First time DSMB

[Dive Right In Scuba.]

I spent part of yesterday on a dive boat watching DSMBs signalling divers doing decompression. They were using very big ones, and they were either bright yellow or orange. In my opinion, the yellow one was easier to see. The seas were a little rough, so having the high visibility was a plus.

What you want in a DSMB really depends upon the kind of diving you are going to do. The smaller ones are much easier to inflate and carry, and the larger ones are easier to see on the surface. If you are deploying it from depth, it is easier to fill because you don't need to get as much air in it to get the job done (because of expansion as it rises). There are a lot of choices, so give it some thought.

http://www.diverightinscuba.com/liftbagssmb-c-46.html

 

[cool_hardware52]

What you want in a DSMB really depends upon the kind of diving you are going to do. The smaller ones are much easier to inflate and carry, and the larger ones are easier to see on the surface. If you are deploying it from depth, it is easier to fill because you don't need to get as much air in it to get the job done (because of expansion as it rises). There are a lot of choices, so give it some thought.

A larger / taller SMB can be an advantage *IF* it arrives at the surface completely inflated, and *IF* the diver can keep it upright. A 6'ft SMB that's 1/2 full and requires 1/2 of the that 1/2 be pulled under water to keep it upright is less effective than a full 1 meter smb that has 90% of it out of the water.

If one launches any SMB from significant depth there is a good chance it will be full at the surface, much less so from shallow depth. Being able to fill a large SMB when shallow and maintain depth requires considerable practice and skill.

A large SMB can also require the diver be significantly negative in order to generate the force required to keep it up right.

What's easier to see? An upright 1 meter bag or a 1/2 full limp 2 meter bag lying on the surface?


Tobin

 

[decompression]

Is that an African or European smb? Monty Python......

 

[Freewillow]

Just make sure that your SMB keeps air at the surface. I had several ones that could not do it. Now, I have a "closed" SMB that can be inflated by mounth or with a LP line.

 

[Patoux01]

1. Doesn't matter, mine is orange, because it's fancy
2. I'd say 15m (whatever that would be in terms of body-parts is up to you)
3. Oral inflated (my opinion), gives a better control on buoyancy.
4. Depends on the diving done, but 1m to 1.5m is usually sufficient (my experience)
5. No. However when boat diving I typically carry a (closed) safety sausage as well, not really needed but well, I have it, and doesn't cause any issue to carry, so....


OPV is a need on a dsmb. DO NOT get one of those stupid open ones that are still sold in some places. Closed or semi-closed are fine.

Absolutely no need to find an instructor for this... Use some common sense and you'll be able to shoot it up perfectly in no time.

 

[Freewillow]

I agree with Patoux on this one

 

[Coztick]

If you dump air from your wing into the dsmb first, your buoyancy won't change and you can ensure you are sorted before releasing it at depth before ascending. Adjust buoyancy after a successful release.

 

[Peter69_56]

Anyone worked out the life of an DSMB. Mine is starting to leak. Fixed 6 and found another 3 this week. Its about 10 years old I guess. Becoming unreliable and not remaining inflated for 15-20 min deco time. Anyone else had issues over time?

 

[cool_hardware52]

Anyone worked out the life of an DSMB. Mine is starting to leak. Fixed 6 and found another 3 this week. Its about 10 years old I guess. Becoming unreliable and not remaining inflated for 15-20 min deco time. Anyone else had issues over time?

Like most dive gear "life" in years is not the best measure, use has a lot more influence. SMB's are made from fairly light weight fabrics, typically 200-400 denier nylons to which a thin film of urethane has been laminated using adhesive. This urethane film is what provides the airtight layer, and it is what is joined when the inflatable is "heat sealed" or RF welded.

Time alone will eventually stiffen the urethane, and UV exposure can fade the nylon textile, and degrade the adhesive bond between the urethane and fabric. Most "seam" leaks are the result of the urethane delaminating adjacent to a weld. The welding process effects the adhesive bond.

It's a bit counter intuitive, but thinner layers of urethane are more difficult to weld than thicker films, and "over sealing" is a real risk. The impacts of over sealing usually don't show up for years, making it very tricky for the manufacturer to tread the line between a good seal and over seal.

10 years of moderate use? I'd say that's more than I would expect, and the emergence of multiple leaks is a sure sign of the beginning of the end. You will be chasing delams from here on.

Tobin

 

[Peter69_56]

Like most dive gear "life" in years is not the best measure, use has a lot more influence. SMB's are made from fairly light weight fabrics, typically 200-400 denier nylons to which a thin film of urethane has been laminated using adhesive. This urethane film is what provides the airtight layer, and it is what is joined when the inflatable is "heat sealed" or RF welded.

Time alone will eventually stiffen the urethane, and UV exposure can fade the nylon textile, and degrade the adhesive bond between the urethane and fabric. Most "seam" leaks are the result of the urethane delaminating adjacent to a weld. The welding process effects the adhesive bond.

It's a bit counter intuitive, but thinner layers of urethane are more difficult to weld than thicker films, and "over sealing" is a real risk. The impacts of over sealing usually don't show up for years, making it very tricky for the manufacturer to tread the line between a good seal and over seal.

10 years of moderate use? I'd say that's more than I would expect, and the emergence of multiple leaks is a sure sign of the beginning of the end. You will be chasing delams from here on.

Tobin

Thanks Tobin. Thats what I thought was going on.

Sorty of like getting old isn't it