DIY soft shackle

Discussion in 'Winching and Recovery' started by cartercd, Jan 31, 2017.

  1. cartercd

    cartercd SILVER Star

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    I thought I'd make some soft shackles as a lightweight (and less deadly) alternative to my 3/4" screw pin shackles. There are advantages and disadvantages to soft shackles that I won't address here, but they are another tool in the box. Here we go:

    1. Read the articles on L-36.com (a sailing website) at Soft Shackles. This has great info on various soft shackle designs and strengths. One of the articles has a calculator where you enter your rope size and desired shackle diameter and it will tell you how much rope you need. The calculator is based on the "classic" version, which I found overestimated my rope length for my version, but it gets you in the ballpark.

    2. Buy some rope. I don't skimp here - 7/16" Sampson Rope AmSteel-Blue Dyneema AS-78 with 24,000 pound average strength. I bought 14 feet from West Marine on sale at $2.90/foot, used for 2 shackles.

    3. I followed the instructions on L-36 for "High Strength Soft Shackle" using the button knot. The instructions use two different colored lines to make things easier to follow (this is not an easy knot). I put a piece of masking tape along one end to help me out, and then peeled it off before tightening the knot.

    ready for knot.jpg

    4. I struggled with this knot over and over again, and eventually figured out I was tying it correctly, but tightening it incorrectly. When you tighten the knot you need to keep all 4 strands of line pointing in the same direction. On my first attempts I ended up with lines pointing in different directions. Once I had it right, I set the knot with my Hi-Lift. I did this before tucking the tails (ends) of the knot.
    setting knot.jpg

    5. The tails of the knot are tucked back inside the rope, which effectively increased the rope diameter in this section. This increases the bending radius of the eye, which improves knot strength (and therefore shackle strength)

    20170122_160227.jpg

    6. :beer:

    7. I bought some 1.14" ID nylon protective hose sleeve on Amazon, doubled it over for 2x thickness, and slipped it on for chafe protection.

    8. I ended up making a couple. This version has estimated 230% breaking strength of the 24,000 pound single line, so around 55,000 pounds total. I would not use this for shock loads (snatch straps), but would be great for winch line extensions and other riggings. 2 shackles.jpg

    Cheers.
     
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  2. TheForger

    TheForger

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    Keep us updated as to how well they work for you
     
  3. John McVicker

    John McVicker SILVER Star

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    Subscribed, I like this.
     
  4. half k cruiser

    half k cruiser

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    Its a bit creepy not seeing the tail of the not. With knots like the bowline, EDK, and even the family of 8's that tail is your safety factor.
     
  5. beachboyy

    beachboyy

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    I made one the other day also out of some 3/4" dynex dux I had laying around. It's pretty big but will come in handy. Wondering why you would shy away from using them in shock load situations? I understand there is no (very little actually) stretch but as long as your using a kenetic rope (nylon etc) with it they are fine with shock loads. People use d ring shackles in those situations all the time and these are expenentially stronger. I haven't done the calculations on what he breaking strength of this 3/4" shackle is, but it's ridiculous.
     
  6. beachboyy

    beachboyy

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  7. cartercd

    cartercd SILVER Star

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    Half k cruiser: Although you can't directly see the tails, you can feel them as they extend about 5 inches below the knot and inside the shackle. So before put into use, you can essentially check that the knot is not pulling through. Once put into use, it seems the failure mode is not so much that the knot pulls through, but either the eye breaks or the line breaks just below the knot.

    Beachboyy: Most 3/4" shackles are rated at 4.75 tons = 9,500 working load limit. I looked up a Van Beest (highly respected brand) spec sheet and they list safety factor as 6:1. So this would imply breaking strength of 57,000 pounds for a the 3/4" Van Beest, very similar to the 55,000 pound (theoretical) breaking strength of my 7/16" Dyneema shackle with button knot. I only hesitate to use soft shackles for large shock loads as the manufacturer (Sampson Rope) indicates shock loads may weaken the rope over time. Probably not an issue if you are employing a large safety factor and not frequently abusing the shackle. Of course, a failure with a completely soft rigging system is not as dangerous as flying metal. Sampson rope info below.

    as sampson rope.PNG e
     
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  8. stock

    stock SILVER Star

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    We do this on ships all the time. That eye splice is the strongest possible. The rope will break before the splice. I'm hanging from an eye splice.

    20170328_064757.jpg
     
    Last edited: Mar 28, 2017
  9. half k cruiser

    half k cruiser

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    @stock sweet boat. Yours ?
     
  10. Zjohnsonua

    Zjohnsonua

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    Looks like this one went quiet, but I'm sure I'm not the only one looking at soft shackles these days.

    Sized appropriately, I'll take an equivalently load rated soft shackle over a steel one. Reason being that in shock load situations the rope will eventually fatigue and break, but so will the steel one. Yet the soft shackle will fail safely, while the steel one turns into a high energy projectile. All rigging materials have a limited number of shock loadings. Nothing should be expected to last forever.
     
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