Soft Shackle – A Better Way
For some time I have been fascinated by soft shackles, there are many styles and ideas but I think this soft Shackle – a better way woks well when the shackle is open and closed regularly. What ever style though 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 shackles 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). After 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 “Better way”.
We have been using that “Better 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 traveler bock, but on reflection as long as the stop knot is at the sails clew this will not be an issue.
These “Better way” Shackles 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 the 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 a 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.
While comments are not possible on this blog I would be interested in any comments that are posted via the contact form here. I will publish any comments.
G-whizz Elan 340