C. C. Brooks
The wind has four direct effects on a sail boat which must be understood by the amateur sailor before he can begin to see why his boat performs differently under different conditions of wind and sailing course.
The wind drives the boat ahead - most important of all; it also drives it laterally or, to speak in a nautical term, causes it to "make leeway " ; it heels the boat over and lastly turns it around, according to the balance of her sails, distribution of weight, and what is known as the " center of lateral resistance." The proper handling of sails and rudder is what enables the sailor to so utilize these effects of the wind that he may sail his boat in any direction.
The propelling effect is the one most utilized, and it is for this reason that every boat is constructed to offer the least resistance to its forward movement with as little friction as possible.
Leeway is one effect to be avoided, and for this purpose boats are given either deep, stationary keels or center boards, or some other device for providing an extensive lateral surface below the water.
Heeling and the stability of a boat go hand in hand. The boat must be prevented from capsizing, and this is done either by putting lead or iron on the keel, or carrying ballast in the hull in order to lower the center of gravity, or by building a broad and shallow boat such as the cat boat, which is very stiff in a breeze and does not heel readily, but when a certain point has been reached, is apt to capsize quickly in the hands of an unskilful sailor.
The fourth effect is that of turning the boat around. This is done when the center of effort on the sails does not come on a line with the center of lateral resist-tance. This is always the case in a poorly balanced boat. A well balanced boat requires very little movement of the rudder to hold to a course.
Any novice can understand how a sailing boat can travel with the wind, but why it should go forward when the sails are close hauled is a question of dynamics which we will not try to explin in this short article. An easily understood explanation of why boats go ahead instead of sideways can be made by taking a V-shaped block of wood and pressing it between the thumb and forefinger. If sufficient force is used it shoots forward quickly. The thumb may be likened to the wind and the forefinger to the water on the opposite side of the boat. The pressure caused by the wind pushing the boat against the water on the opposite side causes the boat to go forward,
The ceuter of effort and center of lateral resistance must be understood in the handling of a sail boat. The center of effort is the center of the total sail area. If, for example, this comes forward of the center of lateral resistance when the boat is sailing with the wind abeam, then the side pressure on the sails will turn the boat's bow in the direction towards which the wind is blowing, or away from the wind, and a boat doing this is said to carry a " lee helm."
Ou the other hand, if the center of lateral resistance is further forward than the center of effort, the wind will swing the boat in the direction in which it is blowing, thus throwing the bow up into the wind. A boat doing this is said to carry a weather helm. Every sailing boat should be so rigged as to carry a little weather helm as, if struck by squall under those conditions, it will luff quickly up into the wind and so be in safety, while if the lee helm is carried, the boat will fall off before the wind, presenting a broadside to wind and wave which is very apt to cause it to cap-size.
Too much weather helm is also to be avoided as it makes it necessary to keep the rudder over at a sharp angle and retards the progress of the boat.
To reduce weather helm, move the ballast aft or shorten the after canvas or increase the forward canvas by setting a larger jib. If a boat carries a lee helm, shift the ballast forward or reduce the area of the head canvas.
In considering the action of the rudder, the amateur sailor should bear in mind that as the boat is turned by the rudder it swings as on a pivot. The water, pressing against one side of the rudder, pushes the stern of the boat away from that side.
The pivot or turning point is always well forward of the center. This is a fact that should be remembered when steering close to a boat or other object. Don't delay turning out of the way too long or the very act of turning your boat will throw the stern over sufficiently to cause the collision you are trying to avoid.