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Shackle vs. Soft-Attach

In this article:

  • Pros and cons of shackle vs. soft-attachment options
  • Traditional forms of block attachment
  • The advantages of new Dyneema® rope technology
  • Common pit falls with soft-attach installation and how to do it right

Sailors have used shackles to attach blocks to boats for generations. Shackles are reliable and strong, and excellent indicators of when a block might need replacing. Deformation or distortion of 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 often (let's face it) happens right in the middle of a race when we least 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 Olympic hopefuls, as well as crewed offshore racers and solo sailors.

Is Dyneema® line strong enough?

You might ask how line can be strong enough to hold the high loads your blocks can handle. On a weight-to-weight comparison, Dyneema® is 15 times stronger than steel wire. That's pretty strong! On top of that, it is 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 provide better load balance than a shackle. This means the load being pulled through your block will be presented at an optimal angle, reducing the risk of breakage, and minimizing space taken up on deck.

Why isn't everyone using soft attachments?

For all their benefits, soft attachments aren't perfect for every situation. For instance, rope attachments are more susceptible to wear and chafe, and require inspection more often than a shackle.

Another common reason people experience problems with soft-attach solutions is block breakage. These breakages in the dinghy range are most always due to blocks being tied incorrectly.

Therefore, it is essential that the installation of soft-attachments is correct for the specific fitting and application -- not just simply "tied" on. Find information on installation instructions on our website:
Carbo® T2 blocks (tie/splice)
Carbo® T2 loop blocks
Black Magic® loop blocks
Fly™ soft-attach blocks

In what circumstances should I use a shackle or a soft-attachment?

The main advice here is that soft attachments require smooth radius attachment points. Sharp or rugged edges, like toe rails, can cause wear/weak points to form in the rope. If edges are rough, using a shackle would be more appropriate. If the surface has a smooth radius, then a lighter soft-attachment would be indicated.

Select soft-attachment whenever greater articulation is required and weight is a consideration.

How to tie a soft-attach block correctly.

Block failure in the soft-attach range is mainly due to incorrectly installed soft-attachments. To combat this, here are examples of the correct and wrong ways to tie on soft-attach blocks.

See images below.




Soft-attachment explanation: Andy Ash-Vie, managing director of Harken UK, explains the benefits and uses for soft-attach blocks.

When it comes to choosing between shackles and soft-attach, the choice is really as individual as each boat and sailor. It's clear there is a shift toward using soft-attach options because of the performance benefits and weight reduction discussed above. The key is to ensure that the soft-attach blocks are installed correctly!

How do you install soft-attach blocks?

Harken makes it easy with simple-to-follow installation guides, downloadable from our website.

Click here for T2 blocks
Click here for Fly blocks
Click here for Black Magic blocks

So why are soft-attach blocks so special?

  • Lighter and stronger alternatives to shackles
  • Simple to follow installation instructions
  • On-hand technical support
  • Easier to identify chafe
  • Greater articulation for optimal load displacement
  • Kinder to boats and hardware

Soft attachments are ideal for:

  • Traveler controls
  • Mainsheets and vangs
  • Cascades
  • Bridles
  • Other systems requiring a lightweight solution

Things to watch out for:

  • Installation: Read the instructions and tie on blocks properly. Questions? Call the Harken Tech Team.
  • Chafe: Check soft-attachments regularly for chafe and wear.
  • Maintenance: Wash regularly with fresh water.


Still have questions?
Watched the video, read the instructions, but still have questions? Feel free to contact the Tech Team at any time via the link below:


Dyneema is a registered trademark of DSM IP Assets.

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