Sanding the fillet under the cockpit coaming of my Wood Duck 10

What is the purpose of sanding the fillet under the cockpit coaming? Is it to smooth it out? Is it to make sure the epoxy will stick to it? I did apply the fillet and it has been over 24 hours so it is now fully cured and I believe the next step is to sand it, but I am not sure how much sanding to do. Just to smooth the sharp edges or do I sand it all, even the already smooth areas? Thank you very much for your advice. Diane

It’s to make it smooth. A smooth fillet does a better job of eliminating stress concentrations. It also doesn’t snag any glass cloth that may come into contact with it.

Dowels or pencil-sized sticks of foam can be wrapped in sandpaper to make sanding tools that fit under the coaming.

Laszlo