PBO reader Rod Stuart wants to extend his anchor chain. Metallurgy expert Vyv Cox has this advice on joining chain links…
Rod Stuart writes: “What is the safest way to join two equal galvanised chain links (I don’t just mean for going through the windlass)? A fat shackle or one of the link imitation gadgets?”
Vyv Cox replies: “To some extent this depends upon the grade of the chain links that you’re trying to join.
“Strong shackles, for example the Crosby G-209A, have sufficient strength to be suitable for grades 30, 40 and 70, but the best C-links are only good for grades 30 and 40.
“However, there is more to it than this. The pin of a 10mm shackle will pass through the final link of 8mm chain but of course the eye of the shackle will not.
“The only way in which shackles can be used is to have two of them, preferably ‘D’ rather than ‘Bow’, back to back.
“A high strength alternative is an S-247 double clevis link, also by Crosby. This comprises a forged steel double shackle with alloy steel clevis pins.
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“Its strength is suitable for chain to grade 70, the highest used in anchor rodes. Select the size whose pins will pass through the chain link.
“My only comment is that the split pins that secure the clevis pins can cause serious damage to bare hands!
Crosby G-209A strong shackle (left) and Crosby S-247 double clevis link (right)
The Crosby G-355 ‘missing link’ is designed for joining chain links
“A Crosby G-335 ‘missing link’ has greater strength than the chain links for grade 30 and just about equals the strength of grade 40.
“Beware that the chain links sold in most chandleries come nowhere near the strength of the professional items.
“It is the only means of joining chain links so they can pass through a windlass. There is a great deal of information about these C-links on my website.”
Barry Parkinson writes: “You made a comment that the Chain Links you buy in a Chanderly are not as strong as the professional one, does this mean the Crosby G-355 is or is not strong enough for G4 chain. Link 50mm long x 10mm dia.
“Help is needed. I guess I should buy 100′ of new chain, not many shops in Tonga South Pacific sell this.”
Vyv Cox replies: “To clarify a little confusion in the question, the Crosby C-link (missing link) is the G-335. The G-355 is a shackle that, although very strong, will not pass through a windlass.
“A well made-up G-335 should be stronger than Grade 30 (G3) chain but will have a slightly lower MBL, Minimum Break Load, than Grade 40 chain according to my own test results.
“In practical terms this is most unlikely to make any significant difference to the reliability of the rode. Fracture of anchor chain is almost unknown and even stretching of the links, at about half the MBL, is very rare.”
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