Repairing a rotten bulkhead..

[SVDistantStar]

Well its time to start the BIG projects on my Pearson 36 now that shes paid off. #1 on the list is the rotten bulkhead. The main bulkhead that the port chainplate is attached to is rotten all around the chainplate. Its rotted due to the chainplate leaking from the deck. Ive sealed off the leak, but the rot is too bad now. I can't sail the boat untill this is repaired.

Now the hard part is how do i repair this? Pretty much an area around the chainplate going out for 4-6'' in all directions is rotted. The rest of the bulkhead is solid. Ive been thinking i could just cut out the bad section and add in a new piece of wood and fibreglass it to the old bulkhead and hull. Anyone got any other ideas?

My rig is in no danger of falling anytime soon as it is keel stepped and the mast is oversized for the boat. I didn't find the rot until about a year after owning the boat. In that year we took it sailing every weekend and never lost the stick.

The chainplate in question is in the left of the picture. Its the large metal plate. This differs from the normal Pearson 36 setup as its been changed so all the stay line up with each other. All are on one chainplate.



In this picture you can see the 3 stays where they enter the deck.

[sailingdog]

SVDS-

Yes, you can scarf in a new piece and then fiberglass it to the hull and remainder of the bulkhead and if properly done, it should be strong enough to handle the loads of the chainplate. However, IMHO, I think replacing the entire bulkhead makes for a stronger repair, but is a lot more work. It shouldn't be too bad though, since it appears that the port side is completely separate from the starboard side... so you'd actually only be replacing half a bulkhead.

[Jeff_H]

The hardest part of replacing a main bulkhead is getting the plywood into the cabin through the companionway, and getting access to the hull and deck on both sides of the new bulkhead to properly tab in the new bulkhead. Typically getting the plywood below decks means that you end up building the bulkhead out of multiple pieces of plywood that are less than 2- 2 1/2 feet wide depending on the width of the companionway, and laminating the bulkhead out of plywood that is half the thickness of the bulkhead so that you can stagger the joints. The repair technique really depends on your goals for the repair and your skills.

Jeff

[hellosailor]

Not being a structural engineer but having had some real-world experience with breaking things...

I don't think I'd trust a scarfed-in repair. Sure, you could cut out an oval of new wood or fiberglass board that was a foot or so across (no corners, fewer stress concentrations) and then just replace the area where the chainplate bolts in. But all the stress is now being put on the edge of the join, which is what? 3/4" or inch thick bulkhead? Given some lateral movement forward or aft, I'm not sure how well that would hold.
If I did it that way, I think I'd want to sister up overlapping larger plates, with a good 6" overlap, on both sides of the bulkhead. Wood, fiberglass board, or bronze or stainless plate, any one of them, just to ensure that the "plug" couldn't pop out of the bulkhead. All through-bolted together as well as epoxied.

The alternative is replacing the whole bulkhead, which structurally and aesthetically is probably the only right way to go. But a lot of work, chewing out the old bulkhead, slicing clear whatver they've joined to it "forever", replacing that all again. Some of those nice Japanese hand saws, a bit of molding...and maybe a week or two working with your best friend?

Congratulations on the paid off! And just what IS the boater's equivalent of a mortgage burning ceremony anyway?!

[feetup]

I agree with Jeff, that if the majority of the bulkhead is sound you can, in theory at least make a repair that is every bit as strong as the original by scarfing in a section of bulkhead.
Keep the thought though, that if you were to suffer a hard knockdown the momentary loadings on the chain-plates could easily be equal to half the breaking strength of the three wires that are trying to pull it through the deck.
The ideal repair would be the whole bulkhead, but if you replace just the outboard section, and ensure a well fit scarf joint to the existing bulkhead and plenty of carefully applied tabbing to the hull you should be fine. Careful workmanship is the key.
Personally I would not trust a horizontal joint, at right angles to the line of force. I would be comfortable only with a vertical scarf joint or perhaps a well fit half lap since glues function poorly in a tensile or straight pull application but very well in sheer, or trying to slide one part past its mate.
As Hellosailor pointed out, you can gain insurance by sistering up a panel on the other side of the bulkhead and through bolting the works. Both sides would be better, but I see you don't have room aft.

Feetup