Lift Bag V Smb

[DevonDiver]

In your opinion is it better to orally inflate or attach to LP inflator?

IMHO, the LP inflation is primarily an option for rebreather divers. Oral inflation is a bad option for them, as it means losing gas from the loop.

For OC divers, oral inflation works great; especially when the DSMB is launched from a depth where air expansion will do the hard work for you. Put a single breath into the DSMB and you're simply transferring buoyancy from your lungs to the bag. Release the bag before you inhale again. That way there's no positive buoyancy or deviation in your depth.
It will depend on the size/volume of your DSMB, but a quick visual check will determine how full the DSMB is from a single breath. Use physics to do that hard work for you. For instance, if a single breath half-fills the DSMB, release it from deeper than 10m (2ata) so it will be full at the surface. If only 1/4 full from a single breath, release the DSMB from 30m/4ata to ensure sufficient gas volume by time it reaches the surface.

My method for deploying an oral-inflation DSMB (with spool, not reel) is:

1. Keep the spool, bolt-snap (if used to connect) and oral-inflate tube in the right hand. The tube (and boltsnap) secured under the thumb, with forefinger as axel to the spool (knuckle bent). The means it's all controlled one-handed, with no dangling line.

2. Inhale a normal breath and, with the left hand, remove the regulator from your mouth.

3. Exhale into the DSMB tube.

4. Hold the reel/DSMB away at arms length, check above you, then release.

5. Maintain friction/control on the spool using your thumb.

6. Re-insert the regulator with your left hand and continue breathing.

(I will try and get photos of this process at the weekend).

 

[boulderjohn]

Yes, deco hangs have traditionally been done neutrally buoyant, but there can be a good reason not to do so. If you are using a SMB, hanging onto the line while negatively buoyant will keep it upright on the surface.

 

[Veritably337]

Devon thanks I'd like to see that.

 

[rjack321]

Yes, deco hangs have traditionally been done neutrally buoyant, but there can be a good reason not to do so. If you are using a SMB, hanging onto the line while negatively buoyant will keep it upright on the surface.

If the current is really ripping the only way to stay under the bag is to "hang" on it too. Directly under may or may not matter that much depending on the site/dive.
Also if you or a buddy has a major problem, buoyancy may very well go to hell. In which case get the problem diver to hang on the SMB more instead of yo-yoing all over the place. A buddy of mine had a disorienting inner ear problem on deco once. I put her on the line and put my hand over hers so she knew I was "there" and relatively stable. As I recall her eyes were closed and she was massively dizzy. Being a few pounds heavy on the line and at a stable depth we waited together for her symptoms to resolve. Thankfully it wasn't an inner ear hit and we surfaced maybe 15mins later no worse for wear.

 

[Michael Guerrero]

Not sure if anyone posted this cuz I just skipped to the end, but sort of what AJ said. I have an SMB in my pocket, already rigged to a spool so that I can shoot the buoy to do a free ascent if needed and let boats know I'm coming up. I also keep a lift bag (50lbs though, 100lbs is crazy big and unnecessary bulk) bungeed to my backplate for redundant buoyancy. So...both?

 

[Reku]

I carry 2 of each.

 

[MattCain]

I personally carry the 3 foot halcyon smb (oral inflate) pre rigged to a 150ft finger spool in my pocket. I also keep a halcyon 6 foot smb in my backplate in case I need to get the boats attention if they don't see my 3 foot one, but the 6 foot one also doubles as a lift bag if necessary. Last week I totally flooded a gavin scooter at a 20 foot deco stop and my buddy attached his halcyon 4.5 foot lift bag to it to send it to the surface. While this was not the intended purpose for the smb, it brought my totally flooded gavin, which was quite negative by the time we sent it up, safely to the surface with plenty of lift to spare. The advantage of a big smb over a lift bag is its better than a lift bag to get the boats attention if your lost at sea.