Using Wind and Water While Sailing

It is an absolutely clear and calm day, and the wind and water are moving in the same direction. There is not an ideal amount of energy in this situation, to extract for movement. The wind and water together create a difference in motion, which is then captured by the boat in energy. The sailboat captures this energy by utilizing the sail(s) and the hull(s).

The difference in direction between the sailboat and the wind is the 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.

Using the sail, the boat will be able to move in the water. If a direction can be chosen, it is better than if the boat can move in the water alone directionless. 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. The boat can move in any direction, except into the wind, with the underwater component and sail.

The tacking angle, the angle of the boat’s movement relative to the true wind, usually ranges between 35 and 80 degrees. 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. An underwater component and sail work together and move the boat in a given 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 does 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. The crew of a boat would be stuck in the water, if it wasn't for these principles.