TDI Decompression Procedures question

[decompression]

I believe that the usage of lift bag is a generic term that includes SMBs. When I started tech diving I had never heard the expression SMB but used a lift bag to assist in staged ascent.

Dave, when you started there weren't even row boats!

 

[wedivebc]

Dave, when you started there weren't even row boats!

C'mon Jay I'll bet you've been diving as long as me or more.
Fortunately tech diving hasn't been around all that long so it is one field where it isn't that hard to be an old timer.
So the big question, have you ever used a Jersey reel with your lift bag?

 

[Jax]

:lol:

Awesome!!

that one makes sense to me

It's an even better SMB - 7', orally inflate on the surface, and it sticks straight up. If you have a weight belt, put it through the straps to hold it upright. If you have an Intova light, like the ultra nova, on a clip on your gear, you put the light in strobe mode, shove it in the bottom where you inflate with reg, and clip it to the small d-ring at the opening. Makes your bag flash like a neon light!

 

[Hawkwood]

Hard to find a SMB with 25lbs of lift

It's not hard:

https://www.diversalertnetwork.org/store/home.aspx?id=5

 

[Akimbo]

So, how would you execute such an ascent? Release gas from lift bag by tilting the bag sideways or monkey with the OPV? ...

If you have a spool or reel with enough line, just shoot it and climb. Without a reel, you have to get enough air in the bag to help lift you off the bottom. Limit the volume by keeping it partially rolled. Let expanding gas go through the OVP or open bottom on a lift bag.

Limiting the volume to less than is required, but enough to allow swimming up, reduces the risk of losing control. You don’t have enough time or hands to stop the parade once it gets too full. Be ready to let go and drop lead in case it does.

I have no idea if this is a TDI sanctioned technique, but it worked for me.

 

[decompression]

There was a time when I had my students use improvised lift bags (garbage bags) and improvised OPV's (knives), gives a whole new appreciation for boyles law.

 

[Dr. Lecter]

Hard to find a SMB with 25lbs of lift

Huh? Lift Devices Comparison | Halcyon

 

[mrboab]

I do actually dive with a 50lb lift bag as a back up SMB/DSMB when using twinset and i feel more safe having a way to ascend in case of a wing's problem (even using a double bladder)

 

[Doppler]

So, how would you execute such an ascent? Release gas from lift bag by tilting the bag sideways or monkey with the OPV? God help me if I am ever in that predicament.

No, you send the bag up to the surface and use your reel or spool to help overcome the "slight" effects of gravity to get your arse up the water column.

Diving anything close to a so-called balanced rig there is little to compensate for -- some folks maintain you should be able to swim your rig up -- but hanging from a DSMB (to give the device its correct name) allows one to hold a stop without swimming like a moron.

The OLD SCHOOL technique of riding a bag to the surface is fine for an NDL dive... and something that it's fun to try with instructor candidates (a dump valve is essential), but as a common practice, this skill went out with breathing from a cylinder valve with no regulator on. Not something sanctioned in standards... but fun to try.