OPV on DSMB ?

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JohnN

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I have a 6' (Piranha mfg.) closed bottom DSMB, but it does not have an OPV.

I've never tried shooting it below 30', but at that depth and shallower, I'm unable to blow enough air into it to get close to over expansion.

Is this a problem waiting to happen? I like the longer length (just in case I really need to get spotted on the surface), but I'm cheap by nature and can't find an alternative reasonably priced 6' DSMB

DSMB is here: http://www.piranhadivemfg.com/item/Closed-Bottom-6ft-ORANGE-SMB-2996
 
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Closed bottom SMB without an OPV? Never heard of that. You're probably not going to pop a 6' buoy from recreational depths unless you jack it into an LP hose, though.
 
If there is no opv then it's just for surface deployment, not from depth.


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When the dive is over and you are safely on the boat, how do you release the air from inside the SMB?

My guess is that whatever mechanism it has for releasing the air is also an OPV.
 
Now seems like a good time for the uninformed to ask: What is the advantage of a closed-bottom SMB over an open-bottom SMB? You can deploy an open-bottom SMB either at depth or (perhaps slightly less easily?) on the surface.
 
Now seems like a good time for the uninformed to ask: What is the advantage of a closed-bottom SMB over an open-bottom SMB? You can deploy an open-bottom SMB either at depth or (perhaps slightly less easily?) on the surface.

Cost is one I've found but it wasn't significant enough for me to consider it, personally. I have no actual experience with a closed-bottom SMB, though, so I'll be interested in seeing if anyone has another advantage.
 
Now seems like a good time for the uninformed to ask: What is the advantage of a closed-bottom SMB over an open-bottom SMB? You can deploy an open-bottom SMB either at depth or (perhaps slightly less easily?) on the surface.

Open bottom can be filled a couple of ways and can release air if overfilled while ascending, disadvantage is air can spill at the surface making the smb useless.

For a closed bottom with no opv, the inflator is also the deflator. Again, really only meant for surface use.

I have about a dozen SMB's for several different applications, I like to show my students a wide variety and their uses.

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I've only been lost at sea one time, for about 20 minutes. The waves were pretty high and I was glad my SMB was closed bottom. I had enough trouble trying to keep it upright in the wind that I believe an open bottom one would have lost air and not been able to be kept as stiff, and it needed to be stiff to show. If it was only for shooting from below the surface then I would only want an open bottom one, but its not.
 
https://www.shearwater.com/products/perdix-ai/

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