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Releasing the shackles ... We’re talking about soft attachments!!

Soft black attachments, rope shackles, loop blocks.....all terms that are becoming more common in sailing hardware. If you look through every block manufacturer you will find their solution to the soft attachment block. This isn’t just a fad but more a movement inspired by the innovation in racing teams being passed down through production boats to being available to the general public to use on their Westerly Fulmar.

Ubi Maior RT55V

When you look into it with out prejudice or fear of innovation you find that many of the soft attachment blocks pack more kilos for your pounds. This is often due to the particular block actually requiring less parts. Metal ones anyway. The more kilos comes from the way the soft attachment, be it a loop or a lashing, is attached to the block. More often then not it is actually easier to build a block where the load securing method is through the centre of the sheave. This negates the need for structural side plates and lots of FEA (finite element analysis) to make sure your block stays together. With the loop going through the centre of the sheave. All the load is directly onto the sheave and bearing. This is also great from a reliability and safety point of view. Even if the block “fails” the loop is still going through the rope that is running round the block so it can’t actually go anywhere. But beware as just because someone advertises it as a loop block it doesn’t mean the aforementioned method of construction has been used. Some manufactures will simply make a small change to where the shackle would normally attach that allows for a soft shackle to be used meaning the body of the block is still doing all the work and the failure redundancy does not exist in these cases.

The use of soft attachment blocks has a knock on effect at the other end of the loop where it attaches to the boat. Again designers in an effort to reduce weight and utilise the materials and structure they are working with are coming up with clever ways to utilise this attachment method. This is something you will see on every new race boat but now we can start to see it moving into production boats.

And just for a bit of padeye porn, here is one on the IMOCA 60 Hugo Boss utilising the through deck soft attachment method.

More on padeyes to following in another blog....

So back to soft attachments and now including textile loops. The long and the short of it is that now we have these amazing new rope products like Dyneema that are stronger and lighter then steel we don’t have as many places for metal shackles and that is also then changing the way designers and manufacturers build their boats. That’s not to say that there aren’t places that only a shackle will do. You’ll be hard pushed to make a midrange mainsail traveller system without shackles. And some boats still have traditional stainless steel chain plates for backstays etc. that you just can’t not use a shackle on.

With the addition of a dogbone in a strop they can be as functional as a normal shackle allowing blocks and ropes to be attached with ease and with out the associated damage that shackles can cause.

With more and more composite spars being used in production boats the need for soft attachment blocks is increasing. When designing composite structures you consider all the forces being exerted and where possible you try and spread the forces to reduce the amount of carbon and therefore weight required. Single points of attachment such as the tangs under your boom point load the composite and require more reinforcement. Soft attachments in the boom example would go around the entire boom spreading the load and using the existing structure of the boom to hold the force. This concept really is the driving force in modern design.


It may require a bit more thought then the old days when you just shackles blocks to ropes or chainplates and added a bit of seizing wire fire security. But if you consider the whole system you are making and what you are attaching it to you can produce a nicer, lighter, stronger and more reliable arrangement that won’t break the bank.

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For help with this or advice on what block to use get in touch with Racetec at info@racetecrigging.com or call us on 023 9298 3191 to discuss.

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