Quite interesting sails on the foiling 18foot skiff in Switzerland. Mainsail have a top raked upwards and the spi have a very straight luff. For a boat building a lot of virtual wind and not going too deep, the spi seems like a very good design to me. The mainsail is a somewhat different beast. I dont think they get too much draft in the top with the heavy battens needed to support the top and leech, but drag might be less than with a conventional square top. Probably not something dramatic, but a small incremental gain perhaps. I have not studied the sail measurement rules yet. Would you gain "free" area by doing such a design, or will the measurement rules catch this?



Cool to see "new" developments! Who will do the first F-16 trials <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />