Union 36' Chainplate Replacement

[shellyciszek]

Hello All!
I have just bought the steel to replace our chainplates on our Union 36'. We will be moving them to the outer hull. The old ones are glassed in, and there is rust coming out of the bolts! The problem is that the chainplates are hidden behind beautiful teak cabinetry, and it will be such a shame to have to remove it or harm it in any way. I had to remove some on the starboard side to reach the water tanks, and the amount of epoxy and bronze screws used made it near impossible not to damage it. I am wondering if anyone else has done this, and how. I read one blog of a guy saying they didn't want to touch the teak, so they left them in place... Sounds fantastic, but how the did he remove the bolts? And ideas would be much appreciated.
Thank you!

[Orion Jim]

Adding external chainplates is not as simple as it appears at first glance. Boats with external chainplates routinely have extra layers of fiberglass radiating from the attachment points to spread the stress to a large portion of the hull. Similar to the extra layers of sailcloth at the clew, tack, and head of a sail.
I presume this has already been taken into consideration.

[model 10]

What I did, cut the old plates off flush with the deck and bolted the new external plates to the old embedded plates. I used a hole saw on the inside wood to expose the nuts.

[shellyciszek]

Orion Jim-
That was not taken into account. We thought we would leave the existing chain plates where they are and use them as backing for the new ones, because they have horizontal tabs that are fiber glassed into the hull as well. You think moving them to the outer hull would need more hull strength? I don't see this being an issue, as the chain plates that are in there now are fiber glassed into the hull and we are moving them a half inch to the outside, but using the same hole pattern and everything. What re your thoughts...
I like the suggestion of using the hole saw to uncover the bolts. I will try that. Do the new chain plates need to be thicker than the in hull ones? I have read about people going from 1/4" to 3/8" when moving them. Is this necessary?
Thanks

[rbk]

If your knees aren’t rotted out I would worry about reinforcing the hull either. If they’re rotten they’ll need replacing but can be done to the interior. As for access, just as mentioned above with hole saw or cut 1/2-3/4” around your plates with an oscillating tool then cover with a wood cover plate finished similarly in teak, oak, mahogany or whatever. You can also leave exposed and finish the hull around the opening in a vinyl headliner material or paint to keep it looking finished but allow unimpeded access for inspection.

[Jim Cate]

We thought we would leave the existing chain plates where they are and use them as backing for the new ones, because they have horizontal tabs that are fiber glassed into the hull as well.

This plan sounds completely feasible to me. I see no loss of strength, for the loads will be absorbed in the same manner as in the original setup.

New bolts out of at least 316 s/s and better 2205 s/s or titanium, and it will be good to go.

And the various suggestions for hiding or disguising the access holes are excellent, so pick the one that best matches the surrounds and tickles your fancy.

Jim