Chainplate Replacement Advice

[roverhi]

My chainplates are/were 1/4" x 1 1/2" x 12" or so with three 3/8" bolts to attach them to whatever they were anchored to below decks and 1/2" holes for the pins on deck. Stuck with 1/4" because that's what the boat had come with originally and were plenty strong. Ordered 1 1/2" flat bar stock in 316 from a metal supplier, can't remember who, and they sheared them to length. The material wasn't all that expensive, around $200 IIRC. Del drilled the holes, rounded off the ends and polished them for me. I could have done the job myself with a cheap drill press, cobalt bits, cutting oil and a grinder but Del did a much nicer job of it than I could have done. I did cut the old chain plates shorter, drilled larger holes and used them for backup plates for the new CP"s.

Might have gone with Titanium if I could have found the material reasonably. Old plates lasted more than 40 years which is way longer than I'll be around to enjoy the new SS plates. Actually wanted to go with bronze but couldn't find manganese bronze except in round bar. Only flat bar stock with suitable specs. around was aluminum bronze. Seemed to have all the strength, etc, of Manganese but couldn't find any information or opinions on its suitability for chain plates.

There is not a problem with galvanic corrosion on the rigging between dissimilar metal unless your boat spends most of its life under water. Bronze turnbuckles have been and still are the best for rigging screws. Have been used with stainless terminals and wire without issue.

[Nicholson58]

I can't tell you the peace of mind I got knowing our plates posed no risk. Makes you want to crank everything up.

[Stumble]

Originally Posted by tominny

But what about galvanic corrosion between dissimilar metals, i.e. stainless rigging and titanium plates?

A G5 titanium-316 joint causes lower galvanic corrosion dammage than a 316-316 joint. The FDA spent a lot of money researching galvanic corrosion inside the body, and the lowest corrosion joint was titanium-titanium, followed by titanium-316, then 316-316.

[Nicholson58]

Originally Posted by Stumble

A G5 titanium-316 joint causes lower galvanic corrosion dammage than a 316-316 joint. The FDA spent a lot of money researching galvanic corrosion inside the body, and the lowest corrosion joint was titanium-titanium, followed by titanium-316, then 316-316.

I'm not worried and the OP will be fine using 316L. My Ti-316 joint is above the deck, where I can see it. My Ti plates will never fail and I never have to inspect the below deck and through deck interfaces. On our boat, that means major dis-assembly of the cabin. I am totally glad to have the job completely behind us.

The point for the OP is that he has identified a point of failure that needs attention. For what its worth, the age of his boat pretty well brackets the problem. Nothing new here at all. Just glad he has determined to fix it.