What Sailrite resource is the best for designing and creating a gaff sail?
The best option is to have Sailrite make up a custom sail kit for you. The cost of design and panel cutting is negligible and having precut panels and patches makes assembly very easy. Just answer a few basic questions about your desired sail at the Sailrite website to get started.
If you prefer to build your sail the old-fashioned way (lofting on the floor), we suggest the Mainsail Manual Book or The Sailmaker’s Apprentice. Both books are full of good information on sailmaking.