I've been repairing my own canvas for years on three of our past boats, starting back in '85 by restitching a full-camper canvas, replacing isenglass and zippers. The project came out surprisingly well for my first boat-canvas attempt.
Essentially, the old panels were used as a template and I simply followed the stitching patterns of the original. It was fairly straight forward work, with a shallow learning curve for me. Initially, only a couple of short runs went off course a bit. This was corrected by pulling the bad stitches and resewing.
I did have some upholstering experience a few years before, during a project I designed and built for us involving entire sets of living/dining room furniture, still have the sofa/chair and end table in the family room. I cut and stitched all cushion covers - after doing much reading on the subject. We still get comments on how well-made the set is.
I did not purchase a Sailrite, or commercial grade machine dedicated for heavy duty sewing. Instead, used a '60s era all metal, Singer sewing machine - a family hand-down. Amazingly heavy duty machine, but still limited to 4-5 layers of canvas weight material.
It was used for a custom sun awning I designed and fabricated for the last boat, which came out very well. We saved a ton of money through the years by doing all the work myself. I would say though, a certain amount of talent is necessary - especially with layout, design and eye/hand craftsman skills.
True Blue . . .
sold the Nauticat