Originally Posted by MacG

The only way to sail a bike faster than the wind is to have a wide vehicle that can resist a serious tipping power.

A run, when the wind is at your back, allows you to approach the speed of the wind and applies little to no tipping force to the craft.

When the sail is hauled in and the craft turned to cross the wind, then the speed picks up. I think the optimum angle (for a boat) is about 30 degrees off of the wind on either side. The elusive component that allows a sailboar to move forwards and not just blow sideways is the keel or board. The boat has what is literally a wing flying through the water underneath it. The propulsion (other than on a run, when you have a floating parachute) is caused by the fighting of the wing under the water against the wing in the air (the sail).

If you had a wide trike, you could probably sail crosswind. The keel's job would be provided by the wheels (preventing the sideways motion of the craft) and as long as the rig was wide enough to be stable, you could probably get some speed up.

The biggest problem is that you are heavily limited by the direction of the wind, so you would probably only be able to sail in a large open area, like the salt flats or a big sports field. I don't think that a sail would be able to provide any advantages or even be very feasable in town or on trails, unfortunately.

That said, I'll put in a six pack to the first person to create a sailbike capable of traveling crosswind at speeds greater than the measured wind (without pedal/motor assistance, naturally). Gentlemen (and ladies); start your welders!