PART 1 SAILBOAT DYNAMICS


A sailboat is a wonderful combination of balancing forces. One of the most important is the sideways force resulting from the wind acting on the sails and rig. Opposing this force is the sideways resistance to the water offered by the keel and underwater part of the hull. (See illustration to the right.)


Tese same two forces affect the boat’s course. When the point of the force on the sails (Center of Effort or CE) matches the point of the force on the boat’s underbody (Center of Lateral Resistance or CLR), the boat moves forward in a straight line. When these focal points shiſt forward or back, the boat wants to turn. (See illustrations to the right.) You can actually steer the boat with the sails alone. Try it!


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For a complete introduction to sailing and sail trim, see US Sailing’s Basic Keelboat book.


CE CLR CE CLR CLR CE Balanced


The opposing forces of wind (CE) and water (CLR) are balanced and the boat moves forward.


Heading Down


When the mainsail is luffed, the CE moves forward and forces the bow away from the wind. To resist the boat’s turning away from the wind, the helmsman counteracts by steering toward the wind (lee helm) enough to maintain a straight course.


18 Heading Up


When the jib is luffed, the CE moves backward and forces the bow toward the wind. To resist the boat’s turning toward the wind, the helmsman coun- teracts by steering away from the wind (weather helm) enough to maintain a straight course.


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