PS Advisor September 2018 Issue

What Chain Connector Will Fit My Gypsy?

Regarding your recent article on joining chain segments (see “Reliable Chain Connections,” PS June 2018), I’ve been coastal cruising from Canada to Panama since 1983, and continuously since 2005. I have wondered about using a single 5/16-inch shackle, which will connect two lengths of 3/8-inch, G-43 chain. The Crosby top of the line 5/16-inch will go around the gypsy pretty well. I tried it, but I am reluctant to use it. Any thoughts?

William Nokes
Someday, Gulf Star 41
Puerto Madero, Mexico

Your reluctance is warranted. The maximum size of your anchor shackle is limited by the size of your anchor-chain links. Typically, you need to go up one size greater than the nominal size of our links—i.e. your 3/8-inch chain can take a 1/2-inch shackle—to match the working load limits for G43 chain, and this over-sizing is recommended for lower tensile strength G30 chain as well.

galvanized g-100 omega link
Jonathan Neeves

A galvanized G-100 Omega link is used to connect high-strength G-70 chain to a properly matched Grade-B screw pin shackle. The chain and Omega link have been Galvanized using Armorgalv.

When matching shackles and chains by using the maker’s published working load limits (WLL), confirm the safety factor used to determine the working loads. Multiplying the WLL by the safety factor provides a minimum tensile stress, which is a closer approximation of ultimate tensile strength (UTS, see “Anchor Shackles, Round Two", PS October 2016; “Making Sense of Chain Standards,” June 2014; and Inside Practical Sailor Blog, “Tips on Choosing and Sizing Anchor Shackles”).

Be aware that manufacturers often use very different ratios for calculating safety factors for chain (3:1 to 4:1) and shackles (4.5:1 to 6:1). One reason for the higher safety factor for shackles is that side-loading a shackle can dramatically reduce its strength. According to warnings posted by several manufacturers, a 45-degree side load can reduce the shackle’s rated strength by 25 percent, and a 90-degree load can reduce it by 50 percent.

For chain rodes, we generally recommend the largest possible Grade B shackle be paired with proof-tested G30 hot-dipped galvanized chain as the most reliable and cost effective option. You, like many boaters, have opted for higher strength G43 chain, which is stronger, but also more expensive.

Unfortunately, the smallest Grade B shackle that we’re aware of is 3/8-inch. You would then have to opt for a lesser-grade 5/16 Grade A shackle (yes, Grade A is inferior to Grade B), and this would be weaker than your G43 chain.

In our testing, we found several 3/8-inch shackles that should fit common 5/16-inch G43 chain (11,400 lbs. nominal breaking strength) and afford some confidence, even when side loaded. For example, a Crosby 209A 3/8-inch Grade B shackle with a 4.5:1 safety factor (4,400 lbs. WLL, 19,800 lbs. UTS) would match the strength for 5/16-inch Peerless Boatman’s Pride G43 chain with a 3:1 safety factor (5,400 lbs. WLL, 16,200 lbs. UTS). But, as you are aware, this shackle will not fit your gypsy.

A connecting link or C-link might pass through your gypsy, but again, Crosby 3/8-inch connecting links or “missing link” joiners do not match G43 WLL. A Dyneema soft-shackle would appear to match strength, and will probably go through the gypsy with ease, but we worry about abrasion.

Another option is a 10 mm G100 Omega link, which has a WLL of 8,800 pounds, but is a semi-permanent connector. For a permanent solution, the link would need to be galvanized, which will reduce WLL to 6,600 pounds. If the Omega option is of interest, you can try Spencer Industries in New Jersey, which uses the Armorgalv process to protect the US military equipment. It may have some 3/8-inch (10 mm) Omega links.

All of this again raises the problem of upgrading to a smaller-size, higher tensile strength chain.

Comments (4)

Regarding the best way to seize shackles, I've had stainless wire get pinched and broken under load. For the past five years I've been using 3/16 uncovered spectra line, tied in a square knot and locked with superglue. I use two such lines on each shackle pin for backup. If the spectra gets pinched it spreads out rather than breaking. You have to watch out for UV exposure, so I change them every few seasons. Cut them off short with a hot knife. Works very well.

Ken
S/V Eagle's Wings

Posted by: KenC | September 6, 2018 6:25 PM    Report this comment

I realize the emphasis of the article is the chain connector, but think the picture should also show, and article should include recommendation that stainless wire be used to prevent the connector from unscrewing. If that happens the size of the connector won't matter. Just an observation.

Posted by: Jstew | August 18, 2018 10:22 AM    Report this comment

I realize the emphasis of the article is the chain connector, but think the picture should also show, and article should include recommendation that stainless wire be used to prevent the connector from unscrewing. If that happens the size of the connector won't matter. Just an observation.

Posted by: Jstew | August 18, 2018 10:21 AM    Report this comment

Academic, but another reason for needing a shackle of heavier gauge than the chain is that the shackle cross bolt is probably subjected to worse stresses than the chain links, because it spans a wide opening and has to take the load as a beam, whereas chain links are shaped in a way that makes their loading more nearly just tensile.

One time I needed to swap a longer chain onto a chain fall in order to do a higher lift than it was made for. Sent my wife to the hardware store with link pitch and dimensions. Remarkably, she came back with chain that fit the sprocket very well. (We were in Norway and the chain fall was Japanese.)

The only thing that didn't fit was that the link stock was slightly thicker, so the internal dimension of the links didn't quite clear the clevis pin of the hoisting hook that I needed to swap onto the bottom end.

The interference was only a few thousandths, so I took a chainsaw file and opened up the bottom link by that amount.

My helper, a fellow Texan, drawled, "I always like to file a little thickness off my heaviest-loaded part...."

Posted by: Crispin Miller | August 18, 2018 10:15 AM    Report this comment

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