quote:
Originally posted by apache:
Actually, sailboats do not sail with the wind pushing the sail. They operate by the wind passing over the sail, like air passing over a wing. In otherwords, sails are nothing more than airfoils.
Aye, you're correct - when the ship is reaching or tacking. But straight downwind most sails (except the spinnaker - the big baloon-looking sail) are basically something for the wind to push against.
quote:
Originally posted by apache:
Water resistance really has nothing to do with it.
Water resistance is what keeps the ship moving in the direction it's pointed. Ships are shaped the way they are so that they move easily straight forward, but don't move laterally without a lot of effort. A flat raft with a sail will basically go straight downwind, no matter its heading. A rudder can help a bit, but you really need a keel or at least a centerboard to have any control.
The reason a sailboat leans over to the side is that the force from the wind over the sails is usually not in the direction the ship is heading - it's at an angle. Break the vector up into parallel and perpendicular components - the parallel component is what drives the ship forward, and the perpendicular component is what makes it tip to the side.
quote:
Originally posted by apache:
In fact, a sailboat makes the best speed when the wind is blowing perpendicular to the direction of travel. The only direction a sailboat can't travel is directly into the wind.
More or less. Some sailboats (like Hobie catamarans) actually do better on a close reach (sailing at an angle *into* the wind), while a spinnaker will give any ship a big boost downwind.