Boat snaps cable during loading - GIF

[Jon]

Boat snaps cable during loading. No gore, and I'm assuming nobody was on the dropped boat. Anyone know what's happening here? Incorrect cable length? Angle? Strength?

To make matters worse, the boat capsizes.




Previously:

Pulling a boat through locks GIF
Cubans flee Communism with American cars converted into boats
Boat that pulls itself ashore
Sealegs amphibious fishing boat
Trailer with built-in boat as roof
Flying inflatable boat
Van/boat combo - GIF and video
Airplane fuel tanks turned into Vietnamese boats

[awright]

Well, of course we don't know the weight of the boat, the strength of the cable, or if possibly the boat struck or dragged on something on the deck/pier, but the roughly 45 degree angle of the two cables would increase the tension in the cables by the square root of 2 (i.e., 1.414) times the tension that would exist in vertical cables, each carrying 1/2 the weight of the boat. The clearance between the block and the crane arm above is not shown, but the riggers would have been making better use of the cable load capacity by increasing the height of the block above the boat and minimizing the clearance between the block and the crane arm.

Also, I think there is a slight tilting of the boat forward just prior to the cable break and that would have shifted load from the rear cable onto the forward cable, making a marginal situation worse. (I'm using forward here to indicate toward the bow of the boat being lifted.)

Another thing comes to mind: Notice that a barrel or something tumbles forward just prior to the break. That may be a clue that "stuff" inside the boat or even bilge water also tumbled forward, shifting more load onto the forward cable.

[Jon]

Similar, but more dramatic, and probably more recoverable if they can right the crane.

[kutzbill]

Great eye! I was thinking that the wind caught the barrel, and that cause the shifting of the ballast or cargo inside the ship. Cables are so tricky, because it has been my experience the people that use them seem to think they last forever. I have seen a 20 ton crane with cables that have several bulges in them, and the owners didn't want to replace the cables! They were moving large electric motor armatures over some of their workers.
I actually had to prove the cable was weak by cutting it apart.
More than likely the riggers figured out everything and had good cables here, but the wind and/or shifting of weight caused this accident.
I have to admire the guy jumping over the snapping cable reflexes though.
Smiles!

[Frank S]

The thing I saw was the riggers had used only 2 slings doing the pick from the centers of the cable slings this is a definite hazard just waiting to happen as the strands in the rope are stressed far beyond their normal rating Any time a wire rope is subjected to this kind of use it must be de rated and should be de rated several times lower than straight line pull cap. There are rope lings designed for center point pull but theses have a stress relieving pad served right on the rope often a complete eye so if either side of the rope should break the other side will still hold it's share of the load. But good rigging would never have used only 2 slings they would have had 4 slings and these would have been much longer. the longest possible and still retain minimum distance between the old man and the head

[Jon]

Another nice one, featuring an Indiana Jones-style cab escape.

[LMMasterMariner]

When one is dealing with lifts like this one, slings must be thoroughly inspected and of correct SWL. And of course angle between slings is very important. 2 pages from my notebook (book of knowledge) attached.
Therefore spreader should be used to have slings as much vertical as possible, i.e. angle between slings zero or very close to zero as you can see from attachments.

Regards
LMMasterMariner

[Jon]

Crane fall video. Looks like the operator bails out around 1:20. 2:02 video: