TACKING. Tire evolutions of a ship when contending with an adverse wind are called tacking ; and the course upon which a ship lies is called its " tack," and whether the wind blow on the star board- or port-side, these are called starboard or port tacks. In endea vouring to move a ship under sail towards the point from which the wind blows, she must necessarily be close hauled, that is, her sails must be so braced as to enable her to proceed as near the wind as possible.
We may illustrate the operation of tacking by reference to a similar movement iu ourselves, whether on foot or horseback, when wo mount a steep incline on shore; for, instead of facing the inclination of the hill in its abruptness, we sidle along upwards in a zig-zag direc tion until the summit is reached,—and thus it is with tacking at sea; where, however, we use horizontal angles instead of the vertical ones on land.
The motion of a ship in thus beating to windward (as the whole evolution is called) is considerably affected by the form of the ship herself ; for barges, and flat or round-bottom vessels make great lee way, or are driven bodily from the wind, and the actual course sailed is upon a line which is the resultant of two forces. For supposing the wind to be acting in the direction indicated by the arrow in the diagram, its power upon the mass of broadside and sails will have a with a rising floor like yachts, cutters, &e., as they offer more vertical resistance to the water in arresting the lateral drift A B. Vessels having no keel or deadwood are generally furnished with what is called a " lee-board," which working on a strong pin, as at c in the figure, is let down below the bottom on the lee side to prevent too much leeway when tacking to windward.
In order to very briefly explain the operation of tacking (or as it is also called " heaving suppose the figure below to represent aship at a, beating towards the direction of the wind x, and close hauled tendency to drive it from A towards ir (this is called leeway), while the action of the sails in their obliquity to the keel drives the body also forward in the line of keel Ac. Now compounding these two forces,
A B and C D, we have the parallelogram A D as the resultant, while the amount of leeway would be measured by A B, and its angle would be E A r. Hence tacking is more advantageous to sharp-bottomed vessels on the port tack accordingly, the tiller is put over towards y (" hard a-lee "), which causes the rudder to bring the ship's head to wind, as at b, or throws her into " stays; " just before she reaches this position, the afteryards (on the main and mizen masts) are hauled aback and then braced as at c, and as soon as the ship's head is found to be about five points from the wind the head yards are braced round likewise, and the ship fills with the wind upon the starboard side, as seen at d, and she is now on the starboard tack. It is at times a perilous evolu tion, and if there be much sea on is found impracticable. To insure success however under ordinary circumstances, the helmsman just previously keeps the sails " clean full " (as the expression is), lest the ship's velocity be insufficient to bring her head to wind ; if it be so, her head " falls off" again, and she is said to have missed stays ; this is frequently caused by the helmsman neglecting to shift the helm when the ship acquires stern-way. When, from having lost all velocity, she will neither stay nor fall off, she is said to be " jammed up in the wind," or "in irons," the remedy being to brace the head-yards aback and " pay off." If such happen when too near shore the danger is imminent. (VEmenxe.)