I do not use a swivel. Most of the time a simple shackle is fine. However, on rare occasions the chain can become twisted when lying at anchor.
To put a twist in the rode
, the boat does not have to swing around the anchor, it only has to spin through 360°. The most common situation I have encountered this problem is in weather
situations where there is two opposing wind systems. For example a southerly breeze with a local northerly sea breeze. In these situations the boat can do multiple spins in a short space of time as one or the other wind predominates.
At anchor the twists in the chain are not noticeable because they are distributed over the whole length of the rode
. However, when the chain is retrieved, the gypsy
will not pass the twisted chain so the twists become concentrated in the ever shortening length of chain between the gypsy
and the anchor. Chain will only accept a certain number of twists per meter before it starts to hockle.
The torque can be very impressive. On one occasion I was concerned the chain links would be permanently deformed. Once the anchor has broken free the twists will spin out even without a swivel (sometimes very dramatically). But to break out a good quality modern anchor the scope
has to be close to 1:1. If the twists become excessive before the rode can be shortened to this scope
, the anchor cannot be broken out.
Fortunately, this is very rare problem. I have experienced this issue less than 1 in every 1000 nights at anchor. However, it can be very frustrating to solve and the torque in the chain is potentially quite dangerous.
Not a great photo
, but if look carefully you can see the chain start to twist severely. There are even a couple of links lying sideways even though the rode is under a lot of tension.