Cut hole in fuselage skin for fans using hole saw. As the teeth of the saw were much too aggressive for the aluminum skin, I used the hole saw turning backwards. The hole was slightly undersize so I enlarged it using a drum sander and deburring tool.
Once the hole was the correct size, debur and smooth all edges using s/b wheel.
Cleco doubler in place, verify fit of fan grille.
Match drill the fuselage skin to the fan grille.
Remove doublers.
Debur holes.
Dimple all holes for flush rivets and screws in skin and doublers.
Cleco doublers in place and rivet using p-squeezer.