Lift bag as backup lift device: open bottom or baffled?

[CPRC]

I want to get a dedicated backup lift device in case of bc failure. I have recently taken DP/AN classes, have tried only dsmb's as part of my training and practice afterwords. And I can see the advantage to carrying some kind of device that is a bit more robust/has more lifta (not just a skinny dsmb I've been using). I do not plan on lifting junk off the bottom. But I'm struggling to understand the advantage of one type of design vs the other. For instance, I've read that, when shot to the surface the open bottom type are easier to fill but they flop over then the gas spills out, but with a bottom baffled unit it's difficult to deflate when at surface when one wants it to be quick about it, there is nothing quick about that type. What do divers prefer and why?

 

[inquis]

Semi-closed / baffled DSMB should have an exhaust valve. Deflates very quickly. The larger ones have about 40 lbs of lift.

 

[CPRC]

Yes, always have OPV.
What are tech divers using? Which brands / style?

 

[OTF]

I had one "duckbill" baffle style open-bottom DSMB, made by Manta so super tough construction and I assume top of the line all around. Inflating it by purging a reg or even exhaling exhaust bubbles into it was super easy, lots of air went into it fast. But if it was deployed for any extended period of time it tended to collect quite a bit of water inside. And that water was annoying to completely drain because the baffle prevented it from flowing to the dump valve.

So I've given up on open bottom/baffle types and use the sealed/closed bottom type exclusively. No issues with them. Bigger is better, I use the six footers. Think about what you would want to have if you were adrift for hours.

Your mileage may vary.

 

[Thrutch]

If you're considering using it as backup lift, you definitely want a closed bag. I use the Mares XR that DGX carries. It's got 80 lbs / 36 kg of lift. Really nice to hang on for stops. OPV deflates it just fine at the surface.

 

[rongoodman]

If I’m someplace where I want a big bag, such as Cocos Island, I carry one of the Halcyon Super Slim 6’ bags. If I’m taking it I also have a 26” inflator hose with a DiveAlert clipped to my left side D-ring, which gives me room to hold the SMB well away from me while inflating it.

 

[NW Dive Dawg]

I personally think that using a lift back as your "planned" back-up for a failed BC is not a good plan....... Your backup for a failed BC should be your fins.....combined with proper weighting...

But...... having said that... I get the concept and believe folks should make their own choices. For overall control when lifting anchors, I prefer the baffled lift bags with the OPV at the top and a manual pull / dump cord that's at the bottom of the bag.

For back-up buoyancy in case of BC failure on the surface, I think an SMB is a more compact and better option.

 

[Lorenzoid]

I personally think that using a lift back as your "planned" back-up for a failed BC is not a good plan....... Your backup for a failed BC should be your fins.....combined with proper weighting...

Swimming up should be possible, but a lift bag can be used for buoyancy after surfacing. Even a drysuit doesn't work so well for that. I'm not really an open ocean diver, but I would have a drysuit and probably also carry a lift bag for inflating on the surface.

 

[OTF]

Sorry in my earlier post I missed that this was specifically asking about DSMBs for backup buoyancy. You DEFINITELY want a fully closed DSMB for that. You don't want to pour air into it rapidly like an open bottom allows, but rather to slowly orally inflate it while riding it like a pool noodle and dumping excess air as it expands so that you can control a safe ascent rate.

Practice this before you need to do it in an emergency.

 

[GF99/99]

I have tried tons and tons of SMB's over the years and probably spent more on SMB's than some spend on there who singe tank kit. Halcyon, Mares, Xdeep, SP, DGX, generic brands, etc. etc. The best SMB's I have come across are the AP one's AP Self-sealing SMB Surface Marker Buoy

I spend ALOT of hours hanging from SMB's on deco. Lots of my typical dives are 4-6hr run times and the AP ones last the longest, are user friendly, and are big.

The only downside is I have never found them for sale in the US so I always end up getting them out of the EU/UK

For emergency use they are great also. I remember years ago when I did my Adv. mix gas course my instructor made me do a loss of buoyance drill with 4 S80 BO on and a JJ with 3 onboard tanks strapped to my back. The drill was fully deflate wing, to simulate my wing popping, go vertical and start kicking like a made man so you don't sink like an anchor while trying to fumble around and find you SMB, start inflating it (but not over inflate it where you get dragged to the surface) Then I had to ride the SMB up and complete all my deco stop from the SMB. This was all done from 70m All while my instructor kept trying to dump my wing to ensure there was no gas in it. So I can confirm that an AP SMB will support a diver with a fully built JJ (close to one of the heaviest units on the market) and 4 full S80's with 1st stages.