The Offshore Voyaging Reference Site

A Better Chain Plate


While thinking about how to make the Adventure 40 an incredibly trouble free and reliable ocean voyaging boat, I have worried most about two areas: chain plates and the rudder.

Both for the same reason: they are the area in conventional fiberglass production boat construction where stainless steel and fiberglass come together in the presence of salt water to make an unhappy marriage.

Let’s leave the rudder aside for this post.

Stainless steel chain plates, particularly if they are set inboard and poke up through a slot cut in the deck, will, if the boat is sailed hard offshore, eventually leak, usually within a few years of launching, sometimes much sooner.

And once water gets in, the chain plate itself starts to corrode—a problem that is serious enough that any boat so built that is more than ten years old should have its chain plates carefully checked, and after 20 years replacement is often the only safe alternative.

Yes, I know, there are a lot of different ways to try and leak-proof a stainless chain plate. Some of them even work for a while. But the facts are that as long as you are mixing two different materials with radically different mechanical properties and trying to keep water from getting between them, things are probably not going to go well in the long term. Something to remember when refitting a boat—teak decks, or any wood trim for that matter, come to mind.

One of the very cool things about metal boats is that the chain plates are made of the same material as the hull and are bonded to it by welding, thereby avoiding leaks and other problems for many decades.

I want to do the same sort of thing with the Adventure 40, and Matt Marsh, engineer and all around smart guy, with a lot of hands on experience with fiberglass, makes a very convincing case that we can do just that by making the chain plates part of the hull.

One option would be to build the composite chain plates outside of the boat from pre-preg materials over a mold and then bond the resulting assembly to the hull and/or bulkheads, as well as the deck, with epoxy or Plexus adhesive.

I’m pretty sure this would work well since a friend of mine made a lot of complex fittings, including a goose neck, in this way, very quickly and inexpensively.

And I have another friend, one of the world’s most experienced composite boat builders, who assembles the high tech boats he builds with Plexus and says that the resulting bonds are stronger than the laminated assemblies they connect.

By the way, I’m not the only one who does not like stainless steel chain plates. The new Navy 44s have composite chain plates because of the intractable leaks that the older generation of boats suffered from.

A Campaign Against Stainless Steel?

And if you are beginning to think that I have a “tude” (Bermudian dialect for attitude) against stainless steel, you would be right. I think that we yachties put far too much trust in the material and often use it, just because it looks shiny and strong, when other materials like good quality bronze, galvanized steel, aluminum, or composites would be better and more reliable.


If you have solid engineering knowledge or first hand experience that will help us solve this problem in a cost effective way, both for the Adventure 40 and chain plate replacement in older boats, please leave a comment.

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