Lift bag technique.

[abitton]

When launching a bag in mid water, I will partially fill it with air by dumping from the wing inflator into the bag as you then remain neutral until you release the bag.

Simply brilliant. Now why didn't I think of that... So much easier to maintain control over buoyancy then when adding air through the reg exhaust...

I am NOT being sarcastic, BTW...

 

[ClayJar]

How many dives does this rocket scientist of a DM have? Second question is, how many of them are actual non-class related dives?

I have not a clue. He wasn't young looking, and his gear didn't have that dive shop sheen... I would assume that he's been diving at least several years, but honestly, I didn't see any reason to have a big conversation with him.

I'd never seen him before, and I was skeptical of his advice, especially at his having dismissed my question so easily without discussion. Obviously, with only 50-some dives since I was first certified, I'm hardly an expert, but I assimilate any information I can find, and I don't think highly of "Because." as an answer.

 

[DA Aquamaster]

I think Quarrior was referring to the usage of a lift bag as a surface marker, in which case it should be released to fly. When actually lifting something, one should stay with the bag.

I think that increases task loading and can cause other nasty problems.

My preference when I find an anchor is to send it all the way to the surface on either a finger spool or reel or carbineered to the dive flag line if I am the unlucky person dragging it.

Also, when doing a really large lift with, for example, a 500 lb bag you've got too much gas to readily control it during ascent so sending it up is your only option, as is also the case with any closed circuit bag or any smaller bag lacking a dump valve.

Many small to midsize lift bags have dump cords on the bottom side of the bag leading up to the dump valve on the top. These can be dangerous as they create the potential for you to get snagged in the cord, straps etc. If this occurs during your ascent and the dump sticks open in mid water (due to tension on the cord), you are going to get drug back down to the bottom with the bag and object. Guess how I learned that one.

Personally, I now reverse these dump valves so that the valve is operated by a very short cord from the top of the bag (and basically used only to drop the bag from the surface)

When you send the bag up you want to be sure your reel or spool is not going to snag. This means fully stripping the line and carefully rewinding it prior to any dive where you anticipate shooting the bag to ensure it will come off neatly and cleanly. If it does snag - let go of it and hope you find it later.

When send up an object, you also want to be aware that what goes up may come down. The best course of action is to keep your eye on it as long as visibility permits while at the same time swimming laterally away from the spot where you launched it as that is the most likely impact zone if the bag fails, rigging breaks, etc.

I have seen this pay off big time once when a bag ruptured on the way up, sending a 500 lb concrete anchor back down on the spot just vacated.

 

[Soggy]

I think 500 lb lifts are a bit beyond the scope of what someone without additional training/experience should be doing, and I will concede that I know absolutely nothing about what is involved in such an undertaking.

For small lifts that most people would be doing, staying with the bag is your best bet from a safety perspective, IMO.

 

[mfalco]

I have seen this pay off big time once when a bag ruptured on the way up, sending a 500 lb concrete anchor back down on the spot just vacated.

Exactly why you don't want the lift bag to be positively boyant. That's like lighting a stick of dynamite, and running away. What happens if you trip?

Neutrally boyant with you next to it. If anything happens, the falling object can't hit you. If the bag starts becomming positive, you let a little air aout the dump valve.(that's what it is there for)

 

[rongoodman]

On a somewhat related note... I've seen many cautions against using carabiners to attach things to a harness/BC because of the snag potential and I use snap links too. Is it safe to use carabiners to attach an object slung with rope or webbing for lifting? It seems like the larger gate opening would made life easier in this situation.

 

[TheRedHead]

He signaled me to dump air and get on the bottom of the pool, and then when my buddy and I surfaced, he chided me for floating and told me that I should *always* be heavy and kneeling on the bottom when using a lift bag.

Ask him what to do when the bottom is 150 feet down. I learned to shoot a bag in the water column in Cozumel. The DM has led a sheltered diving life.

 

[ClayJar]

Ask him what to do when the bottom is 150 feet down. I learned to shoot a bag in the water column in Cozumel. The DM has led a sheltered diving life.

With luck, I won't have the opportunity to question him again, however, if I were to prognosticate on his possible response, I would venture to say that he would be adamant that I must shoot the lift bag from a fully upright position, and that shooting it while horizontal is just crazy talk.

Incidentally, embedded in his comments was something about me having very bad form with my legs up the whole time. I managed to refrain from explaining the frog kick (versus his flutter-crawl), musing about what dives look like without the silt cloud, or opining that, if I'm lucky, I'll never have to swim behind him on a dive. :shakehead

 

[TheRedHead]

Clayjar, there is really nothing you can do with DMs like that except humor them. When you finish your class, you can call him a stroke. :lol:

 

[ClayJar]

Oh, don't worry. I'm diplomatic enough to know when to humor someone. As for calling him a stroke, nah, not my style. I'm far more dry a wit than that.

Best part of the reasoning was that if you're not kneeling, you'll be finning constantly and wasting all sorts of energy. I suppose that is indeed what would happen if you had poor buoyancy control, but considering I regularly goof off underwater whenever it's safe and acceptable, I don't have a problem with buoyancy.

My favorite game from last weekend was sitting at the cavern at Vortex Spring and watching divers with rudimentary skills. They'd fin/crawl/walk around, and I'd just flip my feet up and my head down, hover inverted, and watch the show. A couple of them actually understood the implication and adjusted their buoyancy a little. If you can hover while completely inverted a foot or less from the rocky bottom, you're probably going to be able to handle a little knot while horizontal, eh?

Oh, a little kudos to one of them... The guy was silting up the place as he went into the cave, at which point I was rather displeased with him and his buddies, but when they came out of the cave, he saw the litter collection I had been building on a large boulder (to take it all up at once), finned by it, and took it up for disposal. Anyone who is considerate enough to pick up litter on a dive (even well-packaged pre-collected litter) gets my respect. If you think about picking up litter, you're showing initiative which likely will also mean you'll become a better diver with time and experience.