How Can a Sailboat Travel in a Direction Different From the Wind?

Since Nathaniel Bowditch first wrote "The American Practical Navigator" early in the 1800's, millions of people have taken to the sea on sailboats. Powered by the wind, sails are shaped to catch (or release) what wind is available, and use it to drive the boat forward to its destination.

  1. Wind Basics

    • Wind is invisible, but its power is measurable, noticeable and usable. Wind is created when there is a pressure difference in air masses. For sailing, both vessel speed and wind speed are measured in knots rather than statue miles per hour. According to the Beaufort Scale, wind can first be felt when it is blowing 4 knots

      True wind is that which is naturally occurring. Apparent wind is the combination of true wind with the wind created as a boat moves forward.

      Wind direction is that from which the wind originates. If a boat is sailing toward the northwest, with the wind coming from the northwest, it is traveling against the wind, and must zig-zag to progress.

    Sail Basics

    • The most common vessel for recreational sailing is the sloop, a single-hulled vessel with a single mast, and two triangular shaped sails: the main sail and jib. Sails are made to function by pulling lines that control the corners-head, clew, tack-and edges-luff, leech and foot.

    Points of Sail

    • Points of sail are not actual compass directions, but indicate what part of the boat the wind is moving across. "In irons" is the condition with the wind head on. It is the only point at which a boat cannot actually move.

      Close hauled is sailing as close to the wind as possible. A close reach is between close hauled and a beam reach. The beam reach is sailing with the wind 90 degrees to the boat. Broad reach is the point with the wind between the beam and stern of the boat. Running is sailing with the wind directly behind the boat.

    Sailing

    • The force of wind upon a sail creates "lift," which pulls it forward. Forces that oppose the boat, such as currents pushing against the hull, create "drag." Shaping the sail to catch the wind requires adjustments to find the ideal balance between lift and drag.

      By adjusting the sails, any boat can move very close to, or away from the wind. The actual functions are called "easing," or letting out, and "trimming," or pulling in the sails.

      A sailing course is highly recommended for anyone with dreams of owning or operating a sailboat.

    Measurement Devices

    • A barometer indicates pressure changes.

      Modern day boat owners can find a wide array of instruments and devices to keep them safely informed while on the water. A solid list of instruments awaits the savvy sailor heading into ocean waters, but the basic instruments common to sailing include an anemometer for measuring wind speed, a wind vane to measure wind direction, a compass to indicate magnetic direction and a barometer for measuring pressure changes that result in wind. Wind is the controlling factor for all sailing.