If 30 feet is as tall as I think it is (10m), then i think you should give your fixed wing sail some more thought. I'm sure that then you would see it isn't such a good idea.
Interesting? Yes... What board are you going to put under it? And how are you going to control it? :|
No offense but are you sure that you aren't being suicidal here??
If you are really into such big ''sails'', why not get a sailing boat?