Porthole Installation.

 I decided to decorate the outside and inside surrounds of the porthole windows using 9mm thick plywood rings.

I made the rings large enough to overlap the 6mm marine acrylic portholes. The outside rings will be permanently epoxied in place and the portholes will be sealed and screwed in place with marine bedding compound from the inside. The inside rings will be screwed over the acrylic porthole window (This will allow future replacement if required). 

This pic shows the 6mm marine acrylic porthole with protective covering alongside the drawing of the decorative ring. 

Using a jigsaw, I cut out the rings and cleaned up with a bench sander and a circular drum sander. 

Here are the eight decorative porthole rings ready for edge routing.