Breaking Mooring Lines

by Jerry Powlas

We are doing a little household remodeling and needed to remove some bushes in the front of our house. The major task was to tear out three large bushes, two of which (when pulled out) Karen and I could lift together and one of which we could not lift. We were fortunate that the ground was very soggy following torrential rains.

The contractor had said to put a chain around the bushes, tie it to our truck, and just pull the bushes out. As we didn’t have a chain I was willing to use in that way, we used old mooring lines.

The lines were mostly 5/8″ diameter, double-braid nylon. All of these lines had spent some years in service and been retired mostly because they looked faded. Most had become fairly stiff and hard, as nylon is want to do when it ages. None of these lines had obvious worn spots.

It was an interesting experience. The lines parted about five times as I recall. Snap-back was a problem, even when the bush yielded as well as when the lines broke. I finally resorted to using double lines. This got me a breaking strength high enough to rip out the bushes without having the lines part first.

Knots were a problem. The taught line hitch would not hold under these loads. I think that’s because, as the load got higher, the line diameter got smaller and the turns simply slid along the line. The double sheet bend also failed. The line simply pulled through and the knot untied. Perhaps with more supple line the double sheet bend would have been OK. I settled on bowlines for everything. Once they had experienced stresses this large, the single bowlines were very hard to untie. Once I was using double lines for all the loads, I tied the bowlines with double lines, meaning that a pair of lines followed the same path as a single line normally would follow. This produced knots that held the load and could be untied.

Those single bowlines and some other knots I tried could not be untied, even with a fid. One knot appeared to have welded itself together, meaning that the plastic in the lines (nylon I think) melted and fused with other parts of the knot. More than one knot may have welded itself under load. I did not cut into all of the knots to see why I could not untie them.

The most interesting and unexpected part of the morning’s observations was that NONE OF THE LINES PARTED AT OR NEAR A KNOT. All the breakage occurred in the spans away from the knots. This is contrary to the notion that a knot weakens a line a great deal. The only failures that occurred near a knot were when the knots simply untied themselves the way knots in fine nylon twine do.

Our monster truck (named Scarlet) was able to break these lines pulling on the torque converter just above idle. I only resorted to 4wd and low range when I needed to climb a curb across the street at the same time I was pulling a bush.

We started using an anti-snapback snubber after the first bush streaked across the yard and almost made it to the truck. This safety precaution worked well.

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4 Responses

  1. Jerry,

    Regarding pulling shrubs with synthetic rope. Being a sailor and a professional tree guy, I’ve got a trick for untying a bowline that’s going to be under a terrific load. I have to preface this with the info that I use half-inch dia. dacron tree climbing rope that doesn’t stretch like nylon. When you tie the bowline, insert two dry 1/2 in. dia. sticks into the middle of the knot. After the pull, break the sticks. That always gives me enough slack to start working the knot loose. If the knot has the tendency slide apart (as you stated as a characteristic of nylon), start with a long enough tail to finish the bowline with two or three half-hitches around the standing part of the line. You may need to use the same stick trick on the half hitch closest to the bowline. One stick should be enough for the half hitch. Chain is better, and safer, however.

    Bob
    Richardson, TX

    • Bob,

      I’d like to include this discussion in an upcoming Mail Buoy column. That was good input and everyone will appreciate your “stick trick.”

      Karen Larson

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