Cracking within centerboard trunk

[Luke]

I have a 1975 Daysailer II that has cracking within the centerboard trunk, about an inch up from the bottom of the hull. It's parallel to the slot on both sides and does not appear to be separated or displaced more than marginally. It's on both sides of the forward and aft ends of the slot, extending about 18" that I can see from each end. The slot is about 54" long, so 18" from each end (36" total) is most of the slot. The cracking may be more extensive but with the centerboard in there I can't see all of it. I've read some postings on similar issues though I'm uncertain if I captured all of the exchanges about this. From what I was able to find, the fix might be West Epoxy Repair with both fiberglass fabric and epoxy, which would involve taking down the gelcoat and laying in the fabric and epoxy, then fairing and finishing off with gelcoat. I have some minimal experience with fiberglass repair. I'm willing to give it a try though if I knew of a fiberglass repair shop familiar with this, I would also consider that. The one local shop I visited was unfamiliar with this and thought that the repair would be very expensive. I'm hoping that only the gelcoat is involved. I plan to get a borescope so I can see the other side in the bilge to evaluate if more than a bottom side repair would be needed. I'm hoping to address this with just the bottom side repair. That has its own complications, one of which is getting some sort of tool into the slot (after centerboard removal) to take down the gelcoat. It's pretty narrow. One person suggested a Dremel tool. I would plan to slide the boat off the trailer enough to access the centerboard, with structure to support the boat, and do the work from below. The boat is taking on water in the bilge, maybe a gallon an hour or less, and it's uncertain if the cracking is the source of this. I'm viewing this as structural and therefore necessary to repair, and I would address potential leaking at the centerboard pivot bolt and at the uphaul line exit point in the course of the repair. Is there a good way to make sure I picked up all of the threads on this? Does anyone have additional information on the topic or experience with the repair? I would appreciate any comments on repair processes, tools, materials or repair shop in the Pacific Northwest (Eugene Oregon or nearby). I'm attaching photos.

[GreenLake]

I don't know what you did to your boat, but I'm afraid you are correct: this looks structural, not cosmetic.

A tool you might consider for removing the gelcoat and damaged laminate around the crack is an electric file. Those are essentially really narrow belt sanders. Since your crack is pretty close to the opening of the trunk, you should be able to get the tip of one of those in there. It may take a bit of trial and error, but you should be able to grind a shallow V where the crack is now.

And I would take the gelcoat off for about 1-2" beyond the crack.

Then you need to prepare the fiberglass to fill the repair. The good news is you can do that on your bench. Lay down a strip of plastic. Then lay down the widest strip of fiberglass you want to use. Followed by those that stair-step to the narrower widths you would place inside the widened crack. You can all wet these out comfortably on your bench in one go. Essentially you'd be creating your own "repair tape".

You'd move it from bench to repair, while still on the strip of plastic. You might want to use some packing foam to hold the "tape" in place until the epoxy sets. Get some nice even pressure on it. (If you use masking tape to seal the edges, not too much epoxy should run out.)

BTW, don't be afraid to add a layer or two two that would be proud of the surface when done. There should be enough room in the trunk and you can probably use the extra strength.

After everything has cured, use the electric file to smooth out any lumps. Don't bother with gelcoat. Just use some waterproof paint. All it needs to do is keep any remnant of UV off the epoxy. Pool paint would work, so would bilge paint, or bottom paint. Deck paint works for boats that are dry sailed with limited duration immersion.

If you've never worked with fiberglass before, or it has been a while, please lay up a test strip on your bench. Just to make sure you get something that cures as expected. Better safe than sorry.

Altogether not a very difficult repair. You might even get motivated to refurbish the leading edge of your CB a bit

[Luke]

Very helpful! Thank you.