Soft Shackle Variation #3
Ring Hitch Soft Shackle
This new variation on a soft shackle uses a loop instead of a diamond knot on the main part of the shackle so that it can be attached to eye spliced jib sheets. A second stopper loop with a diamond knot is permanently secured to the clew ring. Although the bury length of the spliced loop on the shackle is short, the way it is secured around the jib sheets caused high compression forces that hold it together. The loop goes around the eye splices in the sheet ends. This holds them together and makes the shackle operation separate and easy as the shackle is aligned straight and you don't need to milk it around a curve
This is a close up of the cross over and the lock stitch.
Test Results
The test was done with a scale model using 1/8 Amsteel and a double loop of 3/8 Yacht Braid to simulate two sheets.
The test stopped when the 3/8 yacht braid broke. It was old yacht braid, but there was a lot of force on it from the hydraulic jack. I then substituted some new 1/2 inch 12 strand poly braid and pulled until the diamond knot stopper loop broke. This is the same failure as a standard soft shackle so this shackle has a strength half the strength of a normal soft shackle which splits the load between its two sides. Estimates vary as to how strong that is with conservative estimates indicating 60% of line strength to others indicating 80-90% of line strength. If you need a stronger solution, use the next size up for the diamond knot. My estimate is that this is 80-90% of line strength. Here is a video of the test.
Further testing was done on a variation of this variation using 7/64 Amsteel to allow it to be taken to failure with a 35 power Barient winch. The goal of this test was to stress the loop. For this test the shackle was attached to some 7/16 yacht braid without the ring hitch, just putting the yacht braid through the loop with a bowline. This put maximum stress on the splice. The question was would the splice with only 23 diameters of bury pull out or hold. The failure was still in the stopper loop, not in the shackle itself. The picture below shows the variation of the shackle and the failed stopper loop on top.
The final test did use the ring hitch to attach the shackle to the yacht braid. I used a 5/32 stopper knot to eliminate that as the failure. The shackle loop did not slip. The failure was at the eye of the shackle. The new 7/16 XLS line was stretched about 17% before the shackle broke. The force to break this was between 2000 and 3000 pounds. The shackle is clearly stronger than line strength. Using a stopper knot from the next size up material will increase the strength of the overall shackle and probably exceed the line strength of the line the shackle is made of.
Howto Make Them
Soft Shackle Variation
Follow the instructions in the Soft Shackle Howto up to the point where you are going to make the diamond knot. Instead of making a diamond knot, make a mark 45% from the end of each tail piece. Thus, for 3/16 line with 10 inch tails, mark 4.5 inches from the end of each line. Starting back about six diameters, mark a left and right hand strand. Mark every other one going away from the end for a total of six (3 right-left pairs). Pull these and cut them off. Then bury each tail in the other tail at the mark and feed back toward the body of the shackle. Pull the crossover tight, then smooth it all out. Lock stitch on each side of the bury as described HERE.Variation shown in test above
The variation above is shorter and easier to use than the main one shown in this write up. To make a minimum length one scale my dimensions from the 7/64 line by the ratio of the line diameter. For that I used 18 inches of line. I did an eye cross through near the center then went back enough so the eye opening would clear the stopper knot, about 2 1/4 inches for the 7/64 line. At that point, I put one line through the other, then again with the other line as in a Brummel splice, then again passing the first line through the second. This completely locks the shackle part of the line. Use a dimension for the tail as explained above.Stopper Loop
Using the calculator from the Soft Shackle Howto, measure off a piece twice the length of the first mark. Double the line over, tape it at the fold, and tie a diamond knot using the two ends. Lock it by placing the ends in a vice and pulling on the loop with a lever of some kind. I use a hammer with the had as the fulcrum and the loop on the handle near the head.How to Use Them
Loop the soft shackle variation around eye splices in the sheets.
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