Lift Bag Usage

[pants!]

Wow WM... that's a heck of a process for lifting a 40lb hunk of brass and glass..

 

[redacted]

It beats the heck out of the other method, which is to attach a liftbag, add air until the object breaks free of the bottom, then goes hurtling towards the surface, only to come unhooked, fall back down and kill you.

Terry

I'm afraid I have been a bit cruder than that. When depth & weight are not too great, I simply shoot a bag to the surface and tie the line to the object, freed up so it is ready to lift. Finish an enjoyable dive, return to boat, and haul up the treasure. If the object (usually an anchor) is too heavy and the anchor rope is too short, it may take a 2nd dive.

 

[Web Monkey]

Uh, doing it (a free lift at neutral buoyancy) right and safely takes a little practice and technique, but it ain't exactly rocket science either...
Rick

(photo credit - Tom Smedley)

That depends on how deeply the object is embeddded in the botttom, and the bottom type.

If it's stuck in the mud or is buried to any significant depth, it takes a lot more lift to get it free from the bottom than is required to make it neutral.


Terry

 

[Rick Murchison]

That depends on how deeply the object is embeddded in the botttom, and the bottom type.

If it's stuck in the mud or is buried to any significant depth, it takes a lot more lift to get it free from the bottom than is required to make it neutral.
Terry

You're going to apply more lift than it weighs to get it free? Hmmm.... interesting. I suppose if you can't free it any other way then the limited (and complicated) 10' per lift makes sense. I may use some lift to assist in freeing an object, but (so far) never more than it weighs - less lifting and more digging.
In many of the places we recover stuff (the Gulf of Mexico) current is often a major factor, and running a line all the way to the surface would introduce a horizontal dynamic into the problem we may consider more risky than a little overestimation on the lift required to assist in freeing an object. I'll keep your method in mind, though, for that time we may need it
Rick

 

[pants!]

You're going to apply more lift than it weighs to get it free?

Been there done that, but isntead of a series of 10' loops, all it takes is one big tug to get the thing free (with a tool is preferable, but use a big bag if not), then you dump all the air from the bag, let it settlg on the bottom, and start a normal lift.

Of course, I haven't done this with any very large objects, but a 40lb porthole should not be much of an adversary...

 

[Rick Murchison]

one big tug to get the thing free (with a tool is preferable, but use a big bag if not), then you dump all the air from the bag, let it settlg on the bottom, and start a normal lift.

FWIW, I do not recommend this method.
Rick

 

[pants!]

FWIW, I do not recommend this method.
Rick

Care to elaborate?

 

[Rick Murchison]

Care to elaborate?

Sure.
(1) The method requires that the dump valve works well and (2) requires that the operator of the dump valve is "johnny-on-the-spot" and doesn't lose the bag and (3) having a greatly positively buoyant bag/object while trying to free an object is an invitation to entanglement and unpleasant surprises.
I prefer "seeking neutral" from the very beginning of the process - keeps things slow and controlled with no quick large actions or corrections required. Slow and controlled means more time to think and more time to act.
My little pea brain prefers that.
Rick

 

[The Kraken]

I absolutely refuse to disclose how I know this or who the divers are, but I know two guys who used a government surplus duffel bag and a large garbage bag to effect a lift once upon a time.

It was interesting, to say the least.

The K

 

[Web Monkey]

I absolutely refuse to disclose how I know this or who the divers are, but I know two guys who used a government surplus duffel bag and a large garbage bag to effect a lift once upon a time.

It was interesting, to say the least.

The K

That sounds like it should have worked just fine, until the bag breached the surface, vented the air out and sent the object hurtling back to the bottom.

Terry