Several comments in this thread say something to the effect of "sailboats do this all the time" or "sailors have known this for years."
Sailboats do not sail faster than the wind when sailing dead downwind. High-performance sailboats absolutely do sail faster than the wind when sailing upwind or on a reach. This is a result of the apparent wind velocity (the velocity measured on the boat) increasing as the boat accelerates into the wind. This apparent wind is what powers the sails -- more apparent wind, higher boat speed. Terry Tao's explanation is excellent: http://terrytao.wordpress.com/2009/03/23/sailing-into-the-wi...
A recent real-world example is the boat that won the America's Cup this time around, Oracle's 90-foot trimaran BOR 90. BOR 90 handily sails several times faster than the wind upwind. Watch chase boats try and keep in a mere 10 or 12 knots of wind as the boat is going 32 knots: http://en.wikipedia.org/wiki/USA_17_(yacht)
Downwind is a totally different story. As you approach dead-downwind you accelerate with the wind until your boat speed reaches the speed of the wind and your apparent wind approaches zero.
As for sailors knowing about the effect, I can assure you it is just as counter-intuitive to us as anyone else. Maybe more so since we spend a lot of time observing how boats behave downwind. I've raced in San Francisco for more than a decade and had this discussion with maybe a dozen racing sailors in the last few months. Things got heated every time. No intuition to be found.
[Edit: corrected sloppy about dead-downwind vs just downwind. As commenters have noted, sailboats will happily go faster than the wind at angles below 90 degrees, but not at 180 degrees.]
Nice links, thanks. I respectfully disagree with the upwind/downwind speeds though. In my experience the most force on the sailboat/windsurfer (and resulting speed of the boat) comes from sailing at a broad reach, roughly 45% downwind. Linked from your USA_17 article:
One's intuition works if you think about it like a heavy brick pressing on a slippery wedge shaped object between the brick and the floor. The wedge will "squirt" out the side at several times the velocity the brick is moving towards the floor.
Sailboats can't sail directly downwind (say, within 5 deg. of directly downwind) faster than the wind. However, they can and do travel downwind with net speeds faster than the wind. Indeed, "speed made good" directly downwind for sailboats and iceboats has been measured at several times that of wind speed. This has been recorded in the America's cup race, for example.
So this result shouldn't really be that unexpected. Sailboats can't sail directly downwind faster than the wind, but they can travel downwind faster than the wind.
To expand on this slightly - sailboats can "make good" downwind at higher than windspeed by reaching at an angle to the wind, then gybing back the other way. If the boat can reach at a high enough speed then they can "make good" the extra distance.
Sailboats do not sail faster than the wind when sailing dead downwind. High-performance sailboats absolutely do sail faster than the wind when sailing upwind or on a reach. This is a result of the apparent wind velocity (the velocity measured on the boat) increasing as the boat accelerates into the wind. This apparent wind is what powers the sails -- more apparent wind, higher boat speed. Terry Tao's explanation is excellent: http://terrytao.wordpress.com/2009/03/23/sailing-into-the-wi...
A recent real-world example is the boat that won the America's Cup this time around, Oracle's 90-foot trimaran BOR 90. BOR 90 handily sails several times faster than the wind upwind. Watch chase boats try and keep in a mere 10 or 12 knots of wind as the boat is going 32 knots: http://en.wikipedia.org/wiki/USA_17_(yacht)
Downwind is a totally different story. As you approach dead-downwind you accelerate with the wind until your boat speed reaches the speed of the wind and your apparent wind approaches zero.
As for sailors knowing about the effect, I can assure you it is just as counter-intuitive to us as anyone else. Maybe more so since we spend a lot of time observing how boats behave downwind. I've raced in San Francisco for more than a decade and had this discussion with maybe a dozen racing sailors in the last few months. Things got heated every time. No intuition to be found.
[Edit: corrected sloppy about dead-downwind vs just downwind. As commenters have noted, sailboats will happily go faster than the wind at angles below 90 degrees, but not at 180 degrees.]