When you think of sailing, you

probably think of a boat that is propelled by the wind, like the one over here. Did you know that sailing isn’t just for the water? Cars can be powered by the wind. You can see from the pictures below that people have been sailing on land for a long time.

Land Sail Car: A vehicle with wheels that uses a sail and is powered by the wind. Sail Cars, also known as land yachts, used to be used as a mode of transportation. Nowadays, they are mainly used for recreation (just for fun). Here’s what todays Sail Cars look like. The “Greenbird” is a Sail Car that can go 126 miles per hour. That’s faster than most gas powered cars!

NASA is thinking about using a Sail Car to travel on the surface of the planet Venus. Zephyr Land Sailing Rover Image from NASA John Glenn Research Center

Background

Brooklyn Sail Car Sail driven Dutch Cart 17 century

Sail driven vehicle on Kansas Pacific Railway (ca. 1890)

How Land Sailing Works BY LINDA C. BRINSON The Physics of Land Sailing Sailing on water and sailing on land have some things in common, but they also have a lot of differences. In fact, a land sailboat is really more comparable to a glider on wheels than a sailboat. Land sailboats usually have three wheels and one sail. They go too fast to use jibs or spinnakers. (Jibs and spinnakers are the two main types of headsails, or sails used in front of the mainsail, on sailboats.) Made by several manufacturers, land sailboats range in size from a sailboard (sort of like a surfboard with a sail) on wheels to a huge land yacht. In smaller boats, the sailor may sit or lie on the frame. Usually, sailors steer with their feet, moving a T-bar, which basically is two pedals. You push with the right foot to turn left, and with the left foot to turn right. Steering with the feet leaves the hands free to use a rope (also called a line or sheet) to maneuver the sail. The sail is used primarily to adjust speed, not for steering. For some maneuvers, such as going around a racing maker, the land sailor will use the sail, but mostly just to adjust the speed to allow for accurate steering [source: Bassano]. One brand, BloKart, uses a hand-operated tiller, so disabled people can sail. The tiller is a lever that helps steer; on a BloKart, it's attached to the wheels, while on a sailboat, it's attached to the rudder underwater that steers the boat [source: BloKart]. In larger boats, the sailor may be enclosed except for the eyes and top of the head in a long, low craft. These sailors look like they've been stuffed, in a reclining position, into a close-fitting rocket ship or experimental aircraft with a sail. In racing, rules in some classes say that standard boats cannot be modified, while open classes regulate only the size of the sail and allow sailors to experiment with designs. What attracts many people to land sailing is the speed. The speed record, set by Richard Jenkins in March 2009 at Ivanpah Dry Lake on the Nevada-California border, is 126.2 miles per hour (203.1 kilometers per hour). The wind that day was 40 miles per hour (64.4 kilometers per hour). The physics at work is the same as in water sailing, but the results are different because the conditions are different. Forces make things move, and forces can slow or stop moving objects. In sailing, the forces causing motion are the push of the wind on the sail and the pull of the air passing over the curve of the sail, creating lift much like on an airplane wing (but imagine it turned sideways). The forces holding back a water sailboat are the friction of the water on the hull and some friction of air on the boat and sails. Land sailboats can go faster because their wheels face much less friction on dry surfaces. Because the whole boat is exposed to the air, land sailors meet more air friction, but that doesn't slow a boat nearly as much as water friction. Land sailing isn't just sitting back and letting the wind push the boat, though. Sailors must move the boat side to side to maintain that lift. If you try serious land sailing, you're likely to be high as well as dry. The most popular places for land sailing in the United States are on dry lakes in the high deserts in California, Nevada and other Western states.

Dennis Bassano, North American Landing Sailing Association (NALSA) president, estimates that about half of land sailors started out as sailors on water. The rest of them are often people who ride motorcycles or all-terrain vehicles or people who try other sports on America's high deserts and happen to see land sailors while in the area. People see how fast land sailboats can go and want give it a try. There's also a lot of crossover with ice boaters, who in the summer switch out their runners for wheels and take up land sailing. The primary season for land sailing is March through November. In between, rains make the dry lakes muddy bogs. The federal Bureau of Land Management allows land sailing on some public lands and even encourages it. Powered only by wind, land sailing has less impact on the environment than many sports do. Some popular land-sailing sites include: Black Rock Desert-High Rock Canyon Emigrant Trails National Conversation Area in northwestern Nevada Ivanpah Dry Lake, on the California-Nevada border, near Primm, Nev. The Alvord Desert in Oregon El Mirage Dry Lake near Victorville, Calif. People who don't live near dry lakes sometimes sail on beaches at low tide, although most American beaches are too regulated or populated. Some people with smaller boats sail on athletic fields, in parking lots or on airstrips, when they can get permission. It takes more skill to sail in these smaller areas, where the boat is more likely to run into an obstruction. On the dry lakes, the atmosphere is likely to be dusty, and the temperatures can be high. Sailors won't notice the heat once they get going, of course. Unlike in Europe, land sailing sites in the United States tend to be remote, without many amenities. Many people combine sailing with camping. Brinson, Linda C. “How Land Sailing Works.” HowStuffWorks, HowStuffWorks, 5 Oct. 2009,

