Sailing
(April 10, 2008) 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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Today
Winter Classic Table Tennis Tournament
sports / 11:30 a.m. Arcata Community Center, 321 Community Parkway. Compete in 12 and under, beginners, intermediate, advanced or seniors groupings. Prizes for winners. $10/$5 kids 12 and under. 601-5447.
Audubon Society Field Trip
outdoors / 9 a.m. Humboldt Bay National Wildlife Refuge, 1020 Ranch Road, Loleta. Meet at Refuge Visitor Center off Hookton Road. Leisurely, two- to three-hour trip intended for people wanting to learn birds of Humboldt Bay area. 822-3613.
Open Celtic Music Session
music / 3 p.m. Cafe Veritas/Mosgo's, 180 Westwood Center, Arcata. Informal monthly gathering of musicians playing Irish and other Celtic music. Hosted by Seabury Gould. seaburygould.com. 845-8167.
Nonviolence Action Camp
etc. / 10 a.m. Chinmaya Mission near Piercy. Weekend-long direct action orientation features workshops, role playing, seminars, ceremonies and field trips. Bring food, bedding, warm clothes, signs, banners, bikes, drums, acoustic instruments. Pre-register. saverichardsongrove.org. 932-5898.
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