Blackbird (land yacht)

Blackbird is an experimental land yacht, built by Rick Cavallaro and John Borton of Sportvision, sponsored by Google and Joby Energy in association with the San Jose State University aeronautics department to demonstrate that it is possible to sail directly downwind faster than the wind. In a test supervised and recognized by the North American Land Sailing Association in July 2010, Cavallaro achieved a speed of 27.7 mph (44.6 km/h) in 10 mph (16 km/h) winds: almost three times the speed of the wind.

In 2006, following a viral internet debate started by Rick Cavallaro as a brain teaser, a propeller-driven land yacht was built and filmed, demonstrating that it is possible to sail 'dead' downwind faster than the wind by the power of the available wind only.

In 2009, professor Drela of MIT worked out the equations for such a device and concluded that one could be built "without too much difficulty". Other researchers arrived at similar conclusions.

In the same year, after being challenged that the video was a hoax, team members Rick Cavallaro and John Borton of Sportvision, sponsored by Google and in association with the San Jose State University aeronautics department, built a test vehicle nicknamed Blackbird. A year later, in 2010, Cavallaro successfully tested the vehicle, achieving more than 2 times the speed of wind, definitively demonstrating that it is possible to build a vehicle which can achieve the claim. A second test with an improved vehicle in 2011 reached close to 3 times the speed of wind.

After proposing the vehicle's design, and presenting the analysis to demonstrate its viability, the Blackbird team learned that others had previously conceived 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.

Bauer observed "a rearward deflection of a foot-long tuft located about 12 feet forward of the propeller plane" thus conclusively demonstrating that his vehicle went faster than the wind (that is, Bauer observed that a streamer located well forward of the propeller was deflected backwards by the apparent wind, meaning that the vehicle was going faster than the real wind). There are no known independent verification to Bauer's claims, although there are several sources of engineering and scientific articles, explaining the theory and physics of such a device. Besides still photography, a film has been found showing it in operation.

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Wikipedia