Sailing Using Water and Wind

On a calm and clear day, the water and wind will be moving in the same direction. This is not the most ideal situation for any sailor as there is not a good amount of energy to extract for movement. There is a capture of energy from the wind and water that is created by the diference in motion. The sailboat captures this energy by utilizing the sail(s) and the hull(s).

There are usually two different directions, the sailboat and the wind, and both of these create a relative or apparent wind. A sail uses this apparent wind and generates lift. This is an example of an airfoil, and using Bernoulli's Principle the airfoil creates lift much like an airplane does. In fact, depending on the orientation of the sailboat, its point of sail, and its design it could conceivably obtain a speed faster than the true windspeed.

The sail aids the boat in movement in the water. A boat in the water must not only be able to move, but be able to change directions. To help direct the boat an underwater component is required, such as a centerboard, underwater foil, keel, or even the hull itself can be employed. Movement can be acheived in any direction except directly into the wind with the sail and underwater component.

The boat's movement relative to the true wind ranges from 35 degrees to 80 degrees and is called the tacking angle. Using a 35 degree tacking angle, on either side of the wind, a sailboat could cover over 290 degrees of the boat compass. Sailing into the wind can be accomplished indirectly by sailing close-hauled, about 45 degrees, and then tacking and sailing in a zigzag fashion. There is a relationship built between the sail and underwater component to move the boat in a specific direction.

Understanding the dynamics between capturing and using the energy from the motions of wind and water can help answer the following questions:

1)How do sailboats move?

2)How can a sailboat sail upwind?

3) How will a boat sail faster than the wind?

Most sailors are not physicists but they are undoubtedly cognizant of the physical principles that govern basic movements in the water when sailing. These principles allow the boat and its crew to move in the water.