SMB, lift

jpitz31 · Dec 9, 2008

Hello All,

Been lurking for a while, decided I would join in.

Just finished my enriched air class. This week-end is deep and next week-end is wreck class.

I am thinking about getting a lift bag/SMB and was wondering what the proper procedure was for deploying the bag to the surface? Do you attach SMB to your reel and ascend while taking up the slack?

If you plan to use the SMB/Lift as an emergency safety device in case your BCD fails or your dry suit floods or as a safety stop line. (in case you miss the anchor line) What type of line would you use and would your procedures change? Would you weight the line and come up as you would on an anchor line, so you would not drift?

Just starting to formulate some questions. I want to get some different opinions and viewpoints.

Thanks

Joe

Reg Braithwaite · Dec 9, 2008

Welcome aboard! I'm also fairly green and like to ask questions.

What I will say first about deploying an SMB is that it's a physical skill. As such, we can describe it for you, but there really is nothing like having physical instruction in the water. In my own case, it was part of my PADI OW (cue the cat calls) drift dive.

Second, I will say that there is a DVD called Intro to Tech that shows the procedure for deploying an SMB from a finger spool. Beg, borrow, or bittorrent a copy and watch it.

I'm sure others will walk you through the steps here. The third thing I will say is this: an SMB is an entanglement hazard, big time. It can get caught by a boat and drag you to your death if you get wrapped up in the line. Learning how to deploy an SMB properly is important.

Finally, I will say that you should practice. In my own case, I once deployed one and I was so wrapped up in winding the line onto the spool as I ascended that I didn't dump the air from my wing and dry suit. The next thing I knew, I was in a runaway ascent and had to dump everything, pronto, while not letting go of the reel.

If I was more comfortable deploying the SMB, I would have had more of my brain free to think about venting gas and communicating with my team.

Doc Intrepid · Dec 10, 2008

Joe,

A lift bag and a surface marker bouy are often not the same thing.

They CAN be, but like many other compromises, an object designed to do both things often winds up doing neither optimally.

A surface marker bouy needs to be visible from the deck of a charter boat, its often a column that stands up 4-6' off the surface of the water. There are at least two types, open and closed circuit. A closed circuit SMB can be inflated (on the surface, not underwater) until it is rigid. Because its fully inflated, it offers a couple advantages: (1) it can be removed from the water and waved - as at aircraft or boats; (2) it can function as surface support for an exhausted diver.

An open circuit SMB has no capability to be rigidly inflated because the bottom of it is open (or secured only with a nylon flap). It works great so long as the open end is submerged. If you lift it out of the water, however, it will not maintain its rigidity. If you put a lot of weight on it, as in a wounded or exhausted diver, you must find some way of securing the open end or the gas will escape.

Examples:
Halcyon: Lift Device Overview

Halcyon: Diver's Alert Marker

Notice how the overfill relief valve is located near the bottom of the tubular structure. Tough to release gas unless nearly the entire tube is filled - the gas tends to seek the highest point.

In contrast, a lift bag is used to recover objects - an outboard motor, for example. The overpressure relief valve will be found closer to the top of the bag, where the gas collects first, so that it can be released when the bag is nowhere near full.

Lifting objects can be problematic, especially as the objects get larger. Divers have been killed trying to lift cars. Accounts can be found on this board of such fatalities if you do a search.

Larger objects are often lifted using teams of divers and multiple lift bags. The object may be neutrally bouyant in the water, but it still possesses potentially lethal mass. It needs to be controlled, all the way to the top. One technique, as an example, uses a line with eyebolts installed every 20-30 feet. The lift bag only occurs repetitively from 20-30 feet to the surface, then another bag is installed, and the object again is lifted another 20-30 feet. This keeps the divers above the object being lifted.

Here are some examples: (note where the overpressure relief valves are installed...)
Halcyon: Closed Circuit Lift Bags

Air Bags Open Bottom Lift Bags

Air Lift Bags Boulder Bags

Air Bags Lift Bags Air Lift Bags Safety Sausage Tubes Safety Sausage

What you're likely looking for is a personal Surface Marker Bouy (SMB) and a spool, to start off with.

But thats just an assumption.

FWIW, there is a lot of ground to cover before you start shooting bags. Quite a few fundamental skills to nail down first. Go for it if you want to, but you may want to wait awhile before you buy - unless you want to end up like the rest of us: we all have closets full of dive gear that we bought thinking it would be great, only to find out later that we needed/wanted something else.

We never use it now. But it sounded great at the time!

(Perhaps you should discuss this with your instructor?) Just a thought!

Enjoy your class dives,

Doc

jpitz31 · Dec 10, 2008

Thanks Reg for the introduction and feedback.

Doc, Thanks for all of the links and info. Yes, I will grab my instructor and discuss these topics. In out course materials there is brief mention of using a SMB for drift diving but not much more.

I will wait on the purchase until I discuss with my instructor. But I will more than likely purchase a closed circuit SMB for surface use.

We are heading to the Keys in January and I want to have a surface signal device as I hear the current can be swift at times.

Thanks

Joe

nereas · Dec 10, 2008

Doc Intrepid:
Joe,

A lift bag and a surface marker bouy are often not the same thing.

They CAN be, but like many other compromises, an object designed to do both things often winds up doing neither optimally.

A surface marker bouy needs to be visible from the deck of a charter boat, its often a column that stands up 4-6' off the surface of the water. There are at least two types, open and closed circuit. A closed circuit SMB can be inflated (on the surface, not underwater) until it is rigid. Because its fully inflated, it offers a couple advantages: (1) it can be removed from the water and waved - as at aircraft or boats; (2) it can function as surface support for an exhausted diver.

