The parts for the mainmast box, the sides are 9mm plywood. Once assembled this area will be very difficult to access for repainting so I"m making a good job of the coating. Three coats of epoxy, and that will be sanded and painted with two part polyurethane paving paint which is very resistant to both abrasion and UV so should last well.
Another little job to do. I'll be building a battery box in here, it needs to be such that the weight of the battery will be carried by the bulkheads rather than the bottom panels as bumping along the road on the trailer with that weight sitting on 9mm plywood wouldn't be good.