Blackbird (land yacht)
Encyclopedia
The Blackbird is a propeller-driven land yacht that was developed specifically to prove that it is possible to sail dead downwind faster than the wind ("DDWFTTW"), steady state, powered by the wind only.A good account of the history of the project, with an explanation of how the device works (and why it does not violate any laws of physics) is given in In essence, the project started as a brain-teaser that went viral across Internet forums. The authors of the brain-teaser soon learned that Andrew Bauer had built a similar vehicle (see below). As the result of the Internet debates, a member of the team built and demonstrated a working model. A video of that model at work was posted on the Internet and attracted a great deal of attention. In order to prove that the video was not a hoax, team members Rick Cavallaro and John Borton designed, built, and operated the full-scale version, that is, the Blackbird. At first, one might think that such a feat is impossible, because it violates some physical law. But in fact no physical laws are violated. In 2009, an MIT professor had worked out the equations for such a device and he also worked out whether such a device could be built in practice; he concluded that "the DDWFTTW condition V/W > 1 is achievable with a wheeled vehicle without too much difficulty." Other researchers arrived at similar conclusions.Apparently Andrew Bauer built the first successful cart able to progress dead downwind faster than the wind. He did this in 1969 to settle a friendly wager with a colleague aero engineer. The wager was based on a claim in a student's paper that such a device could be built, see . And such a device was built and tested in 2006.
Conventional sail-driven boats can achieve downwind velocity made good greater than the speed of the wind,During the 2009 land speed record, the sand yacht Greenbird
was proceeding at about 3 times the speed of the wind on a course about 120 degrees off the true wind, see . Thus, its speed made good downwind was about 1.5 times the speed of the wind.During a training run the catamaran Alinghi 5
, one of the competitors for the 2010 America's Cup, covered 20 nautical miles to windward and back in 2.5 hours in 8-9 knot winds, so its average velocity made good was 16 knots, about 1.9 times wind speed, see .During the first race of the 2010 America's Cup, the winning yacht USA sailed 20 nautical miles to windward in 1 hour 29 minutes, in winds of 5 to 10 knots. Thus its velocity made good upwind was about 1.8 times windspeed, consistent with being able to sail about 13 degrees off the apparent wind when sailing upwind. It sailed 20 nautical miles downwind in 1 hour 3 minutes, so its velocity made good downwind was about 2.5 times windspeed, consistent with being able to sail about 14 degrees off the apparent wind when sailing downwind. See ; see also ; see also ; see also Other sailboats (such as the 18ft Skiff) can make good downwind at speeds faster than the wind; see ; see also the polar chart in section 24.1 (Figure 24.1) of ; see also the polar chart at page 123 of . The polar chart in Figure PS1 of the cited book High Performance Sailing shows that boats that were sailing in 1996 were able to make good downwind at about 1.5 times the speed of the wind. but cannot move faster than the wind while moving in the same direction that the wind is blowing ("dead downwind").
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.
On July 2, 2010, Blackbird set the world's first certified record for going directly downwind, faster than the wind, using only power from the wind. The yacht achieved a dead downwind speed of about 2.8 times the speed of the wind.
Conventional sail-driven boats can achieve downwind velocity made good greater than the speed of the wind,During the 2009 land speed record, the sand yacht Greenbird
Greenbird
The Ecotricity Greenbird is a wind-powered vehicle that broke the land speed record for the fastest wind-powered vehicle at the dry Ivanpah Lake on March 26, 2009. It was built by the British engineer Richard Jenkins...
was proceeding at about 3 times the speed of the wind on a course about 120 degrees off the true wind, see . Thus, its speed made good downwind was about 1.5 times the speed of the wind.During a training run the catamaran Alinghi 5
Alinghi 5
The Alinghi 5 is a LWL, beam sloop-rigged catamaran built by Alinghi for the 33rd America's Cup.It was launched on 8 July 2009 being lifted from the construction shed in Villeneuve, Vaud by a Mil Mi-26 helicopter and carried thereby to Lake Geneva. It was subsequently carried to Genoa, Italy...
, one of the competitors for the 2010 America's Cup, covered 20 nautical miles to windward and back in 2.5 hours in 8-9 knot winds, so its average velocity made good was 16 knots, about 1.9 times wind speed, see .During the first race of the 2010 America's Cup, the winning yacht USA sailed 20 nautical miles to windward in 1 hour 29 minutes, in winds of 5 to 10 knots. Thus its velocity made good upwind was about 1.8 times windspeed, consistent with being able to sail about 13 degrees off the apparent wind when sailing upwind. It sailed 20 nautical miles downwind in 1 hour 3 minutes, so its velocity made good downwind was about 2.5 times windspeed, consistent with being able to sail about 14 degrees off the apparent wind when sailing downwind. See ; see also ; see also ; see also Other sailboats (such as the 18ft Skiff) can make good downwind at speeds faster than the wind; see ; see also the polar chart in section 24.1 (Figure 24.1) of ; see also the polar chart at page 123 of . The polar chart in Figure PS1 of the cited book High Performance Sailing shows that boats that were sailing in 1996 were able to make good downwind at about 1.5 times the speed of the wind. but cannot move faster than the wind while moving in the same direction that the wind is blowing ("dead downwind").
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.
On July 2, 2010, Blackbird set the world's first certified record for going directly downwind, faster than the wind, using only power from the wind. The yacht achieved a dead downwind speed of about 2.8 times the speed of the wind.