SMB: weighted or not?

[elmo]

When launching an SMB from a decent depth to use as an upline, I was taught to fill the smb (open bottom) with vented exhaust from the wing. The idea is that your overall buoyancy doesn't change while you fill it (until you let the smb start to ascend.) You can always adjust your wing inflation after the smb launch has settled down.

Why not inflate orally or using reg exhaust? Buoyancy also remains constant while inflating, but unlike dumping air from your bc, you don't need to compensate once you release it. Just breathe in.

In response to the original question. I cut the lead out of my smbs. And I would do it again.

 

[CPRC]

All, thanks for these responses and helping me decide about an SMB with weights. Good insights from more experienced folk.

 

[decompression]

Jesus Christ................another f*&ken course that covers stuff that should have been included with basic training. What's next..... a course on which bootie you put on first?
John

Yes, it should be and is......now for all those that don’t have this essential training is it “too bad, so sad”?

 

[decompression]

When launching an SMB from a decent depth to use as an upline, I was taught to fill the smb (open bottom) with vented exhaust from the wing. The idea is that your overall buoyancy doesn't change while you fill it (until you let the smb start to ascend.) You can always adjust your wing inflation after the smb launch has settled down.

I’m really against this........to be done safely your hands are already busy with the bag and the spool (entanglement), so it’s far easier just to use your exhaust from your breath than inflate/deflate your BCD while holding the bag and the spool. Using your breathe just transfers the buoyancy from your lungs to the bag so zero change in buoyancy. Now if a second or third breath is required a simple downward kick will keep you stationary long enough to launch the bag.

 

[admikar]

Some of the SMBs with a nozzle to take a LP inflator hose can get clipped to the fitting. It isn't just a simple tube, but they have the recesses for clipping on.

Unfortunately I have witnessed a sealed SMB rupture when overfilled. Tends to happen on the smaller, narrower SMBs which are easily overfilled. It could never happen to an open bottom traditional SMB.

YMMV

I have a 4 foot DSMB with OPV, with what I think is called duck valve. I inflated it orally to full and put it upright under me and sit on it, so I can check that OPV. No way it could burst.

When launching an SMB from a decent depth to use as an upline, I was taught to fill the smb (open bottom) with vented exhaust from the wing. The idea is that your overall buoyancy doesn't change while you fill it (until you let the smb start to ascend.) You can always adjust your wing inflation after the smb launch has settled down.

How I use my DSMB: spool held by middle and thumb, point finger hooked to DSMB "connection line" (not sure how to call this). Stuck my 2nd stage at the bottom and purge, exhaling until I just unhook finger and let it up. Second stage in my mouth, inhale, buoyancy swing of no more than 50 cm, if that. Of course, easier at greater depths, but never had one launch under-filled.

 

[ERRN]

I've gone through a couple of different style SMB's over the last few years due to breakage, loss, gifting etc... I personally would agree with the idea to forget a weighted SMB if it is going to be shot at depth. I personally don't like the idea of disconnecting my BCD hose to push it into the nipple on the SMB at all. And honestly orally inflating at depth seems needlessly messy and complicating, not saying people don't do it, but I've never seen it done FWIW. I prefer the open bottom with baffle SMB. I can fill them with either my exhales from primary reg, or by purging my secondary reg into it. By using the exhale from my primary I have both hands free to handle the SMB and reel, or one free to purge my BCD if needed. I have seen a number of divers flail around using the LP BCD hose attachment to fill. While I am sure that with practice it gets easier, my thought is anything that minimizes the tasks I have to do is better. For me , one hand to the left side of the SMB holding it open, one hand on the right (also holding the open center of the reel between 2 fingers) large exhale and let go is both easy, safe and simple. No need for weight since you are taking up the slack on your reel as you ascend and can keep it as tight and upright as you need to by staying a bit negatively buoyant if you want.