Two years ago I straightened out my anchor chain by letting it hang straight down without the anchor. After two seasons of use it was again badly twisted. Since we rarely spend more than a couple of nights in the same anchorage, and we only anchor out perhaps 20 times a year, it was hard for me to beleive the twist was coming form just the swinging of the boat at anchor.
I decided to troubleshoot the issue in a methodical way, and figure out the exact cause of the twist.
I began by removing the anchor and dropping all the chain in the water at my moorage slip. As it went out I untwisted as much as I could by hand. Then I began pulling it in by hand using the manual handle on the windlass. When using the motor it moves too fast to see the movement or twisting. I notice that even though I centered the chain in the rollers, it rode off to on side after pulling it in a few feet. The I observed the chain flop over as it fell of the side of the roller toward the middle, introducing a twist. This was an important clue, but I thought the chain was riding up one side because the boat had somehow moved since I dropped the chain.
It would take a very long time to pull the chain in manually. I gave up and used the motor. It jumped, but now I could see the chain flipping on the first roller as it came in.
The next day, I took the boat out into deep water an dropped all of it straight down, except the last few meters. I then secured it with the chain hook so I could untie the safety line and straighten the remaining chain before retying it. Then I again started pulling the chain up by hand.
Even with the great weight of the chain on the roller, it still rolled up one side and flipped over.
It had to be the shape of the roller that was causing the twist. Sometime in 2022, another boat hit my anchor while maneuvering in the marine. I don’t know which boat, because it was a while before I noticed the damage.
The anchor was rammed back so hard the axle was bent, and the side plates were bent inward. I removed te assembly to repair it. I had to cut the old roller and axle in order to get it apart.
The old roller had a straight center with a chain groove, and straight V sides. The new one had concave sides. This seems to be where the chain rides up. The groove is quite wide, probably made for 3/8″ chain.
I am going to make a new roller, designed to keep the chain from rolling. Reader suggestions for the best shape are welcome. The illustration below, from a Cruising World forum, indicates what I have in mind. However, I am worried that it might jam chain if it is too tight, and I think the curved side slopes may flip the chain if it rolls out of the groove. Reader input is welcome. Leave a comment if you have a helpful idea.
My theory is that this roller is designed wrong. The rounded but shallow groove does not fit the chain well, and the concave shape on either side does not allow the chain to sit flat. The chain rolls out of the groove and flips half a turn. Result twisted chain.