malleable weights at the bottom.

 

[stuartv]

Stop blowing it up orally.

If you use a drysuit pull of the lpi hose and fill it up. If you don't disconnect the lpi from your bcd and fill it up. If you are nice and neutral when you do this then it won't cause you any problems. And even if your buoyancy is a bit dodgy - you can use the smb to hold yourself.

You might not get away with this on some courses with some instructors. But it will make life an awful lot nicer for you generally when diving. Once you start diving in nasty conditions and using big boy smb's then it's what you will have to do anyway.

I guess I haven't gotten there yet. :-(

Normally, I just tilt my head to the side and let exhaust from my 2nd stage go into the SMB. From depth, that normally gives it plenty of "fill" to be full when it gets to the surface. If I'm putting gas into something bigger, like a lift bag, I will switch to my short hose reg (for breathing) and hold the long hose 2nd stage under the SMB opening and purge it for a second or two.

Never needed (or wanted) to hassle with disconnecting my LPI. Besides, my LPI hoses are all short, so they don't come very far over my left shoulder. Trying to connect it to an SMB inflator would be very annoying, I think.

If the water were too cold to risk purging a 2nd stage and starting a freeflow, and I needed enough gas to fill a lift bag, I might figure out a different plan. For normal, recreational diving, this has not been a concern for me, so far.

 

[Umuntu]

I am shopping for my first SMB. Many are weighted, others are not. Are the weights truly effective at helping keep the buoy erect at surface while attached to one's line or is the effect negligible and a waste?

More important to get one that is sealed. With the open bottom type the air empties out at the surface and it just flops over with a little air keeping a strip of red plastic on the surface. Not really visible to anyone.

I like to add a weight to the bottom. Tied as close to the plastic as possible so that it holds the SMB in the water. If there is any length of string between the weight and the SMB the SMB will still flop over on the surface. Pulling it down helps.

How much weight. 1kg displaces 1 litre of fresh water. A little less of salt water. So it depends on the thickness of your SMB and how much of it you want to stay in the water.

Safe diving !

 

[decompression]

This is one of the reasons that there are SMB training classes (PADI, UTD et al). There are so many different SMBs, different techniques and different usages that many divers don't really think about it.

Stuart, there is a nifty device called a qwik shot, I have one on one of my deco regs, super easy to inflate.....

 

[shoredivr]

I have an extra inflator hose on my deco reg to inflate my SMB through the inflator, though on a non-deco dive I use the "tilt my head to the side, exhale into the bottom of the SMB" style mentioned above.

The SMB I'm currently using has an inflator plus a bottom inflating option with a baffle to prevent it from leaking air at the surface, and two small lead strips on each side of the bottom self-sealing one way opening that holds it open slightly: you pull the bottom open and the lead strips hold it that way while you exhale into it. I don't think the lead is there to weight the SMB, and pulling on it is sufficient to keep it upright.

 

[stuartv]

Stuart, there is a nifty device called a qwik shot, I have one on one of my deco regs, super easy to inflate.....

Pretty cool. But, apparently, discontinued. Anyway, for something like that, I might just put on a LPI hose. I can see where the quickshot might be a little easier, though.

Does it have any potential to freeze open when you use it in really cold water?

 

[Umuntu]

Pretty cool. But, apparently, discontinued. Anyway, for something like that, I might just put on a LPI hose. I can see where the quickshot might be a little easier, though.

Does it have any potential to freeze open when you use it in really cold water?

Also, using a LP hose to inflate a sealed SMB runs the risk of over-inflation and bursting the balloon There should be an opv valve, but sometimes their isn't or it can't cope.

But if you have a BIG SMB and really like the idea of using a LP hose to fill it, consider having a dedicated LP hose, and remove the clip mechanism on the end so the LP hose doesn't stay attached to the SMB and drag you up during deployment.

 

[HantsDiver]

But if you have a BIG SMB and really like the idea of using a LP hose to fill it, consider having a dedicated LP hose, and remove the clip mechanism on the end so the LP hose doesn't stay attached to the SMB and drag you up during deployment.

No SMB will attach in that way. And if you have the faintest idea how to do this then there is no chance of being dragged to the surface. You have more chance with a traditional SMB if I'm honest.

I've never heard of the exploding SMB's. I'm not convinced this is a real problem...

 

[decompression]

Pretty cool. But, apparently, discontinued. Anyway, for something like that, I might just put on a LPI hose. I can see where the quickshot might be a little easier, though.

Does it have any potential to freeze open when you use it in really cold water?

Potential, probably but not so far in 45 deg water. That said, I don't use it often anymore as its now more of a demo when deploying a bag at a shallow deco stop for students.