Failure to Deploy... SMB Problem

[SeaHawk12]

What could of happened us when you forced the air out of the SMB on you SI, you may have trapped a thin layer of water between the sides of the SMB, effectively sealing it. Just a thought.

 

[maniago]

Ahhh, young grasshopper, you will learn that in the quarry. Wax on, wax off. The nearer you are to the surface, the more the SMB expands with the air you put in it. As the SMB expands, it exerts positive buoyancy on you, dragging you to the surface. It's way easier to shoot a bag from depth, because as the bag rise, the air in the bag expands, so when it hits the surface, it is fully inflated. If you are already near the surface, the bag (the air in the bag) doesn't have as much time (many atmospheres) to expand before you have to let it go. It is very difficult to inflate your SMB while dumping your BC/Wing then when you let the SMB go, re-inflate your wing to attain neutral or slightly heavy buoyancy.

That's why properly inflating a bag is a difficult skill.

Holy gas volume Batman, say it isn't so!

Dude, I totally get the expanding gas volume upon ascent, and the drag on the line that I need to be careful about. That doesn't answer my question. Why can't I rely on the blast valve to do its job? Else what is it there for?

 

[MrChen]

What could of happened us when you forced the air out of the SMB on you SI, you may have trapped a thin layer of water between the sides of the SMB, effectively sealing it. Just a thought.

Kind of what I figured. Scarey thing is it must not take much to seal it.

Sent from my Kindle Fire using Tapatalk 2

 

[windapp]

Ahhh, young grasshopper, you will learn that in the quarry. Wax on, wax off. The nearer you are to the surface, the more the SMB expands with the air you put in it. As the SMB expands, it exerts positive buoyancy on you, dragging you to the surface. It's way easier to shoot a bag from depth, because as the bag rise, the air in the bag expands, so when it hits the surface, it is fully inflated. If you are already near the surface, the bag (the air in the bag) doesn't have as much time (many atmospheres) to expand before you have to let it go. It is very difficult to inflate your SMB while dumping your BC/Wing then when you let the SMB go, re-inflate your wing to attain neutral or slightly heavy buoyancy.

That's why properly inflating a bag is a difficult skill.

huh? An SMB is not a rubber balloon. It doesn't expand. it fills up more or less with air. The amount of buoyant force the SMB exerts on you depends on how much you fill it. If you fill a 20L SMB 1/4 full, it will pull up with 5kg force (and yes, there is a such unit as kg force). As it rises, the air expands, and the SMB gets more full, so if you were to fill it to 1/4 full at 30 m, by the time it reached the surface, it would be 20 kg force buoyant. However, it would still pull up with 5kg force on you before you release it.

 

[idive2]

I started out with the open bottom type smb and guess I just never liked the flapper set up and didn't
really trust it all that well to stay inflated. I decided on the closed circuit smb and more confident in it staying
inflated. My first one was a 4.5 ft smb that really is a great size but came to find out that even getting it a quarter
full at 50 foot or so takes a few breathes. (reg out, blow in bag, reg in breath air, reg out blow in bag again...etc.)
I didn't like the idea of disconnecting the bc inflator and using it but did try it a couple times, just did not want to
fidget with getting it on and off. Now I have settled for a closed loop 3 foot Halcyon which does have the relief valve
unlike most other 3 foot safety sausages. I find the ease at which it fills when blowing into it, and deploying it much
simpler. It has no where near the surface area of the 4.5 ft smb but i guess everything is a trade off.

 

[Wookie]

huh? An SMB is not a rubber balloon. It doesn't expand. it fills up more or less with air. The amount of buoyant force the SMB exerts on you depends on how much you fill it. If you fill a 20L SMB 1/4 full, it will pull up with 5kg force (and yes, there is a such unit as kg force). As it rises, the air expands, and the SMB gets more full, so if you were to fill it to 1/4 full at 30 m, by the time it reached the surface, it would be 20 kg force buoyant. However, it would still pull up with 5kg force on you before you release it.

I'd be shocked if you can fill an SMB at depth without throwing your buoyancy off. Yes, the OP valve serves to vent off any excess expanding air as the SMB rises, but do you think you can fill a 20kg SMB while maintaining neutral buoyancy? If you fill an 20l SMB 1/4 full at 30m, it should be full at the surface. If you fill the same SMB 1/4 full at 10m, it would be 1/2 full at the surface, therefore you fail the skill. You would have to fill it 1/2 full, or have to overcome 10kg positive buoyancy pulling up from 10m to have it full at the surface.

That's why it's harder to properly shoot an SMB from a shallow depth.

 

[ajduplessis]

So I was doing my last 2 AOW dives.

Dive one, it's time to end the dive and start heading to our safety stop. I'm the only one on the dive with my instructor because I missed these dives due to getting sick. So he signals for me to deploy my sausage. I pull it out, grab my octo, put it under the smb, and away it goes. No problems whatsoever.

I get my wife to deploy my sausage She whips its out, grabs my octo and away it goes!!

Sorry, I just had too.

 

[MrChen]

I started out with the open bottom type smb and guess I just never liked the flapper set up and didn't
really trust it all that well to stay inflated. I decided on the closed circuit smb and more confident in it staying
inflated. My first one was a 4.5 ft smb that really is a great size but came to find out that even getting it a quarter
full at 50 foot or so takes a few breathes. (reg out, blow in bag, reg in breath air, reg out blow in bag again...etc.)
I didn't like the idea of disconnecting the bc inflator and using it but did try it a couple times, just did not want to
fidget with getting it on and off. Now I have settled for a closed loop 3 foot Halcyon which does have the relief valve
unlike most other 3 foot safety sausages. I find the ease at which it fills when blowing into it, and deploying it much
simpler. It has no where near the surface area of the 4.5 ft smb but i guess everything is a trade off.

I hear you about the connecting and disconnecting. I don't like disconnecting my octo unless I make a point to reconnect it prior to ascending. I left my octo hanging and I can see it getting banged up while getting back in the boat. If you disconnect your bc inflater, then inflate the smb, wait til it reaches the surface, then reconnect the hose. What if something goes wrong with the reel and reconnecting is just one more task you have in the moment. I'm considering adding another LP hose for inflating.

 

[windapp]

I'd be shocked if you can fill an SMB at depth without throwing your buoyancy off. Yes, the OP valve serves to vent off any excess expanding air as the SMB rises, but do you think you can fill a 20kg SMB while maintaining neutral buoyancy? If you fill an 20l SMB 1/4 full at 30m, it should be full at the surface. If you fill the same SMB 1/4 full at 10m, it would be 1/2 full at the surface, therefore you fail the skill. You would have to fill it 1/2 full, or have to overcome 10kg positive buoyancy pulling up from 10m to have it full at the surface.

That's why it's harder to properly shoot an SMB from a shallow depth.

But that is not what you said. I wasn't questioning that inflating an SMB is harder at shallower depth. I was questioning your explanation of the physics.

 

[Peter69_56]

You can buy an adapter for the inflation hose that has 2 connector ends in a Y, one for the inflator and one for inflating an SMB