I tested the new yak 'trimaran' this week in about 25km/h winds in the local gulf off Brighton. I got a maximum speed of about 9km/h while still trolling. I wasn't after the top speed, I just wanted to test to see how it handled for trolling. It was close to perfect! (Unfortunately the fish weren't cooperating though) But I still have an urge to get the most out of her as a sailing trimaran, so the issue of a better sail is still in my mind.
I have been looking and thinking about a better wing sail design that can be furled either partly or completely. I have thought of a couple of ideas, but I think I might have come across a very simple and easy solution.
It's a gaff sail with a full length 'luff pocket' that fills with air when the wind flows over it. It is a 'self inflating' pocked that maintains an airfoil shape without any need for a filling to maintain the shape. I have seen discussions about this kind of sail but not seen anything with as much detail as to construction.
I want to make a bigger sail now that I have a more seaworthy rig, so I think I will be making this one!