We wore a spot on the front edge of the dodger on our passage from the USA down to the Caribbean. Our first attempt at a boom brake did this. It has since turned into a small tear. I knew I would need to repair it soon or it would become bigger and compromise the dodger. However, it was on the leading edge near the bend and under tight tension. In hind sight, there should have been chafe guard there from the beginning.
I wasn't sure how I was going to do the repair due to location. Heather on sv Asseance - a 1992 Caliber 40 (for sale btw) told me she saw how professional canvas guy Sean does it here in Trinidad. He put whatever piece needs repairing in place and then makes the pattern in place, using chalk marks as a placement guide. This allows for bends and shapes. Makes sense.
I bought a plastic drop cloth specifically for making canvas patterns. However, this was a small pattern. Instead I was able to use two sheets of tracing paper taped together. From that I cut a muslin pattern to further test. Before last season I found the perfect chafe guard fabric at Radica Trading here in Trinidad. It's a marine vinyl with a slight texture. Turns out it matches other chafe guard fabric on the back edge of the dodger.
First I sewed a tiny patch of Sunbrella over the hole to help stabilize it and keep it from spreading further. Next I sewed the front edge of the chafe guard in place. Then we put the dodger on, stretching it tightly into place. Then I chalked the sewing line for the other side. This allowed me to take into effect that the chafe guard fabric needed to come up and over the dodger metal frame - not quite 90 degree but enough to affect where the back edge was sewn. If I had simply sewn it on flat, it would be off when put into place most likely causing fit issues. The dodger is so tight on the frame, there is little room for error.