Physics behind sailing?

Question

Could somebody here explain how a sailboat could sail against the wind? There should be physics behind.

Answer 1

Kevin has it mostly right, Runni is in the running.....as was said you cant sail right at the wind but only about 40 degrees each side, ziggzagging upwind or beating up wind....if you've ever done it for four days you'll know why it's beating.....and yes a sail is shaped like a planes wing creating suction on the lee side of the sail that makes the boat want to go forward......
and here's my contribution...sailboats have keels or centerboards that stick down into the water and prevent the boat from slipping sideways; so since the boat cant go sideways the force on the sail pushes it ahead..

Answer 2

There are about 30 degrees on each side of the direction of the wind where a sailboat will not sail. It's called the "NO SAIL ZONE". The boat will literally stop, it's impossible to perpindicularly sail against the wind and 30 degrees to each side of the perpindicular. Basically the wind cuts right through the sails.

You can sail "against" the wind in a close-hauled or close reach sail point. Here you're not perpindicularly attacking the wind head on-, but you're "catching" the wind in your sails as close as you can to the wind direction.

I'm not a physics guy.. but If Wind was a Vector.. and that Vector acted upon an object (sail boat) in any way.. the boat speed and subsequent direction would be directly proportional to angle of attack, and the built up energy (kinetic?) in the sails would propel the sailboat...

Something like that... Sailing is basically "catching" or deflecting the wind in such a way that the deflection or "energy capture" translates into movement.

Answer 3

The more primitive sailing ships using square sails could only be pushed by the wind and could not sail against it. However, more modern sails are shaped so as to create an airfoil much like the wing of an airplane. The airflow around an airfoil creates a pressure difference that pushes the ship in the direction of the lowered pressure. Such ships still cannot sail directly into the wind, but can sail towards the wind at an angle using a zigzag motion known as tacking.

This is a rather sloppy answer, as I am not an expert in sailing, but simply familiar with it through my physics background. A better answer is available here:

http://en.wikipedia.org/wiki/Sailing

Answer 4

If the boat is sailing directly against the wind with sail up, then the wind will slow the boat down. But if the wind is not acting in directly the opposite direction to motion, then a certain component of the wind will help the boat move.
Also wind causes waves which push the boat