DSMB is flaccid upon deployment. Looking for tips.

[Tigerpaw]

So today I am practicing deploying my DSMB. A few months ago in the ocean I had great success. I realize that it is a skill that needs to be practiced so I set aside some time to do so today. I was at a lake at 20ft. I unrolled the sausage and used the inflator to manually inflate it. I then held the spool and it shot up. After it stopped moving I tied it off and then at the end of my dive I surfaced. (I did the deployment at the beginning of the dive. After deployment I swam around and the surfaced) When I surfaced about 2ft of sausage was above water, the rest was just under the surface and folded.

So on my next dive I put in more air (using lungs) this time when I surfaced half of it was sticking out the water. I then submerged and tried to reel it in but couldn't as the buoyancy was pulling me up. I had to swim up to the DSMB and roll it from the top.

I tried different things but I can't the DSMB to fully inflate out of the water. I do have an overpressure valve so should I inflate it more? I only gave it two puffs because I learned that air expands but in this case it didn't expand enough.

Any help or advice is appreciated. Thanks!

 

[inquis]

As you probably suspected, there's no magic here. Either add more air or deploy from deeper. From 20 ft, you need to fill it 63% full (from the top) for expansion to finish the job. (=surface pressure/pressure at depth).

Some will even draw a line on the DSMB with a marker at various distances from the top and write minimum depths (halfway from the top labeled 33 ft, etc).

 

[TrimixToo]

Viagra?

OK, sorry, not helpful (but I couldn't help myself).

The problem with full inflation is one of retaining the SMB or bag without losing buoyancy control. If you are on the bottom, a wreck, or a line, you can dump gas from your wing to stay negative up to a point and/or hang to something as you inflate the SMB or bag fully and let it go without it dragging you up. If you're in the water column, it's harder. You can let air out of your wing to a point but then there is only so much gas in your wing, and there is also a maximum inflation rate involved so you'll go down somewhat once you let it go. Life is full of compromises and this is one of them. As pointed out above, it's easier to have full inflation on the surface the deeper you are.

 

[Marie13]

OP, limp might be better word for your title.

 

[The Chairman]

Viagra?

Beat me to it. Start deeper is my answer. (Yet another double entendre!)

 

[Superlyte27]

A bolt snap is the key.

 

[OMyMyOHellYes]

A bolt snap is the key.

Sounds painful.

 

[Divin'Papaw]

So today I am practicing deploying my DSMB. A few months ago in the ocean I had great success. I realize that it is a skill that needs to be practiced so I set aside some time to do so today. I was at a lake at 20ft. I unrolled the sausage and used the inflator to manually inflate it. I then held the spool and it shot up. After it stopped moving I tied it off and then at the end of my dive I surfaced. (I did the deployment at the beginning of the dive. After deployment I swam around and the surfaced) When I surfaced about 2ft of sausage was above water, the rest was just under the surface and folded.

So on my next dive I put in more air (using lungs) this time when I surfaced half of it was sticking out the water. I then submerged and tried to reel it in but couldn't as the buoyancy was pulling me up. I had to swim up to the DSMB and roll it from the top.

I tried different things but I can't the DSMB to fully inflate out of the water. I do have an overpressure valve so should I inflate it more? I only gave it two puffs because I learned that air expands but in this case it didn't expand enough.

Any help or advice is appreciated. Thanks!

1. Shoot it deeper and let physics do the work.
2. Sounds like you are orally inflating it? Regardless, let some air out of your BCD so that when you exhale into the DSMB, you are still neutral. That allows you to do a second solid breath.
3. Use a second BCD hose or drysuit hose to power inflate it. I have a separate BCD hose on my pony bottle for the sole purpose of inflating my DSMB.

Using a combination of the above, it will soon be rock hard on the surface.

 

[Superlyte27]

1. Shoot it deeper and let physics do the work.
2. Sounds like you are orally inflating it? Regardless, let some air out of your BCD so that when you exhale into the DSMB, you are still neutral. That allows you to do a second solid breath.

Or use a Bolt Snap

 

[Tigerpaw]

As you probably suspected, there's no magic here. Either add more air or deploy from deeper. From 20 ft, you need to fill it 63% full (from the top) for expansion to finish the job. (=surface pressure/pressure at depth).

Some will even draw a line on the DSMB with a marker at various distances from the top and write minimum depths (halfway from the top labeled 33 ft, etc).

Thanks for the formula, so whatever value you come up with is the percentage that the DSMB needs to be filled. At 40ft it's 46%. Gonna give it a try.