L-36.com
Home Articles Soft Shackles
Weather & Tide Sailing Companion Airport Forecasts (NEW) Tide/Current (Day) Tide/Current (Week) SF Bay Current Map
Manuals Used Sails
Technical Data Marine Resources Racing Resources @L-36 Top Videos L-36 Owners Roster Contact

Double Soft Shackle

Soft Shackle Variation #7

This double ended soft shackle is the 4th generation of a design that can attach to a pair of eye spliced jib sheets to the clew of a sail very quickly. The shackle is secure around the jib sheet prior to being "clipped" to the clew. This version is easy to make and has the advantage of a non-constricting hold on the jib sheets. There are links to the previous versions at the bottom of this page

The Shackle

s73

s72

s71

Overview

The shackle has two sections. The short section will attach to the Stopper Knot. That needs to be long enough to allow the shackle to open enough to pass the stopper knot thought the loop. I used 3 inches in the sample below, which is made from 3/16 Amsteel. The center knot is a fisherman's knot and what a bowline. The bowline is used to turn the second tail around so that the two tails can be tied in a diamond knot. The diamond knot and the associated eye form the shackle that is used to hold the sheets. The second eye is used to quickly loop over a diamond knot on a loop that can be secured to a clew ring with a luggage tag knot.

Testing

I tested this shackle with 7/64 Amsteel using a 5/32 stopper knot. The shackle broke at the bowline knot part in the center. One would estimate that this would make the strength close to line strength as the bowline knot carried 1/2 the load and typically a bowline is 60% as strong as the line. In Amsteel, it might be less than 60%, perhaps 40% which would give the shackle a strength of 80% of line strength. It is definately not as strong as the line as there was a test link of just the line in my setup. This result was a disapointment. However, on one of my tests I used a 1/8 inch stopper knot and that is what broke. From that result, I would expect higher strength than what I got. Before using one of these with significant load, more testing with calibrated equipment should be done.

CAUTION: Be sure to do your own testing before using these. Safety is your responsibility not mine.

Stopper Loop

Note: For maximum strength of the double soft shackle, use the next size up line for the stopper knot.

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 Make The Double Shackle

These instructions are for 5/32 Amsteel. They produced a shackle that was a little tight. These numbers worked great for a 5/32 Amsteel using a 3/16 stopper knot. The key is to pick a length that allows the eye to open enough to let the diamond knot through with the snugness you desire. Experiment a bit before building the shackle so you get the fit you want.
  1. For this shackle, I wanted 3 inch loop bodies. This allows the loop to be opened enough to go around the diamond knot. This turned out just right but a bit tight. I would add just a bit and make them 3 1/4 inch next time. That would add an inch to the line and 1/2 inch to the eye to eye distance.
  2. I used 42 inches of 3/16 Amsteel. Mark 1/2 way along the line (at 21 inches from each end). This is a reference mark and it should be in the loop of the bowline.
  3. Mark spots 7 1/2 inches apart with one mark 4 inches from the center dot. It is offset to allow for the fisherman's knot. Pass the ends through the spots as shown below.s74

  4. Tie the knot below. The shorter end is to the left. If you look closely, this is a bowline with the end passed back through one of the loops, the one that goes around the tree. s75

  5. Here is a close up of the bowline knot. s77

  6. Snug the knot up tight keeping the center mark as shown and making sure your target length is correct from the edge of the knot to the eye.s78

  7. Using the end that is passed through the bowline, pull it through a bit more than you want it to end up and tie the fisherman's knot as shown. This is the tricky part as you need to get this knot in just the right spot. It may take a couple of tries. You want this knot to serve as a stopper for the bowline and at that point to have the left eye just open a bit. Perhaps marking the line right where it exits the bowline with the eye just right would have helped. s710

  8. Snug it up and pull on the end to tighten it. Note that when it is just snug, the line to the left of the bowline is still too short. That is because the fisherman's knot will move to the right as you tighten it and that will make that line too long if it doesn't start out too short. As I said, this is the tricky part so make sure it is right.s711

  9. The best way to lock up and tighten the knots is to pull on the three parts to the right in this picture. Pull on each of the lose ends and on the right hand eye. Be careful to note the dimensions as you tighten. I use vice grip pliers and some 1/4 pegs in a 4x4 as a fixture to get enough leverage to lock up the knots. When they are locked, they get hard like a piece of wood when banged on a table.s712

  10. When you are done, the two eyes will be on the same length section.s713

  11. Tie the diamond knot in the two lose ends. Adjust the position of the knot to get the size shackle you want.s714

  12. Done.
Version 1
Version 2
Version 3

NOTICE: Some pages have affiliate links to Amazon. As an Amazon Associate, I earn from qualifying purchases. Please read website Cookie, Privacy, and Disclamers by clicking HERE. To contact me click HERE. For my YouTube page click HERE