Originally Posted by AlanK
I thought I'd go ahead and revive this thread since it's an interesting topic. Sounds like my thinking is pretty similar - I was thinking about the idea. It also occured to me that a recumbent would be more well suited for a sail because of the lower center of gravity.
That said, as others have mentioned a small, adjustable, removable sail on a standard bike might be useful in some situations. If you were traveling with a tailwind or light sidewind, it could provide a useful boost. This is especially true with hills: if you're riding a long, steady incline with a tailwind, it seems to me that a sail would make climbing much easier. Since you would be going that fast, there'd be a little to no drag effect.
Obviously there are conditions where a sail would be a hindrance: When you are riding on flat or downcline surface with little or no wind a sail would obviously create a great deal of resistance (which it why it would need to be easily removable). An obviously it's probably not a good idea in the city, only on an open road (even then it would need to be fairly small). But I'm really curious if anyone has had any progress and success with this idea.
I discussed the possibility of a recumbent sailbike a few years ago with Tom Traylor. He pointed out that it would be very hard to shift your weight quickly enough on a recumbent to accomodate the wind gusts. So as far as a bike, I'm inclined to agree with Tom that an upright sailbike would be easier to control than a recumbent. However, with regard to a trike or a quad, I'm inclined to think the lower recumbent cg would be benefit on a cycle having a wider track.
In the DC area where I live, there are many bike trails. I'm looking at systems having sails that would remain within the 36 inch width of my recumbent trike.