How Sailing Works
If you hold your hand out the window of a moving car, you can feel the force of the wind lifting your hand. This is the same force that “pulls” a sailboat forward when the wind comes over the side of the boat.
PULL MODE
Your sail is much more efficient at using the wind than your hand. It is shaped to bend the wind as it flows by, creating higher pressure on the inside of the sail U and lower pressure on the outside U, thus creating lift. The lift the sail creates “pulls” the boat forward and sideways. The boat’s keel keeps the boat from being pulled sideways through the water.
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HOW A FOIL WORKS If sails are a boat’s engine, then the centerboard and rudder are the boat’s tires: they provide the grip necessary to keep you on track. The centerboard and rudder create lift in much the same way that a sail does. When a sailboat is sailing upwind, it continually slips slightly to leeward.
When sailing downwind, sideways force from the sails is lessened so you do not need as much centerboard. Raising the centerboard for downwind sailing reduces the amount of drag, which increases boat speed.
While a centerboard’s primary responsibility is resistance to side-slipping, a rudder’s primary function is steering. By moving the rudder to one side of the boat or the other, pressure on the rudder blade provides the force to steer the boat. Remember that every time the rudder is moved from a neutral position amidships, the force to steer will also slow the boat down. Less helm usage usually allows the boat to sail faster.
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