Chainplate/bulkhead repair

[Zeke69]

Just purchased a 1978 Islander 28 that is in fantastic shape and one of the selling points was that the owner before last replaced the standing and running rigging in 2012. After a thorough inspection I found that all the chainplates were in great shape except the starboard /aft 2. They are coupled over a plywood bulkhead.
That bulkhead is in good shape with all the tabbing well attached. The only rot is a section that surrounds the top bolts on the chainplate. A section around 3 inches wide and 6-8 inches tall.
My thoughts are rather than replace the entire bulkhead, I'll cut out a puzzle piece section and insert a matching piece of starboard epoxied in place, then glass over the repair before re installing the chainplates. Maybe even add an aluminum extension. Once this is all done I can cover the whole shebang with a new section of mahogany plywood and trim it out to hide everything.
Here is a quick diagram I did with my idea. Does this sound feasible? And does anyone have any other solutions that might work as well without total destruction?
Layne
Here is a pic of the chainplate and a sketch of my idea.

[Paul Annapolis]

Layne....It is impossible to thoroughly inspect a chainplate without pulling and polishing it. Chainplates wear in between the deck where they are not exposed to oyxgen. If work was done just a few years ago, apparently the caulking was inadequate or there had already been a leak and early rot and it was not detected. Why would someone who kept a boat in "fantastic" not check for these things over a four year period after such rigging and hardware work. I does not make sense...but who knows?? The water did not just stay but probably traveled further down--maybe not in a straight line either so check the bottom of the bulkhead and end grain there as well. Your idea may work but I would certainly not use starboard as it has no real strength. You might consider instead of a puzzle piece to modify the chainplate and simply add a glued and bolted piece of marine plywood over a larger section of existing bulkhead and attach the modified plate to that newer wood. Similarly, make a new chainplate that would be much larger and bolt that through the good plywood while using epoxy and/or git-rot to fix the hole. I would try to avoid attaching steel to aluminum as well. Best to check all the caulking and beware when you think a nearly 40 year old boat is in "fantastic shape." Good luck!

[Zeke69]

Believe me. I have no illusions about a 40 year old boat. I should have said great shape, for a 40 year old boat. The last owner was an older gentleman that was obviously not capable of doing this kind of work or keeping up with it. The owner before that is a rigger and had the boat for 10 years and had gone through all the systems at some point. I went through every inch of the boat and most of the problems I expected to find just were not there. The 2 year old survey showed the boat pretty well but I don't trust anything but my own eyes.
My next step is to pull the chainplates and inspect and polish them and replace all the bolts. (I'm a jeweler and one thing I do know is how to look at metal) The other chainplates look good so far and are dry. This was the only one with a seep.
I do like the Idea of doubling the bulkhead with new wood. Easier to keep things looking tidy that way. I have plenty of wood rot epoxy on hand. Glad to know that starboard won't cut it. My original idea was to use G10. That is one material I know has the strength for the task at hand. And also glad you reminded me about mixing aluminum and steel. I have to remind myself that marine systems have to be thought out differently. I'll keep a record of how this goes.
I imagine the solution will reveal itself as we break it down for inspection. I'm lucky to have a marina full of experienced helpers and a Coast Guard inspector in the slip next to me.
This is the beautiful bulkhead that I hate to start whacking on.

[roverhi]

Do the repair you've outlined only use a piece of plywood glued in with epoxy thickened with a structural filler like West 104. Sand off all the varnish or finish on the backside and glue on a plywood scab that overlaps your plug repair by at least 3" or more. You could overlap the whole length of the chain plate for the strongest repair. The plywood scab epoxied to the existing bulkhead will be as strong or stronger than the original. Starboard will not bond to epoxy or anything so adds no strength other than the mechanical notches.

[Zeke69]

Thanks for the advice. I think I was making what is really a straightforward job too complicated. Given that all of the tabbing from the bulkhead to the hull is still in perfect shape, fresh wood Epoxied in place should be as strong as the original since we are talking about a 8"x4" section. I'll be breaking it down this weekend and hopefully I don't find any surprises.

[Viedeau]

Absolutely agree. Never use starboard for anything structural or requiring adhesion. It is the weakest plastic you can find - milk jugs - get soft on a warm day

[roverhi]

Epoxying the fill piece in place will hold it but you still should scab a piece on the back to carry the sheer load into the surrounding plywood. If you don't, the sheer load will be only on the notches into the surrounding wood. With a scab you wouldn't need the aluminum strap.

[capndd]

Originally Posted by Zeke69

Thanks for the advice. I think I was making what is really a straightforward job too complicated. Given that all of the tabbing from the bulkhead to the hull is still in perfect shape, fresh wood Epoxied in place should be as strong as the original since we are talking about a 8"x4" section. I'll be breaking it down this weekend and hopefully I don't find any surprises.

Hi,

I have the same issue on the 1973 Sabre 28 I just bought. I was thinking of fixing it the same was as you suggested. How did your project turn out?

Dan

[deltaten]

Use a dovetail shape instead of the puzzle piece. More bearing surface, no shearing effect and much easier to cut.
HTH