Interesting read.

www.sailrepair.co.uk/makingsail.php

That is very good and I know nothing about making a sail but seems it covers it all - makes it tempting... :)

Really good article. I made quite a few of my own slalom sails between 1990 and 2000. They mostly worked fairly well and better if they were just a slight variation on a previous one. The radical ones didn't turn out so good. I made a few 8x4 trestle tables and then when I built my shed I put a pit in it. I've moved since then and don't have the technology or the time. But it was great fun and super economical.