Sailing Theory, Sailing Terms and Weather

by Linda Cullum

Sailing Theory The sum of all wind pressure on the sail is called wind force. The center of that force, which is above the water, is called the center of effort (CE). The center of the force below the surface of the water is calledthe center of lateral resistance (CLR). This is the point where all the boat's resistance to sideways pressure is concentrated. A boat performs best when the two forces are in balance. This is when they are positioned one over the other in a vertical line through the boat's sail and hull. Your job as a sailor is to keep these two forces in proper balance so that your boat will sail correctly. You keep the boat balanced by shifting your weight and adjusting your sail.

Your boat has weather helm when you have to constantly pull the tiller towards you to keep the boat straight on course. Lee helm is when you do the opposite; pushing the tiller towards the sail. Most boats are designed to have a little weather helm. However, too much of it can make sailing difficult in anything other than light breezes. If your boat has a lot of weather helm, it means the CE and the CLR are not in alignment.There is more sail pressure aft of the CLR than forward of it.

To correct the balance, 1. Shift your weight aft (back towards the stern). 2. Pull up the centerboard. 3. If your boat has a jib, ease (let out) the mainsail. 4. Try any combination of these.

Weather- The Sea Breeze

As a sailor you should know about local winds. The cause of these winds is difference in temperature; cold air is heavier than warm air. The most popular of these local winds is the sea breeze. Warm air over the land rises...And is replaced by cooler air sinking over the ocean. At night the opposite happens. The land quickly loses its heat at night and oftenfalls to a lower temperature than the water. This results in a light offshore evening wind. On a lake or river, the warm air can rise at the edges to be replaced by the cool air over the water. This can result in a nice breeze for sailing.

Forcast for a Typical Sea Breeze Day: Morning Very Light Winds -No Weather Systems Near -Clear Sky -High Temperatures But Cooler Near the Shore

Afternoon: Wind coming from water starting Midday -Cumulus Clouds over land -Clear over water- Winds Speeds 8 - 12 knots

Evening: Winds Decreasing as sun slips over horizon.

Sailing Terms

Amidships- the middle of the boat.

Backwind- the wind flowing off the sail.

Close Hauled- one of the points of sail; sailing as close to the wind as possible.

Dead Astern- straight behind

Flaking- Folding the sail.

Glide Zone- the distance it take a boat to stop after turningb head to wind.

Heave To- to head the boat into the wind in order to slow it down or stop it.

About the Author

Linda Cullum is from Cape Cod, MA, with a second home in Vermont. She is the author of Learn to Sail! with Multimedia! an Interactive Sailing training CDROM which teaches all aspects of Sailing including Knots, Piloting, Rules of the Road, Weather with digital video from Sail Magazine, narration, animation and quizzes. Visit her site at http://learntosail.net Happy Sailing_/)__

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