On Yacht Sailing / A Simple Treatise for Beginners upon the Art of Handling Small Yachts and Boats

by Thomas Fleming Day

DIAGRAM B.—BEATING OR SAILING TO WINDWARD. BOAT, DOTTED LINES, IS ON STARBOARD TACK; BOAT, FILLED LINES, IS ON PORT TACK.

SAILING ON THE WIND

Sailing on the wind, or by the wind, or close-hauled, is a purely mechanical action, the motion being the result of opposing two forces, the wind pressure and the water pressure. The wind pressing on the canvas forces the boat sideways, her form causes the water to resist this movement, and as it is easier for her to progress in the direction of her length she moves that way. Her sails being arranged so as to transfer this movement in the direction of the bow, she moves ahead. It is to prevent her going sideways that a boat is given a keel or centerboard.

In sailing to windward a boat’s sails are trimmed flat—that is, the sheet is hauled in until the foot of the sail lies nearly parallel to the line of the keel. How close to being parallel depends largely upon the form of the hull, an easily driven model being able to sail with a flatter sheet than one of coarser dimensions. No rule can be laid down for trimming the sheets of a boat when sailing on the wind, it depending upon the form of the vessel, the strength of the wind, and the condition of the water.

As the movement of the boat is dependent upon the pressure exerted upon her canvas by the wind, it is necessary that the wind strike the sail on one side and fill it, and that it exert this pressure in a constant manner. Therefore, the boat’s bow cannot be kept pointing in the direction of the wind, but must be made to approach it at an angle. This angle, in a good sailing vessel, is one of 45 degrees, or four points by compass.

Let us suppose that the wind is blowing from the North. Now, if the boat’s bow is pointed North the current of air will pass along both sides of her sail and exert no pressure upon the canvas, acting just as it does upon the fly of a flag. But if we turn her head slowly round to the West we will find that the breeze begins to press on the canvas, gradually filling it until when her bow is pointed Northwest, or four points away from the wind, the whole sail will be distended with pressure. She is now said to be on a tack or board, and will move ahead in the direction Northwest.

DIAGRAM C.
BEATING TO WINDWARD—LONG LEG AND SHORT LEG.