How can a sailboat sail into the wind?

Question

I know it's called tacking, but I just can't see how it works!

Answer 1

The magic of sailing into the wind comes from two interesting forces acting together: The wind pushes on a sail, placed diagonally into the wind. This forces it to move backwards and to the side, since the sail is turned diagonally. The sail is steerable independent of the boat, on the mast, allowing the sailor to control (within limits) how much force goes in any direction. The sail is also a curved shape, which will act as a wing (standing on end) when in the wind. This can create a lifting force, just as an airplane wing, which will cause the boat to move not quite downwind as a parachute does.

This sideward movement of the boat then interacts with the water around the boat. The boat's keel acts as another sail - of sorts - to direct the boat forward. This is because the boat is being pushed, and the keel and rudder are positioned to push the boat slightly upwind along a diagonal path.

The entire force of the wind cannot be converted into pushing the boat upwind, but with an accomplished sailor, quite a bit of movement can be developed. This is especially true when a boat can tack quickly after gaining momentum and the sail(s) can be re-adjusted to head diagonally into the wind again - using the other side of the sail.

Answer 2

A sail is an airfoil just like a wing. In fact there are sails that are solid instead of cloth. You generally think of a sail like a jib that fills with wind. Well the sails used for tacking are the ones that are shaped like wings, generally the main sails. From there it is a matter of maintaining the proper angle of attack on the sail.

Answer 3

It works by adjusting the relative angle of sails and boat that way for wind reflection to push sails against boat sideways in angle less than 90 degrees between the normal to sail and the heading of the boat. Thus giving some differential momentum towards the wind. It's better to draw a picture than to try describing it in words, sorry.

Answer 4

Because a sailboat gets "lift" from the keel/centerboard and sails in terms of them being foils, just like an airplanes wing. Hence race boats with tall rigs and deep keels can sail "closer" to the wind than other boats. I'm afraid the physics are beyond me, I just sail 'em.

Answer 5

To put it very simply its high pressure running over one side of the sail creating low pressure on the other side on the same sail. When you have two sails up, the forward one (Jib) will help create the same pressures on the aft (main) one giving you lift. This can only occur when the sails are set correctly, too close to the wind and the airflow needed for the lift will cause the sails to Luff.