Lift Bags for Emergency Ascend

[Freewillow]

Tec diver would rather go for a minimum of 40/50 lb DSMB.

 

[DevonDiver]

Different places and boats have different procedures

I really never fathomed why the rest of the world never took up on the simple protocol of yellow/orange DSMBs as is commonly used around Europe.

Orange DSMB = All is well, I am ascending.
Yellow DSMB = Emergency at depth, send help/gas.

Liftbags are for lifting stuff.... unless you learned to dive in the 1970s.... and stopped learning thereafter.

 

[Freewillow]

Wel Devondiverl, you never noticed that any country, that has English as their native language, have their own rules: imperial versus decimal / DSMB Colors / Red and Green buoys inverted for port entrances...............

How, I forgot to mention: they also have weirdoes politicians such as Boris Johnson and Donald Trump .

 

[Subcooled]

Tec diver would rather go for a minimum of 40/50 lb DSMB.

Why?

 

[Freewillow]

Why?

Well, at least this is what I have been told frOm my IANTD course: minimum gear, 2 first stages on two separate tank exits that can be independantly closed, long house for primary second stage and back-up second stage around the neck with a bungie + DSMB of a minimum of 20 Liters - so 45 Lb).

The reason is that you are supposed to lauch it from depth 70 feet and lower - so inflation is not an issue - and use it during your deco stops. If you want to hang negatively on the line and you wish to have your SMB clearly visible by the surface watch, a certain volume seems mandatory to me.

 

[Subcooled]

If (...) you wish to have your SMB clearly visible by the surface watch, a certain volume seems mandatory to me.

This is a valid reason.

 

[dberry]

Wow are you actually suggesting using an SMB as a buoyancy device during ascend? WHY?

What's the advantage of not just letting go of the SMB when you deploy it? I would always deploy an SMB when I'm a stable platform. This could be at the bottom, to release the smb and tie of to the wreck so I stay "attached" to the wreck during ascend, or at a specific depht (for example when you slow the ascend to minutes per 3m or when you make a gas switch) during a free drifting ascend; This way you arrive at that depth, stabilise yourself, and then deploy an SMB.

There is nothing hard to it, in fact it's very easy. Your method seems to me quite hard and has no benefits. You need to manage another bubble (next to your wing and drysuit) which is unnecessary and you are handling a partially inflated smb "pulling" you up while ascending which seems a bit risky. Care to go into detail about what the benefits of this approach would be?

This is something I was taught to do in a recent wreck/ deco procedures course, and I believe it's a required skill in the TDI manual. We did two dives a day for 5 days, and the second dive each day ended with practicing deploying the SMB for a controlled ascent to the first deco stop. It seemed pretty easy and safe if performed as I tried to describe it. If you imagined we were being dragged up by the SMB , I did a poor job describing it.

Again, the skill was for open water ascents without a fixed line. We were not given the option of tying off to the wreck for ascents. Deploying an SMB from 140' directly to the surface doesn't seem much easier than what we learned to do. If nothing else reeling in 70' of line on the way to a stop at 70' seems like a lot of work. Also, if there is any current won't you have to play out (and reel in) a lot more line for the SMB to reach the surface?

By partially filling the smb with air from the bc (and holding on to it), you haven't changed your buoyancy at depth. The SMB floats a little above your head, with little or no line played out. Once we starting ascending it didn't seem very hard to maintain a proper rate, and the dive profiles from my computers seem to bear that out. Managing the bubble was little more than venting some gas every so often, and staying a bit heavy on the SMB. Letting it play out as we began to approach the stop didn't seem that much harder than launching it from a fixed depth. Did I hit every the first stop at exactly the right depth +/- 1 foot? No, not every time - hey, I'm new at this!

But I'm still learning, and am open to different ways to do things.
-Don

 

[Freewillow]

By partially filling the smb with air from the bc (and holding on to it), you haven't changed your buoyancy at depth. The SMB floats a little above your head, with little or no line played out. Once we starting ascending it didn't seem very hard to maintain a proper rate, and the dive profiles from my computers seem to bear that out. Managing the bubble was little more than venting some gas every so often, and staying a bit heavy on the SMB. Letting it play out as we began to approach the stop didn't seem that much harder than launching it from a fixed depth. Did I hit every the first stop at exactly the right depth +/- 1 foot? No, not every time - hey, I'm new at this!

But I'm still learning, and am open to different ways to do things.
-Don

Interesting exercice.

Just two questions/remarks:

1. If you are correctly weighted, at the time you want to ascend, you sould have CLOSE TO ZERO air in your BCD. If you have neutral buyancy - as few divers do - you practically do not need to add air to your BCD in order to start the ascend. So were/how do you transfer air from your BCD to your DSMB?

2. While you are going up, I understand that you are supposed to let some air go from your DSMB. Why would it be easier to release air from an DSMB if you are used to manage air release from your BCD?

The way I mostly do it - and have been taught - is that I go up and once I reach +/- 60 feet or sometimes twice the depth of my safety/deco stop, I launch my DSMB.

 

[rongoodman]

Interesting exercice.

Just two questions/remarks:

1. If you are correctly weighted, at the time you want to ascend, you sould have CLOSE TO ZERO air in your BCD. If you have neutral buyancy - as few divers do - you practically do not need to add air to your BCD in order to start the ascend. So were/how do you transfer air from your BCD to your DSMB?

I don't understand the point of the TDI exercise either(why not just shoot the bag from the 70' stop?), but this was presented in a tech course, so between deco gas and required reserves of back gas the diver is never going to have an empty wing, unless there's a big problem.

 

[Freewillow]

I don't understand the point of the TDI exercise either(why not just shoot the bag from the 70' stop?), but this was presented in a tech course, so between deco gas and required reserves of back gas the diver is never going to have an empty wing, unless there's a big problem.

I get you, and agree for heavy duty deep tech dives maybe.

I just consider the question of the Op, 20-50 Dives as experience and talking about emergency (?) ascent with a SMB or a lift bag.