Fixing a hole on a wooden Albacore

Hello! I have a 1968 wooden albacore which I am restoring this winter to keep sailing. Removing rotten wood I now have a hole (5 cm x 10 cm) in the bottom of the hull which I need to fix.

If I use the 8:1 rule that would make the repair huge. Any recommendations on how to patch it?

Do you know what wood are those boats made of? Looks like some kind of plywood or some overlapped p thin planks.

Thank you!

If scarfing the repair into the hull would make the repair too big, perhaps you can simply fill in the hole neatly and put a big backing block - similar to a butt block used in carvel planking - on the inside. Do note that the scarfing ratio is based on the thickness of the plank you’re scarfing in to. If the hull is 1/2" thick, the scarf would extend out 4" from the edge of the hole if you’re working with an 8:1 ratio. Do note that, according to Google:“Traditionally, scarf ratios have been driven by the location of the scarf: 4:1 for planks, 6:1 (possibly 8:1) for keels, and 12:1 for spars.” If you make the repair with epoxy instead of wood, the ratios may be different.

Thanks. I though of the backing block but want to keep it nice inside and out. As I will have a stringer running over it it will also give it strength. The boat is a 3 ply construction. Not sure what the wood is. I’m wondering if I can put a single piece or if my patch needs to be three ply as well…

That looks ragged enough to make it difficult to repair in wood. You’d have to make the hole bigger just to square it off. It already appears like it’s got a bevel on three sides. Filling it in with a fiberglass/epoxy repair would be quicker & easier than wood. Maybe with a waxed piece of plywood on the inside to create a mould & support it until it kicks. A layer or two of 'glass cloth/epoxy, then some epoxygoop with chopped fibers for strength, then another layer or two of 'glass cloth/epoxy to tie it in with the outside of the hole. Sand it smooth on the outside and you’re ready to paint.