Here are instructions for making for a BB soft shackle and a rough guideline of measurements. It makes a generous sized shackle of about 60x line diameter, which is nice for handling in 5 & 6 mm line, the two most common thicknesses we are using. I also think that a longer shackle length like this helps with load distribution, which is beneficial. This is about the length I have been making Better soft shackles for general use.
You could shorten this if you wanted by shortening the amount of central bury and/or shortening the tail bury (I would not shorten the tail bury to any less than 10x line diameter, as it needs to tuck in neatly). Lengthen by lengthening the central buried portion. Strengthen it by increasing the bury of the tail to approximately 30x line diameter (estimate).
This has not been load tested (is anyone able to do this?), but I am guessing it should be at least the same strength as a Better soft shackle, if not a bit higher.
INSTRUCTIONS FOR THE BB SOFT SHACKLE
Z = Amsteel Blue diameter
(units don't matter, as long as you keep them uniform; working in mm is much easier than in inches)
Finished shackle length from tip loop to base Button = 60 Z
Approximate amounts of line needed if using 4-8mm Amsteel:
Very bare minimum (use only if you are skilled with the button) = 220 Z
Amount if you are reasonably comfortable with the button = 230-240 Z
Amount if inexperienced with the button = 250 Z
- Tape the ends of the line to stop them unravelling while you work.
- Find the halfway mark
- Measure 7 Z from this and squish the line together to open up the weave
- Using a marlin spike (I find a fid too sharp for this), poke a hole cleanly through it a little below this point leaving 6 strands on each side and making sure none of the strands are snagged. This hole is B.
- Poke the longer end of the line through B. A fid helps, but is not essential for this step.
- Insert 4 lines through the loop and tighten up the loop lightly around them
- Tape the two lines together near the loop to secure and remove the 4 lines. The tip of the loop is A.
- On the longer line mark 15 Z from A. This is C, the entry point of the fid
- Measure 35 Z from there. This is D, the exit point of the fid
- Insert the fid into the entry point of the longer line, with the shorter line fed into the fid, and feed it though to the exit point
- Pull through the line and milk the cover down firmly. The outer covering over the buried portion will enlarge and end up shortening the final buried length to about 33 Z
- Measure 15 Z from the exit point and tape the 2 lines together firmly with the edge of the tape at the 15 Z mark. This is E and where the base of the Button will sit.
- Mark the working ends at their tip so that they are the same length. This enables you to check if you are tightening the Button evenly
- Tie the button and snug up evenly and reasonably firmly. Step by step instructions for the Button are in posts 4-20 of this thread:
Instructions for Tying the High Strength Soft Shackle & Button Knot
Tighten up the Button:
- Using a Marlin spike and starting from one standing end at the base move anticlockwise and tighten as hard as you possibly can by pulling on the spike.
- Repeat with the other standing end and make sure the length matching marks on the two working ends indicate an equal length
- Remove all the tape
- Poke the loop and working ends through a suitable washer (13mm inner diameter with just hold 6mm line) and pop under the jaws of a vice, leaving the jaws a little loose so the line can move freely.
- Insert a rod into the loop and pull up as hard as you can on the two standing ends
a working end around a rod and pull as hard as you can
- Repeat with the other working end
- Repeat the last 3 steps
Bury the working ends:
- Each working end will be fed into the standing leg immediately clockwise to it when looking down on the head
of the Button. This will tuck the end into its corresponding standing portion.
- Insert a marlin spike between the strands and into the core
of one standing leg as close as possible to the base of the Button and create a clear opening by gently wriggling (try not to snag any fibres)
- Insert the fid with the correct line fed, feed the fid through the core
and exit at the edge of the long buried portion and pull the line through
Milk the cover firmly and mark the end of the working line
- Pull on the working line to expose it again, cut it off at the mark and taper the end third evenly
- Milk the cover over it
- Repeat with the other working end
Pretension the shackle:
Evans Starzinger recommends applying load to a soft shackle and leaving it for about 20 minutes to pretension the stopper and improve strength.
I have no Dyneema
left, but next year I am planning to makes two lengths up with eyesplices on each end, one eye just big enough to feed the loop of the soft shackle through and snug it up against the button. Two are required to make sure the load on the Button is symmetrical. Line can be connected to the loop of the shackle at one end and the two eyesplices at the other end and then tightened between two winches (one can be secured to a cleat/bollard if you have a sufficiently strong one).
Anyone with a better idea of how to pretension?
That's all folks