Soft Shackles

A Different Way

Edit: at the end of this article is an update on the performance of these soft shackles after about 4 years of use.

For some time I have been fascinated by soft shackles, there are many styles and ideas but I think this soft Shackle – a different way woks well when the shackle is open and closed regularly. What ever style of soft shackle utilised I do like them on yachts for a number of reasons including:

  • They’re soft
  • They don’t do much damage when they hit things
  • They’re smaller than a bowline that they may replace (Especially on head sails) and are far less likely to tangle or get hung up somewhere around the mast during tacking or gybing
  • They tend not to undo
  • They tend not to release
  • Just about anybody can fasten them quickly (Compared to a bowline).

For a number of years we have been using soft Shackle – a different way on our head sail sheets, the sheets have eye splices so it is not really practical to end to end them to spread the wear, but we have been using the same sheets for nearly four years now and they are showing no sign of degradation or damage. We do look after them fairly meticulously, washing them in a eucalyptus based detergent every few months. (As we do with most of out lines).

Something that annoyed me with most soft shackles that we have used is that they a made from single braid Dyneema (or equivalent) is that a while the line becomes a bit furry, the continual opening and closing seems to break down the plaiting, they just become a bit nasty and get a bit hard to use. I thought that there had to be a “Different way”.

Soft Shackle a different wayWe have been using soft Shackle – a different way on our head sail sheets for about twelve months and they are still working perfectly, and showing no sign of degradation, I have just made a new pair as I noticed last evening that the girls were having a bit of difficulty releasing them, the problem being that they are a bit short and do not allow the user to get a good purchase on them to open the captive slider. the new ones are about twice the length so hopefully that will make life a bit easier.

The original shackles were deliberately made short to avoid them entering the head sail traveller bock, but on reflection as long as the stop knot is at the sails clew this will not be an issue.

These soft Shackle – a different way are made 6 mm polyester covered dyneema, the capture loop is made by looping 1.7 mm dynice in a figure 8 pattern, one side is attached to the dyneema, but only at each end of the loop allowing for some balancing of the load over the entire loop set. The other side through which the dyneema is free to run has some sneaky weaving to stop the loop set from separating during tightening and/or releasing. At  the other end the stop knot is a simple diamond knot with the loose ends merely heat sealed.

When I read any discussion about soft shackles there seems to be an obsession with strength, my view is that they only have to be as strong as any suitable apparatus that they replace. We use 10 mm spectra sheets. which I understand has a breaking strain of around 4900 kg. put a bowline at the end of it and that strength will drop to somewhere to around 2500 kg. While these shackles have not been tested a reasonable assumption is that the 6 mm Dyneema which has a breaking strain of somewhere around 1700 kg and general contention is that a soft shackle about doubles the breaking strain of the base line, if we assume that these shackles only increase that load by 75% that will give them a breaking strain of about 3000 kg. right in the same ball park of a 10 mm line with a bowline. The looping is made of 1.7 mm dynamic which has a breaking strain of about 240 kg. there are six loops that are balanced, if were to conservatively estimate the loop set would provide say, 240 kg times 3 then the loop set would hold upwards of 720 kg. The actual lateral loads in this area of the shackle would in reality be very minimal.

The only down side to these shackles is that they take a lot longer to make than the standard styles. The up side is that in 12 months racing on average, probably more than once a week and a lot of cruising in between we have not had a single failure.

Instructions for tying the knot (Known variously as a lanyard knot or diamond knot) can be found on the excellent animated knots site,

There are many ways of creating a soft shackle, this is one that I may be the creator of, there are many others, I would recommend having a look at a great resource on a lot of things sailing with a few articles on soft shackles.

Elan 340 G-whizz Soft Shackle Open
Soft Shackle Open
Elan 340 G-whizz Soft Shackle Lock end
Soft Shackle Lock end
Soft Shackles – An update

We have just retired the soft shackles on G-whizz’s head sail, after 5 years, over 500 hours of racing and lots of cruising , local in the harbour and a coastal. As an aside sailing was an approved exercise during the worst of the COVID action in our part of the world and we took advantage of it.

The reason for retirement was that they had become very stiff to undo, the 6mm dyneema would not slide easily within the 1.7mm dynice throat, I am not too sure if its shrinkage of the line, growth in the lines, build up of contaminations or whatever, it was time to replace them. I have left a bit more room in the throat of he new shackles and I wonder how ling they will last.

The actual mechanical performance and durability of the shackle has been most surprising  as shown in the following photos. Apart from a bit of “Furring” on the outer of the lock eye they look as good as new. Interestingly the compression of the line just below the knot at the lock illustrates just how the load tightens and locks the shackle.