Repair Tips: Backer Plates & Mounting Cleats

By Jerry Cronan

Putting a backer plate in an inaccessible area

Here is how I fixed an unwanted hole in the transom of a foam-filled boat.

1. I drilled a ½” diameter hole on each side of the unwanted hole,then used a saber saw to connect the holes to form a slot.
2. Next, I cut 4mm thick plywood into a football-shaped backer plat that would fit through the slot the narrow way. I attached strings to the plate, coated it with epoxy then slipped it through the slot.
3. Using the strings, I turned the plate so that it covered the three holes and the slot. Reference marks on the plate helped me get it in the right position.

Mounting a cleat

This same basic method worked well for mounting a much needed cleat on a balsa cored deck. There was no access to the back, so it was a seemingly impossible operation. Here’s how I did it:

1. I used the cleat as a template to bore and tap an aluminum back-up plate. Then I used the plate to mark oversized holes in the deck.
2. I drilled the screw holes and cut a slot in the deck, centered between the holes holes. This slot passed all the way through the balsa core deck and lower laminate.
3. I used a small wire to fish a string diagonally through two of the holes in the plate and the matching holes in the deck.
4. I coated the plate with epoxy, pushed it through the slot and used the string to finesse it into position under the deck.
5. I used a syringe to coat the top of the plate and fill the slot with thickened epoxy. Then I coated the bottom of the cleat and mounted it in position over the holes. I threaded the screws through the cleat and deck into the two plate holes without strings.
6. Before tightening the screws, I pulled the string out, then put the remaining screws in the holes where the string had been.