Cheap Boat Tricks: Dyneema Soft Shackles

Although we have a little apartment in San Carlos, I still spend a lot of time down at the boat. I like to go down in the morning when it is still sort of cool and have my coffee in the cockpit and check in on the cruiser’s radio net. The cruiser’s net is short and sweet this time of year; there are only four or five boats and after that I get busy with a few projects. It is a pleasant routine that has allowed me to tackle those little chores that always seem to get pushed to mañana.

This week I started making new soft shackles for Galapagos. For the uninitiated, a soft shackle is a loop of very strong line, with an eye and a large knot that acts like a shackle.  In many places where you might need a strong stainless steel shackle, this soft, easy to make device can do the job better and with less cost.

Five new Soft Shackles made from 1/4 inch Dyneema winch cable. All five were made for less than twenty dollars.

If your eyes started to glaze over after that last paragraph, that’s okay.  Not everyone really cares about button knots or Ultra High Molecular Weight Polyethylene rope.  Feel free to scroll to the bottom of this post for a picture of an interesting insect.

For the rest of you really cool people, I will share some of the links and tricks that have helped me learn to make soft shackles and improve my technique as well as a source for Dyneema that has been much less expensive than a chandlery.

To get started in making Soft Shackles I have found that by Allen Edwards is a great resource.  He has a number of pages now devoted to making soft shackles of various types and for special applications. To get started and to keep things simple, I like the Better Soft Shackle. The instructions are easy to follow and importantly, Allen has a small calculator built into the page to allow you to determine the measurements needed for a specific diameter of shackle. Be sure to check out the other topics available on  Lots of good stuff there. And of course there are tons of YouTube videos to help you along the way.

Fifty feet of Dyneema 1/4 inch line for $19

I should make it clear that I am using the trademark name Dyneema  for the material that is more generically, and far less melodically known as Ultra High Molecular Weight Polyethylene (UHMWE) Since Ultra High Blah Blah Blah doesn’t really roll off the tongue, let’s just continue calling this stuff Dyneema. Like Xerox means copy and Kleenex means, well, Kleenex. Spectra is another trademark product name for this type of line.

Most of the line I use on Galapagos for soft shackles is 3/16 or 1/4 inch.  1/4 inch Dyneema has a breaking strength of over 7000 pounds which is more than adequate for almost any application on our boat.  You can go to your favorite marine chandlery and buy Dyneema line made by Samson in a variety of colors and with additional coatings to protect the line.

Samson line is great but if you would like to save some money for the same material, check out winch cable replacement line on Amazon.  Apparently, off road vehicles, snow plows and other road machines that carry electric winches are now switching from steel cable to Dyneema line.  Most of the items I see are 50 foot lengths with an eye and stainless thimble already on one end.  Some of the product will have a hook spliced on as well which isn’t particularly useful but who knows.  The important thing is that for less than twenty bucks you can get 50 feet of Dyneema that works as well as the marine store brand. BTW, West Marine is selling 1/4 inch Samson Dyneema for $1.62 a foot.

Here is one link to the kind of cable we are talking about. Synthetic-Winch-Rope . You can find similar products on E-Bay as well.

Update on quality of Dyneema 9-14:

Astute reader Jamie Gifford of Sailing Totem pointed out that there is a difference in quality between the Samson Dyneema and the winch cable being sold on Amazon.  The Samson product is a higher quality product with a higher breaking strength and it is backed by the reputation of an American company that makes rope for numerous industrial applications.

The winch cable on Amazon by contrast is made in China and is of a lower quality.  In fact it would be difficult to know exactly what kind of Dyneema is being sold but it is safe to assume that the breaking strength of these winch cables is going to be lower than the Samson product of a similar diameter. A quick search for load testing of the Chinese line showed that it broke at about 76 percent of a recognized brand of the same diameter.

That said, this material is still incredibly strong and is a great value if your application will not approach the maximum break loads of the material.  If you have a critical, high load application, use the best material you can buy for that application.

These are some of the old soft shackles we keep at the helm. We have a similar collection at the mast pulpits.

I could bore you with photos of me dramatically making brummel splices but I’ll spare you.  I will, however share some photos of the knot required.  The knot is an important aspect of the shackle and must be tied correctly and be cinched down as tightly as possible to prevent it from inverting under load.

This Carrick bend forms the basis of the button knot. Pretty, no?

To add additional bulk to the knot, the two ends are brought around and up through the center.

The site has instruction for tying this knot here.  Even though I’ve made several of these knots, I find myself referring to L-36 instructions to refresh my memory often.  I find it a tricky knot to tie properly.

Tightening the knot requires considerable force. I use a pair of vice grips and leverage to pull the knot tight. When I’m done the knot should feel as hard as a block of wood.

If you’ve been curious about soft shackles and how to make them, I hope this post will encourage you to spend a few bucks and try your hand.  Once you’ve made a few for yourself and tried them on your boat I think you will find them dead useful.

Name That Bug!

Alright. Now that we’ve gotten the boring stuff out of the way, perhaps you can help us identify this insect. I’ll admit this isn’t the cutest bug we’ve seen down here but I’m sure his mother thought him, or her, quite beautiful. Any entomologists out there that can ID this critter? Leave a comment.

We found this fellow in the pool and rescued him from certain death. That’s his grateful look.