The fillets on the rudder had cured and I was keen to add fibreglass to the blade and bottom board, so I finished the fillets ready for 'glass.
As usual the finish on the fillets was like rough concrete, so I dressed it with a carbide burr in the corded drill to get it into better shape. As here.
Then I used a flexible, medium-soft pad in the sander to smooth the fillets, like this.
I taped the fillets to be 1 1/2" wide on each face and applied a second layer of fillet mixture to obtain a smoother finish, as here.
When cured this was again sanded with the sanding machine, and a final fairing layer applied to fill the remaining imperfections.
Here is the final layer curing in the workshop.
When cured this will be sanded by hand to a perfectly smooth finish, ready for fibreglass cloth.