I did this last Monday 8/20/17, but didn’t get to post until today.
I did this exactly to instructions, but after I wished I had deviated a little and used my laser cutter.
From 1/4″ aircraft grade poplar plywood, I cut 20 1″ circles using a hole saw. I trimmed the flashing with a knife and sanded the loose bits off the sides and face. I did not sand them smooth.
2×4′ was the smallest I could order from Aircraft Spruce. Looks like I could have fit them all the way across and saved material if I’d thought of it sooner.
20 rough cut circles.
After trimming and sanding. Rough edges will help epoxy grip. All the loose material or over-sized bits are removed and they should fit nicely in the spar holes.
Before and after trimming and sanding. It took a long time to do them all. Next time I’ll just laser cut them a little larger and sand off the heat affected zone. Less mess and I’ll have a nicer finished product.