Posted by: towmasters | September 15, 2009

Synthetic Snap-Back: It Really Does Happen

Humans often display are strong tendency to not believe that something bad can or will happen unless presented with what they consider to be undeniable proof of it. That undeniable proof, of course, often must (and does) take the form of the actual occurrence of that event which was specifically warned about before it is finally taken seriously.

So here is a timely reminder for everyone that may have forgotten, or never got the safety memo, that mooring/working lines do, in fact, part and kill or maim those on the receiving end of that release of stored energy.  Standing in close proximity to them, especially if they may get shock loaded, is just plain stupid. New Zealand, a small country, has had a half dozen such incidents  in the last ten years, so check out Maritime New Zealand’s September 2009 Lookout! newsletter. On pages 10 & 11 you’ll find an article about a line handler who was killed when a ship’s spring line parted and struck him, the dreaded “synthetic snap-back.” This kind of accident happens at a slow but steady pace, year after year. I frequently find myself on the radio reminding one of my deckhands and/or a tankerman to either stand clear of a line I’m going to work on, am working on, or to have them verbally warn a terminal’s dockman to stand clear until I’m ready to take in said line. Do they feel that they become immune to the danger after a time? Do they just space out and forget about it? Are they high on benzene and without a care in the world? Who knows…..anyway, read a little more and learn.

As for inspections of working lines, many still subscribe to the “if it ain’t broke, don’t fix it” principle. Under that principle, sufficient evidence that a line is abraded or weakened to the point of having to cut it back or replace it is only attained once the line finally parts. D’oh!!! Usually, no one is hurt. Usually…..

In the same newsletter there are two other little gems. First, on page 6, we find a hard lesson in the fact that sometimes your satellite gps receiver isn’t completely trustworthy and relying on it as your primary or sole means of navigation is just asking for trouble. How many people navigate this way? Lots, including many “professionals” who are distracted, lazy or never mastered the other navigation skills in the first place. In this case it was a rescue boat crew that erred badly while trying to help a yacht in trouble in rough seas. Serious injuries occurred when they struck a rock head on at 16 knots.

Finally, on page 13, we come to the bizarre but true and very sad story of a small launch skipper whose clothing got caught up by a spinning drive shaft universal joint, resulting in his being pulled in and strangled to death by his own twisted up shirt.  How did he get snagged? Because he was reaching around and under the spinning shaft. Why was he reaching around a spinning drive shaft? Because he was searching for the source of flooding after he lost situational awareness and struck some rocks at night. Then he made the final and fatal mistake of forgetting to take the engine out of gear before groping around in the bilge. Besides being twisted up in his own shirt, he was also being held underwater as the boat flooded, so if he hadn’t strangled he would have drowned. How’s that for a freakish and catastrophic chain of events?

For those who won’t accept the written word (and simple logic), no matter how persuasive, here’s a video that might get your attention. Watch as the Canadian Navy convincingly demonstrates the power and danger of  synthetic snap-back…..


  1. amazing view . . . accented by boiling water, of a towline parting.

  2. I learned respect for lines in tension OH many many years ago now (was in my teens) – a little 1/4″ (yes, you read the right, 1/4″ ) line under heavy hand tension snapped on the OTHER side of a turnbuckle I was installing. Lost 2 teeth in that incident, and got a bunch of stitches, and like I said, I was pulling that line by hand

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