Sail design seems to me such a dark art that to try and find good written articles on how to design sails are few and far between, in particular most articles are written about slow speed dinghy sails which are not much use to A cats where the wind is almost constantly apparent wind. Does anybody know of any good websites / books etc that fill in a few gaps for me. My long term intention is start to build a few sails for no other reason than to try and understand them more.