DSMB Technique

[Gelirfella]

Working on dialing in DSMB inflation. Have a 6ft. Still sometimes losing buoyancy control significantly while inflating it. Practicing right generally at 15 feet while on a safety stop. I’ve been told that theoretically my buoyancy doesn’t change as long as I don’t inhale again but practically speaking it does. That said, it’s probably just that my buoyancy would have changed to the same degree if I’d taken a big inhalation and held it. Same amount of air I guess regardless. Do I need to adjust my buoyancy from neutral to a little negative prior to inflating to prevent this? (Ie should I make it such that i would be neutral after a big inhalation rather than neutral around tidal volume?)

Also, one big breath doesn’t fully inflate a 6 foot. Probably need 2 or 3. This is a non issue if I were in a more realistic situation and floating it from 30 feet or so given the expansion, but is it worth practicing full inflation at a shallower depth? Probably will have to become progressively more negative with each breath right? in order to maintain depth? So the sequence is basically inflate with one breath, dump wing, inflate again, dump, etc until Smb is full then release and restore neutral buoyancy while holding the reel?

I practiced this skill in open water but not with any rigor.

 

[Doc]

I guess I cheat.

I inflate my monster OMS tube with my octopus, I ask a friend to maintain buoyancy at 20 feet - I gauge my depth off of him.

I start the process a titch negative (2#?) so i am doing a minor bit of finning. Better to sink 4’ than pop up.

I inflate the sausage and let it fly with a 30 foot length of 550 cord on it. Seems to work OK for me.

/END BLASPHEMY

A lot of people practice this only once per each dive it’s really better to find a 30 foot depth or whatever you want to use and do it for 45 minutes or an hour ….until you get it right.

that many people do not bother to do this …that’s the only way to get it …keep practicing.

Most students I’ve had find more difficulty in not strangling themselves in the tether line, rather than losing buoyancy.

Repetition.

 

[inquis]

should I make it such that i would be neutral after a big inhalation rather than neutral around tidal volume?)

That's what I do, even before getting the DSMB out.

 

[inquis]

Probably will have to become progressively more negative with each breath

At some point, your wing will be empty and you will be unable to become more negative. I think it's best to just deploy from deeper.

 

[Angelo Farina]

I also use the secondary regulator. I first fully inhale for having maximum buoyanvy and release air from the BCD, so I am neitral with full lungs.
While I inflate the buoy with the octo, I exhale, so that to remain neutral.
When the buoy is almost full, I release it, inhaling again, and I am back to neutral. Finally I exhale gently while filling the BCD.

 

[Edward3c]

When we (BSAC) teach DSMB it’s from the bottom at 10-20m, once proficient we move to mid-water deployment. All whilst horizontal.

Core skill for Advanced Ocean Diver – 10-20m deployment.
Local conditions for Dive Leaders – 10m mid-water deployment.

 

[Fishdip]

I use a extra inflator hose… as far as depth change try doing something very distracting like math on wet notes and see if you still have the same issue with depth change if you do then you need more practice with buoyancy and being a little neg to launch a SMB is just covering it up.

 

[Nemrod]

You might start with a DSMB of 44 to 48 inches. I prefer the close bottom type with an OP valve. I can usually get enough air in it with one breath from 20 feet. I also use a Y fitting sometimes to inflate from my BC LP hose, especially the jumbo DSMBs:





The DSMB should have a non-locking inflator:



I stick it in the fitting, psssst, zoom, up, up and away.

Unfortunately, I have not seen those fittings in years though there are some that are reverse of it that would likely work as well or better.

 

[Raphus]

I use my dry suit inflator. It's fast, so being bouyant is not a big problem. But it needs to be practiced.. it's easy to shoot yourself up, if done wrong

 

[Wibble]

I use my dry suit inflator. It's fast, so being bouyant is not a big problem. But it needs to be practiced.. it's easy to shoot yourself up, if done wrong

Worse still is a flaccid blob on the surface!