When I installed the mahogany cabin side I very carefully scribed and made the cut-outs to fit the portlights with a little bit of slop vice mirror the existing too large cut outs. So, now there is a bit of a lip that still needs to be addressed. More on that tomorrow.
I clamped the portlights in place with two twist clamps. I then viewed the spigots from the outside making sure they were centered. I used a small bubble level to make sure they were level. I drilled through the portlight frame about 3/16” deep for all the holes. This made sure they were in the right place. I then removed the portlight then used a small home made drill guide to insure I was drilling perpendicular to the cabin side. The guide is a small 90 triangle about 1 ½” long on each side. Once angle is 90 degrees. I placed it on the cabin side and matched up the 90 degree angle to the bit and started drilling. I moved this little triangle around to keep the drill going in straight and plumb all the way through the cabin side. Then I inserted all the bolts to check for fit. It took all day to fit the10 portlights.
The next thing was to over-bore the holes to reduce the likelihood that water can migrate along the bolt threads into the exposed grain of the plywood. So, I drilled out the 3/16” holes for the #10 machine screws with a 5/16” bit. I would have preferred to use a 3/8” but it would put the edge of the hole very close the edge of the cut-out and the 3/8” bit I have just tears through fiberglass in an ugly uncontrolled manner. After drilling the holes I covered the hole on the inside of the boat with tape. Then, I filled a syringe with West Systems epoxy thickened with colloidal silica and carefully filled the holes till they were flush on the outside. I had to refill the syringe about five times. Last, I smoothed the uncovered end with a plastic stir stick and cleaned up any spill over with paper towels wetted with acetone. A few hours later I removed the tape covering the holes on the inside of the boat and the epoxy “plugs” looked good.
Tomorrow, I will drill through the epoxy “plugs” with the 3/16” bit and if I do it right I will have an epoxy sleeve that surround the bolts and keeps any water that get to the bolt from migrating to the wood grain.