Today the mast was unstepped and the boat was hauled out. I removed the mast step and found the area beneath it had been slightly compressed. I sounded it with a chisel handle and it was immediately obvious that there was a void under this area. I figured this was due to plywood core that had gotten wet and rotted. So I decided to replace the core with G10. I cut a small square to start that would be hidden by the mast plate. The square popped off easily, revealing…an aluminum plate embedded underneath!
The compression I had observed was due to a void in the fiberglass between the top skin and the aluminum plate, which can be seen in the photo below. So the fix will be to reinstall the top skin with thickened epoxy, glass the seams and then paint. The whole repair should be mostly hidden under the mast plate.
I’ll also add the support described in a previous post to the compression post.

The compression I had observed was due to a void in the fiberglass between the top skin and the aluminum plate, which can be seen in the photo below. So the fix will be to reinstall the top skin with thickened epoxy, glass the seams and then paint. The whole repair should be mostly hidden under the mast plate.
I’ll also add the support described in a previous post to the compression post.
