Fitting Shackles to your Anchor
From Laurence Burgin, master mariner and safety expert – get the anchoring right!
We’re writing this because we notice a lot of people replacing their anchor shackles with stainless swivels.
Let’s analyse the reasoning behind this.
Anchor shackles need to be secured good and tight. Use a large spanner to fit the pin and wind it as tightly as possible. If using Allen drive pins, use an Allen drive socket or extension tube on a key. Most swivels have Metric drive pins. Lock tight the threads and if a le, size the pin with wire. Allen drive shackles in bow and D-shape are a good solution when snagging is a problem with narrow bow rollers, as found on many sports boats. Use high strength thread lock compound with Allen drive shackles. Check the shackle regularly.
There is still a lot to be desired in the shackles and swivels on the market but I believe that even though not passing the load test high enough it is better with a good shackle than a bad swivel.
Swivels
Swivel bolts should ALWAYS be fitted with thread locking compound on thread. This will prevent a potentially disastrous failure with the pin unscrewing due to rattling on bottom, leaving anchor on bottom and boat adrift.
It has been found that many swivels catch on the edge of the bow roller and because of this it has been a point of interest for safety, product liability, appearance, load test, fixing bolt systems (there are several versions), polished or satin finish, load test labelling, branding, chain size, swivel pin size and fixing method, to find something to prevent this.
Because of our research we now always fit a shackle to the anchor first so the swivel can articulate sideways. In extreme side loads, the swivel can break if connected directly to the anchor. This has happened recently in the harbour. This would not happen with a bow shackle fitted first. A swivel will slide to the side and be end loaded, not side loaded.
As a general rule, fit the same size shackle as the chain, e.g. 6mm shackle for a 6mm chain onto a 4, 6 or 10 kg anchor. Sometimes two shackles need to be sued to achieve a correct connection. If that is the case use a larger shackle through the anchor then a small one to the chain. Different sized shackle ‘throats’ need to be considered to match the width of the anchor stock. D-long, D-wide, D and bow shackles are all options depending on the setup. Twist shackles are sometimes used but can distort under load.
Bottom Line – Always use quality shackles whether stainless or galvanized. Large boats should use high rated shackles.
