Sailing

I

Introduction

Sailing, propulsion of a boat or ship by means of the driving force of the wind through the use of sails. In sailing, noncommercial boats are used for pleasure, especially for cruising, racing, or fishing. The pastime involves the use of a sailboat, which may be a small boat powered only by wind or a larger vessel that can also be propelled by an inboard or outboard motor. Some sailboats have living quarters that allow sailors to spend long periods of time on the water.

II

Basic Principles of Sailing Boats

Methods of sailing vary according to the manner in which boats are rigged, but the essential principles of sailing are the same for all craft. The simplest and most easily understood point of sailing is called in nautical terms sailing before the wind. The term running before the wind is also used. As the term indicates, the boat follows the same course that the wind is blowing. As shown in the first diagram in Figure 1, the sail or sails are set at approximately a 90° angle to the longitudinal axis of the boat, with power derived from the push of the wind on the sails’ back surfaces.

In sailing off the wind, as shown in the middle diagram, the wind reaches the craft from the side, or beam, and the sails are set at approximately 45° from the axis of the craft. In this sailing position, the wind exerts a pulling rather than a pushing action on the sails, which act as airfoils, like the wings of an airplane. The general principle of wind action is that the wind flows at a greater rate of speed along the forward surface of the sail, creating an area of lower pressure ahead of the sail. The actual force exerted by the wind is at right angles to the sail, as indicated by the dotted line a. This force would tend to drive the boat at an oblique angle if the hull of the boat were perfectly flat. Every sailboat, however, is equipped with a fixed keel or a retractable centerboard, which acts as a flat longitudinal plane to prevent the boat from moving sideways through the water. The effect of this plane is shown by the dotted line b, and the actual course of the boat, the result of both the force of the wind and the resisting force of the keel, is the dotted line c, representing forward motion.

III

Tacking

If boats were able to sail only before the wind and off the wind, it would be impossible to reach a destination upwind from the starting point. By sailing on the wind, however, a sailboat can make a course approximately 45° away from the wind direction, as shown in the diagram in Figure 1. By sailing a succession of such courses, first to the left and then to the right of the wind direction, a maneuver called tacking, sailboats can zigzag in an upwind direction, as shown in Figure 2. A vessel is said to be on the starboard tack when sailing so that the wind is blowing from the right or starboard side, and to be on the port tack when the wind is blowing from the left or port side.

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The procedure of shifting a vessel from one tack to the other, called coming about, may be accomplished in either of two ways. The boat may be steered so that its bow (the front end) points up into the wind and then away from the wind on the opposite tack. As the boat points into the wind, it loses speed, the sails being pressed directly backward by the wind. Then as the bow moves away from the wind on the other tack, the sails fill with wind again and assume a position on the other side of the vessel. During the time of coming about, the boat is receiving no motive force from the wind; it must rely on its momentum to maintain enough speed so that it can be steered onto the opposite tack. When the boat does not have sufficient momentum and stops with its bow pointing into the wind and its sails useless, it is said to be in irons.

The other method of changing tack consists of steering the boat away from the direction of the wind, until the wind fills the sails from the other side and the boat is on the other tack. In fore-and-aft-rigged vessels, this maneuver is called jibing or gybing, and in square-rigged ships it is known as wearing. When running before the wind, a slight shift of wind may cause a boat to jibe unintentionally. Such jibing is dangerous because of the speed with which the heavy booms, or spars, at the foot of the sails sweep across the decks of the vessel from one side to the other, and also because of the danger of breaking spars. In wild jibing, control can be lost momentarily and, if the seas are high, a small boat can broach—that is, veer on its side with danger of swamping or capsizing. An unintentional jibe in a heavy wind frequently has enough force to break the masts of a vessel. When jibing intentionally, careful sailors always haul in on the boom while turning, so that the boom will travel only a short distance when the wind reaches the other side of the sails.

IV

Reefing

During stormy weather, the area of sail exposed can be reduced by another procedure of sail control known as reefing. Reefing is accomplished by bunching up a portion of the slackened sail along the yard or the boom and then securing the folded canvas with small ropes called reef points. The part of the sail thus taken in is called the reef.

On all sailing ships, sails are hauled up and, to some degree, controlled in accordance with wind direction by ropes called sheets and halyards. For the most important of these ropes, as well as other portions of the fittings and rigging of sailing ships, see Sail.

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