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Failed Soft Shackle

Single-braid Dyneema is a godsend for anyone who wants to dabble in splicing lines for a sailboat. It’s very strong yet easy to work with, and not terribly expensive. This makes single-braid Dyneema ideal for DIY running rigging projects.

DIY Rigging

There are pros and cons to making your own running rigging. Pros are obvious, DIY can save quite a bit of cost. On the other hand, if you don’t know what you are doing, you can end up with unreliable rigging.

If you have done any serious sailing, you know how things fail on a sailboat at the worst time. To me, DIY rigging that is executed poorly is just another thing that will fail. The question will be when not if. So I was determined to take time and effort to learn to do things right.

Soft Shackles

Honestly, I took up DIY rigging for my J29 sailboat not just for the money saved. I also wanted to attain the skill. It always makes sense to DIY small things on a sailboat. Even if I were to resort to professional services to have mission-critical rigging done, I still want to be self-sufficient to build or repair if the need ever arises.

Another reason is that I really liked the idea of soft shackles. I became very intrigued once I learned about it, which led me to learn how to make a few variations. This got me even more interested in using them on my sailboat.

I made a number of soft shackles to practice, then slowly deployed them on my sailboat BlackJack. Starting with low load applications then progressively on higher load applications.

So far the results are excellent. I have been out in 15-20 knots a few times with sails flogging, and none of my soft shackles have failed catastrophically. I would sail in more wind, but this is all we get in San Diego.

Then One Failed, Sort Of

As part of the deck check when I go sailing, I check all the soft shackles, looking for signs of any chafe or deterioration.

And one day, I caught the diamond knot in one of the soft shackles starting to slip.

I took the soft shackle off of the boat and tried to get it to fail by applying various loads. Eventually, the tails came out and made the diamond knot smaller. The shackle still held, however.

This will increase the chance of shackle opening, but it is good to know that it will not result in an instant failure. Soft shackle fails softly. That’s good to know.

Failure Mode Analysis

The hardest part about making a soft shackle is creating a tight diamond knot. I clearly did not make the diamond knot tight enough on this shackle. And I know why. This particular shackle was one of the first ones I made. I was having a hard time making a tight knot using a smaller pair of pliers.

In fact, this soft shackle was the only one on the boat made using the small pliers. Once I realized I needed better leverage to tighten the knots, I used a big channel lock pliers. The remaining ones made using channel lock pliers show no sign of slipping.

I will stick with making soft shackles, but a lesson learned. I will always be using channel lock pliers on my soft shackles, thank you.

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