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Swivels and anchor chain

Aug 28, 2012

To the editor: I have given the subject of how to attach an anchor to an all-chain rode much consideration on dark and stormy nights.

At first I simply used an ordinary shackle, but the problem with this solution is that the chain does twist in ordinary use and the anchor often comes up facing the wrong way to house properly in the anchor chute.

So I installed a fork/eye swivel to allow me to rotate the anchor to house in the anchor chute.

Norm Johnson inserted a swivel in his anchor chain to ease anchor recovery.

During more dark and stormy nights, I considered the fact that over the years I’ve heard and read that the swivel was the weak point in the system.  

So I went back to a hefty anchor shackle with the pin screwed in tight, the eye cut off and the threaded end peened over. But I still had the problem of the anchor coming up in a position that required me to rotate the chain so the anchor would house properly. The solution to this problem obviously required a swivel.

It seems there are two weaknesses to the swivel.  

1. The half-inch swivel has a safe working load (SWL) of 3,600 pounds, significantly lower than my half-inch BBB chain (4,500-lb SWL).  

To address the SWL problem I stepped up from a half-inch swivel (3,600-lb SWL) to a 5/8-inch swivel (5,200-lb SWL), significantly stronger than my half-inch chain (4,560-lb SWL). I connected the swivel to the chain with half-inch connecting links (4,750-lb SWL).

2. In addition, if the fork end of a swivel is attached directly to the anchor stock, and the anchor chain pulls at 90 degrees from a fully buried anchor stock, it stresses the swivel in a “break stick” manner making it even weaker.

To address the “break stick” weakness I cut the chain several links from the anchor and installed the 5/8-inch swivel several chain links from the anchor using half-inch connector links (4,750-lb SWL). The posts of the connecting links are peened over just like a rivet. I used a small oxy/acetylene torch to soften the connecting link posts then hammered each one down snug.

I feel much more secure now with that oversized swivel, combined with the flexibilty of those five chain links, keeping my anchor connected to the chain on those dark and stormy nights.

— Norm Johnson is a retired merchant marine radio-electronics officer who lives aboard his ferrocement boat Bandersnatch. Johnson has sailed the boat almost 40,000 miles, normally wintering in northeast Florida and summering in New England.

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