Question Lift Bags

[icechip]

The other day I used a couple of lift bags to move a boat mooring out to deeper water at a lake in Maine. Did not have to bring the mooring granite pads (two of them) to the surface, just needed to get them buoyant enough to move about 15 feet farther out from the dock. All in about 20 feet of water. Interesting (and eventually successful) effort, but it was trial and error as we went along. It also got me thinking about lift-bag use in general and lifting more substantial things than a couple of 130# round granite pills. Anybody have some good "does and don'ts" or some stories from people with lift-bag experience?

 

[slimshady]

Hmmmm....do's and don'ts? Background: I have been using lift bags, all types, from recreational 50# to commercial 4400# to lift and lower boats, trucks, cars, airplanes, buses, blocks, weighted airline, etc. Shallow water small lift bags can be manageable up to 100# of lift provided you as the diver are part of the weight. Managing the item with just the bag is frustrating as the item ascends or descends quickly and volume in the bag changes. With larger bags I typically use a parachute rig as a seond bag, or set of bags, secured above the primary item to prevent the porpoising of the bag as it rockets to the surface from deeper water, or crashing to the bottom, once the volume increases or decreases depending on whether you are rasing or lowering the item. Pillow bags are great for shallow water and stability, but positioning is more important so the bag can get full lift and not be folded or compressed between something like a fender or door. Open bottom bags are very versatile and easy to use. Number one piece of advice, don't try and finese the larger bags. When lifting just put air in until it goes. When descending put air in until it drops. Hope this helps. My experience is from a Search and Recovery Dive Team.