Harken Derm

Shackle vs Rope Block Attachments…the facts revealed

Published on September 29th, 2015

by Dr. Harken
Shackles have been used by sailors for many years to attach blocks to boats. They are not only reliable and strong, but are also excellent indicators as to when a block might need replacing.

Deformation or distortion on the shackle is a good warning sign that the block is working at its maximum load capacity and could be due for replacement or service. Distorted shackles help ensure we change our blocks before breakages occur which are, let’s face it, usually right in the middle of a race when we don’t want them to fail!

So why deviate from the norm when a shackle works perfectly well?
With today’s advances in rope and materials technology, we are seeing an increased demand for lighter, stronger, go-fast equipment, and an evolving trend toward soft-rope attachments-from dinghy and weekend sailors, to elite British Sailing Team athletes and Olympic hopefuls, to Volvo Ocean Race and Maxi sailors.

Is Dyneema® rope strong enough?
‘Rope?’ you ask. ‘How can it be strong enough to hold the high loads on my blocks?’ Well, in fact, when compared on a weight basis, Dyneema is 15 times stronger than steel wire. That’s pretty strong! On top of that, it is lighter than a steel shackle and buoyant enough to float in water.

Chafe is another consideration. Rope is kinder both to your boat and to your hardware. In addition, soft-attach options allow better articulation than a shackle. This means the load being pulled through your block will be at an optimal angle, reducing the risk of breakage, and space taken up on deck.

Why isn’t everyone using soft-attachments?
For all their benefits, there is a lack of understanding of the advantages of rope attachments among sailors, as well as the fear of trying something new. In addition, wear and chafe on rope attachments is easier to spot and requires regular inspection more often than a shackle.

Another common reason why people have had problems with soft-attach solutions is that they have experienced block breakages. These breakages in the dinghy range are most often due to blocks being tied incorrectly.

Therefore, it is essential that the installation of your soft-attachment is correct for your specific fitting and not just simply “tied” on. Full report.

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