In preparation for spar sanding, I decided to cut the openings for the mast sheaves. I pulled the Delrin sheaves from a pair of old Schaefer blocks I found in the shed (don’t know what boat they came from). Both are approximately 3/16″ short of the mast tips and will work just fine for the halyards.
I jigged the spars level on the open bench, chocked them in place, and bore holes for the sheave slots. A Forstner bit did quick work of it.
A chisel and utility knife roughed the edges to shape. Filing completed the needed slot width.