I picked up a nice sturdy 11k RPM grinder this morning. With a 100G flap disc, it made short work of removing the rest of the material from the starboard window I’ve been working on (slowly but surely) for two weeks. I almost immediately realized a variable speed grinder would be nice though, as it’s hard to control the grinder at 11k RPM for any kind of fine work. But I guess that’s what my orbital sander is for anyway.
The work of fairing the old window cutout has been pretty painstaking. The grinder will make things much faster with the remaining three windows, but it’s still a lengthy epoxy, grind, epoxy, grind, epoxy, grind, sand kind of cycle that requires a lot of patience to get something that looks fairly nice. The inside rounded corners of the opening are hardest, since they’re too tight to really grind smooth. In the end I’ll settle for “close enough” as I’m sure nobody will ever notice any of the small imperfections anyway.
I test drilled a scrap piece of polycarbonate with a 6.5mm HSS bit (to fit M6 bolts). You have to be careful about overheating, but aside from that, a little masking tape on each side of the glass seems to prevent any chipping from happening. They do make special bits just for plastic, but I’ll leave finding one of those in Singapore as an exercise for someone else.
With some luck maybe I’ll have the two front windows both finished by the end of next week.