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post #1 of 11 Old 03-22-2014 Thread Starter
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New Soft Shackle Design

There is a fascinating and long thread on Sailing Anarchy about load testing knots, harnesses, splices, and shackle designs. Already a new loop knot that holds in dyneema (Amsteel) has been discovered. Earlier this week a new shackle design was found and tested to be much stronger than existing soft shackles.

As a bonus it is also much faster to make! No more diamond knot.

The shackle is shown here (search for "Improved Soft Shackle")
Load testing

The full thread is here, the new soft shackle design is tested on page 10:
Rope/knot/splice load testing - Gear Anarchy - Sailing Anarchy Forums

Thanks to Evans for designing this version, testing it, and sharing the results. This is a great improvement over prior designs. I had nothing to do with it, just wanted to share it with SN.
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post #2 of 11 Old 03-22-2014
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Re: New Soft Shackle Design

Thanks for posting that. It looks like a good solution to the diamond knot failure point. One thing I do to strengthen the diamond knot is to soak it in some plastic tool handle coating dip. The stuff seems to really soak in and bind the diamond knot and make it like a rock. I have used them a lot recently and have never had one fail. The best use so far I've found for soft shackles is for attaching the snubber line to the chain. It makes a quick, sure connection. Amsteel is really amazingly abrasion resistant, rugged stuff.

One other thing to mention about the new method is that the two additional eyes need to be sewn as any 12 strand splice. With the short tuck, they would be very likely to slip without a few sewn loops through them.

Alberg 35: With a philosophical flourish Cato throws himself upon his sword; I quietly take to the ship.
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post #3 of 11 Old 03-22-2014 Thread Starter
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Re: New Soft Shackle Design

The eyes actually need to have a decent length tapered splice. It is important that the doubled up length go all the way through the overhand knot and end up part of the way down the legs.

There is no reason to sew them. You sew normal dyneema eyesplices to prevent them from pulling out under light load. On this the overhand knot (which sets very hard) does that job for you.

I use soft shackles all over the place on my boat. An anchor related one is holding the anchor up (by it's hoop on a Manson Supreme) to stay in the anchor roller. My favorite use for them is to hold the jibsheets to the clew of the jib, it's a lot more compact than a bowline and allows for quicker sail changes than a cow hitch.
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post #4 of 11 Old 03-23-2014
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Re: New Soft Shackle Design

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Originally Posted by Alex W View Post
The eyes actually need to have a decent length tapered splice. It is important that the doubled up length go all the way through the overhand knot and end up part of the way down the legs.

There is no reason to sew them. You sew normal dyneema eyesplices to prevent them from pulling out under light load. On this the overhand knot (which sets very hard) does that job for you.

I use soft shackles all over the place on my boat. An anchor related one is holding the anchor up (by it's hoop on a Manson Supreme) to stay in the anchor roller. My favorite use for them is to hold the jibsheets to the clew of the jib, it's a lot more compact than a bowline and allows for quicker sail changes than a cow hitch.
I know what you're saying about the overhand knot but Amsteel/Dyneema is so slippery, it can't hurt to have a few stitches through the splice. I'd be tempted to run a few stitches through the overhand knots to keep them from slipping.

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post #5 of 11 Old 04-02-2014
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Re: New Soft Shackle Design

Hey Alex, I was going through the SA thread again because I was thinking of ordering some Amsteel/Dyneema, and I see that you, Evans, and some others are playing with the design. Is there a stable version that would work in something like 1/4"?

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post #6 of 11 Old 04-02-2014
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Re: New Soft Shackle Design

Please keep in mind that Allen and Evans are trying to improve the holding power to get it up to the theoretical 4x the strength of the line it's made out of. The diamond knot works fine for loads that are less than the line it's made from. The subject of soft shackles on that thread doesn't really apply to 99% of the people out there. If you want a very lightweight and extremely strong connection, than building a strop with a dog bone is a better solution. And no knot to worry about.

If you make a soft shackle using the diamond knot, you can achieve the following breaking strength loads (these are very rough)
7/64 = 1200
1/8 = 2800
3/16 = 6000
1/4 = 9700

How many boats out there need a shackle that is rated at over 38,000 lbs? (4x1/4 dyneema).

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post #7 of 11 Old 04-02-2014 Thread Starter
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Re: New Soft Shackle Design

I like the new designs because they are faster and easier to make. I've made 20ish soft shackles using diamond knots and I still need to look the knot up to remember how to make it. The new EStar shackles I can make in about half of the time and they are easier to memorize. Diamond knot shackles can be made smaller which is good.

I make most of my shackles out of 1/8" or 7/64", the only reason on my 29' boat to go with 1/4" is make it a little easier. 1/4" works better with commercial fids and it is easier to see what is going on.

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post #8 of 11 Old 04-02-2014
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Re: New Soft Shackle Design

Same experience here. 1/4 much easier to work than the smaller sizes. Alex, can you point us at the specific post in that thread for construction instruction?
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Re: New Soft Shackle Design

It's in the link that I provided in my first email to this thread:
Load testing

Search for "improved soft shackle"

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Re: New Soft Shackle Design

Here's a direct link to Evans' PDF:
http://www.bethandevans.com/pdf/improvedsoftshackle.pdf

The part that I don't get is when he mentions loading up the knot using a winch. In that scenario, how are you putting the pressure on the knot?

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Last edited by jimgo; 04-02-2014 at 10:48 PM.
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