today
9 a.m. Doris Niles Humboldt County Science Fair Humboldt State University
read >10 a.m. Annual Juggling Festival Humboldt State University
read >10:30 a.m. Green Jobs Fair College of the Redwoods Downtown Site
read >11 a.m. Baby Read and Grow Program Humboldt County Library
read >1 p.m. Apple Solutions for Small Business See Event Description
read >4 p.m. Young Parent Support Group College of the Redwoods Kinship Site
read >6 p.m. The Tumbleweeds (cowboy songs) Chapala Cafe
read >6 p.m. Bon Swing Libation
read >6 p.m. Annual Pisces Party See Event Description
read >6 p.m. Annual Pisces Party See Event Description
read >7 p.m. The Big Lebowski Arcata Theater Lounge
read >7 p.m. DJ Ray Boiler Room
read >7:30 p.m. Arianna String Quartet Calvary Lutheran Church
read >7:30 p.m. A Midsummer Night's Dream Arcata High School
read >8 p.m. Eureka Symphony Concert Arkley Center for the Performing Arts
read >8 p.m. Humboldt Folkdancers Arcata Presbyterian Church
read >8 p.m. On the Wings of a Dove Carlo Theater (Dell'Arte)
read >8 p.m. Antigone College of the Redwoods
read >8 p.m. So Hum Tales Mateel Community Center
read >8 p.m. Gentle Thunder Arcata Playhouse
read >8:30 p.m. The Last Minute Men (international) Cafe Mokka
read >9 p.m. Taxi (rock & roll) Bear River Casino
read >9 p.m. Vintage Soul (R&B) Cher-Ae-Heights Casino
read >9 p.m. Bump Foundation Pearl Lounge
read >9 p.m. The Brothers Comatose (folk) Six Rivers Brewery
read >9 p.m. The Malone (rock Red Fox Tavern
read >10 p.m. Music by DJ Sidelines
read >10 p.m. DJ Ninja Retro Dance Party Aunty Mo's Lounge
read >previous columns
April 3, 2008
Ancient Mariners
Sailing is an ancient enterprise. Humans used the wind to ...
read >March 27, 2008
Hunting Worms
I recently went big-game hunting in the bay for a ...
read >March 20, 2008
Tsunami Terrors
Understanding the nature of tsunamis could save your life. They ...
read >
Photos
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The vector-sum of forces on sail and keel is balanced by the resistance of moving the boat through water. Diagram by Don Garlick.
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Speed is a function of the boat's angle to the wind. Diagram by Don Garlick.
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The length of the yacht is important. Diagram by Don Garlick.
Sailing
By Don Garlick
The physics of sailing is outlined in the first diagram, showing the equilibrium between forces. The vector-sum of forces on sail and keel is balanced by the resistance of moving the boat through water.
The speed of a typical 10-meter yacht in winds of 10 and 20 knots, as a function of its angle to the wind, is shown in the second diagram (1 knot = 1.15 mph and 1 mile = 1.6 km). As shown in the third diagram, the length of the yacht is important because the speed of the induced bow wave varies with the wave's length. It is difficult for a boat to exceed the speed of a wave whose wavelength is longer than the boat, because the boat is then attempting to climb up the wave. With sufficient power, however, a speed-boat can ride up upon its bow wave and effectively hydroplane.
Although the maximum speed of a typical yacht is less than the wind speed, high-tech catamaran yachts have reached speeds about twice that of the wind. A windsurfer narrowly beat the yachting record this year with a speed of 49 knots (56 mph). The land yacht record is 117 m.p.h. in 30 m.p.h. winds!
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