An open circuit SMB has no capability to be rigidly inflated because the bottom of it is open (or secured only with a nylon flap). It works great so long as the open end is submerged. If you lift it out of the water, however, it will not maintain its rigidity. If you put a lot of weight on it, as in a wounded or exhausted diver, you must find some way of securing the open end or the gas will escape.

Examples:
Halcyon: Lift Device Overview

Halcyon: Diver's Alert Marker

Notice how the overfill relief valve is located near the bottom of the tubular structure. Tough to release gas unless nearly the entire tube is filled - the gas tends to seek the highest point.

In contrast, a lift bag is used to recover objects - an outboard motor, for example. The overpressure relief valve will be found closer to the top of the bag, where the gas collects first, so that it can be released when the bag is nowhere near full.

Lifting objects can be problematic, especially as the objects get larger. Divers have been killed trying to lift cars. Accounts can be found on this board of such fatalities if you do a search.

Larger objects are often lifted using teams of divers and multiple lift bags. The object may be neutrally bouyant in the water, but it still possesses potentially lethal mass. It needs to be controlled, all the way to the top. One technique, as an example, uses a line with eyebolts installed every 20-30 feet. The lift bag only occurs repetitively from 20-30 feet to the surface, then another bag is installed, and the object again is lifted another 20-30 feet. This keeps the divers above the object being lifted.

Here are some examples: (note where the overpressure relief valves are installed...)
Halcyon: Closed Circuit Lift Bags

Air Bags Open Bottom Lift Bags

Air Lift Bags Boulder Bags

Air Bags Lift Bags Air Lift Bags Safety Sausage Tubes Safety Sausage

What you're likely looking for is a personal Surface Marker Bouy (SMB) and a spool, to start off with.

But thats just an assumption.

FWIW, there is a lot of ground to cover before you start shooting bags. Quite a few fundamental skills to nail down first. Go for it if you want to, but you may want to wait awhile before you buy - unless you want to end up like the rest of us: we all have closets full of dive gear that we bought thinking it would be great, only to find out later that we needed/wanted something else.

We never use it now. But it sounded great at the time!

(Perhaps you should discuss this with your instructor?) Just a thought!

Enjoy your class dives,

Doc

Exactly what I was going to say, as well!

So, to recap:

SPOOL not reel.

SMB not bag.

And forget about the urban legend of using a bag to substitute for a ruptured B/C. If you were ever in such a situation and you did not have a real backup such as a double bladder wing or else a drysuit on, then you would most likely careen down into the depths of Davy Jones' Locker, before you could ever deploy a bag, and that would be the end of you. They don't tell you that in the urban legend version.

Reg Braithwaite · Dec 10, 2008

nereas:
And forget about the urban legend of using a bag to substitute for a ruptured B/C. If you were ever in such a situation and you did not have a real backup such as a double bladder wing or else a drysuit on, then you would most likely careen down to the depths of Davy Jones' Locker, and that would be the end of you. They don't tell you that in the urban legend version.

While neither agreeing nor disagreeing with my esteemed colleague, I would suggest you ignore this paragraph. It is unlikely to matter until such time that you are fooling around with steel tanks and doubles.

You will note that no major agency trains the use of redundant lift in its basic OW course. Instead, they advocate diving with a rig such that by ditching your weight belt you can swim to the surface.

That really is all you need to know for a great deal of time. Resist the temptation to start arguing about the correct way to vent gas from a lift bag as you use it to ascend from the depths with twin steel 130s and a wet suit. Shun anyone who wants to harangue you about what is wrong with a "Bungied Double Wing of Death."

nereas · Dec 10, 2008

Reg Braithwaite:
While neither agreeing nor disagreeing with my esteemed colleague, I would suggest you ignore this paragraph. It is unlikely to matter until such time that you are fooling around with steel tanks and doubles.

You will note that no major agency trains the use of redundant lift in its basic OW course. Instead, they advocate diving with a rig such that by ditching your weight belt you can swim to the surface.

That really is all you need to know for a great deal of time. Resist the temptation to start arguing about the correct way to vent gas from a lift bag as you use it to ascend from the depths with twin steel 130s and a wet suit. Shun anyone who wants to harangue you about what is wrong with a "Bungied Double Wing of Death."

However he brought the urban legend up, not I, therefore I want to put it to rest.

Therefore it should not be ignored.

Where did you get that??? :no:

texdiveguy · Dec 10, 2008

There are 'several methods' that typically get introduced to divers either in Adv Wreck or Trimix level courses for deploying a lift bag and attaching it to a fixed object such as structure on a wreck and then using such as your ascent line without being blown off the site into a drift deco situation.

Blackwood · Dec 10, 2008

nereas:
And forget about the urban legend of using a bag to substitute for a ruptured B/C. If you were ever in such a situation and you did not have a real backup such as a double bladder wing or else a drysuit on, then you would most likely careen down into the depths of Davy Jones' Locker, before you could ever deploy a bag, and that would be the end of you. They don't tell you that in the urban legend version.

Maybe if you are in blue water (no bottom, deck, etc. near by) you can't deploy a bag fast enough. But most people don't dive in blue water without some sort of upline already in place.

I can't think of many things that are going to destroy your primary lift besides the obvious: tearing the wing. If you tear it, you're nearby whatever tore it, and you can use that something to support you whilst inflating the bag.

texdiveguy · Dec 10, 2008

Blackwood:
I can't think of many things that are going to destroy your primary lift besides the obvious: tearing the wing. If you tear it, you're nearby whatever tore it, and you can use that something to support you whilst inflating the bag.

Actually, most wing liners are breached while storing and moving gear around, pretty common cause. That's why it's always so important to store gear to avoid damage. This is much more common than in water damage of liners.

SMB, lift

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