Sailing faster than the wind is the technique by which vehicles that are powered by sails (such as sailboats, iceboats and sand yachts) advance over the surface on which they travel faster than the wind that powers them. Typically, such devices cannot travel faster than the wind when sailing dead downwind using simple square sails that are set perpendicular to the wind. They require sails set at an angle to the wind, which utilizes the lateral resistance of the surface on which they sail (for example the water or the ice) to maintain a course at some other angle to the wind.
For those craft it is impossible to sail dead downwind faster than the wind because the apparent wind will be zero if the speed of the vehicle equals the speed of the wind. However, certain sailing craft (such as ice boats and high performance catamarans) can achieve overall downwind speeds faster than the wind by tacking back and forth across the wind: they do this by using the surface on which they sail to capture the energy of the wind. Similarly, it is possible to sail dead downwind faster than the wind if a mechanical device is used to transfer energy from the surface on which the machine is moving in order to capture the energy of the wind and use it (not through a sail). By using a propeller instead of a conventional sail, and coupling the propeller to its wheels, a land yacht can proceed dead downwind faster than the wind.
Following an internet debate, started as a brain teaser, a team of students conceived and built a wind turbine (propeller) based land yacht, with the turbine coupled to its wheels through transmission with gears, and filmed it. After being challenged that the film was a hoax, some of the team members developed the Blackbird land yacht in a project sponsored by Google and with the San Jose State University aviation department. During the development period a MIT professor published the equations for such a vehicle. He concluded that it was possible and would not be difficult to create. His equations and conclusions were supported by several others.
Such a device was built and tested in 2006. After proposing the vehicle’s design, and presenting the analysis to demonstrate its viability, the Blackbird team learned that others had previously conceived of and built similar designs – most notably Andrew Bauer of Douglas Aircraft built and demonstrated such a vehicle in 1969, based on an analysis presented in a student’s paper from some 20 years earlier. In 2010, the Blackbird set the world’s first certified record for going directly downwind, faster than the wind, using only power from the available wind. The yacht achieved a dead downwind speed of about 2.8 times the speed of the wind. In 2012, it set the world’s first certified record for going directly upwind, without tacking, using only power from the wind. The yacht achieved a dead upwind speed of about 2.1 times the speed of the wind.
The Daily Omnivore 
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