adventure.howstuffworks.com/outdoor-activities/urban-sports/land-sailing.htm

Wind-powered vehicle

Wind-powered vehicles derive their power from sails, kites or rotors and ride on wheels—which may be linked to a wind-powered rotor—or runners. Whether powered by sail, kite or rotor, these vehicles share a common trait: As the vehicle increases in speed, the advancing airfoil encounters an increasing apparent wind at an angle of attack that is increasingly smaller. At the same time, such vehicles are subject to relatively low forward resistance, compared with traditional sailing craft. As a result, such vehicles are often capable of speeds exceeding that of the wind. A Belgian Class 3 competition land yacht

Rotor-powered examples have demonstrated ground speeds that exceed that of the wind, both directly into the wind and directly downwind by transferring power through a drive train between the rotor and the wheels. The wind-powered speed record is by a vehicle with a sail on it, Greenbird, with a recorded top speed of 202.9 kilometers per hour (126.1 mph). Other wind-powered conveyances include sailing vessels that travel on water, and balloons and sailplanes that travel in the air, all of which are beyond the scope of this article. Sail-powered Sail-powered vehicles travel over land or ice at apparent wind speeds that are higher than the true wind speed, close-hauled on most points of sail. Both land yachts and ice boats have low forward resistance to speed and high lateral resistance to sideways motion.

Theory Apparent wind on an iceboat. As the iceboat sails further from the wind, the apparent wind increases slightly and its speed is highest at C on the broad reach.[1] Aerodynamic forces on sails depend on wind speed and direction and the speed and direction of the craft ( V ). The direction that the craft is traveling with respect to the true wind (the wind direction and speed over the surface – V ) is called the point of sail. The speed of the craft at a given point of sail contributes to the apparent wind ( V )—the wind speed and direction as measured on the moving craft. The apparent wind on the sail creates a total aerodynamic force, which may be resolved into drag—the force component in the direction of the apparent wind—and lift—the force component normal (90°) to the apparent wind. Depending on the alignment of the sail with the apparent wind, lift or drag may be the predominant propulsive component. Total aerodynamic force also resolves into a forward, propulsive, driving force—resisted by the

medium through or over which the craft is passing (e.g. through water, air, or over ice, sand)—and a lateral force, resisted by the wheels or ice runners of the vehicle. Because wind-powered vehicles typically sail at apparent wind angles aligned with the leading edge of the sail, the sail acts as an airfoil and lift is the predominant component of propulsion. Low forward resistance to motion, high speeds over the surface, and high lateral resistance help create high apparent wind speeds—with closer alignment of the apparent wind to the course traveled for most points of sail—and allow wind-powered vehicles to achieve higher speeds than conventional sailing craft. Land yacht Land sailing has evolved from a novelty, since the 1950s, primarily into a sport. The vehicles used in sailing are known as land or sand yachts. They typically have three (sometimes four) wheels and function much like a sailboat, except that they are operated from a sitting or lying position and steered by pedals or hand levers. Land sailing is best suited for windy flat areas; races often take place on beaches, airfields, and dry lake beds in desert regions. Greenbird, a sail-powered vehicle sponsored by Ecotricity, broke the land speed world record for a wind-powered vehicle in 2009 with a recorded top speed of 202.9 kilometers per hour (126.1 mph), beating the previous record of at 116 miles per hour (187 km/h), set by Schumacher from the United States, riding Iron Duck in March 1999. Ice boat International DN ice boat Iceboats designs are generally supported by three skate blades called "runners" supporting a triangular or cross-shaped frame with the steering runner in front. Runners are made of iron or steel and sharpened to a fine edge, most often cut to an angled edge of 90 degrees, which holds onto the ice, preventing slippage sideways from the lateral force of the wind developed by the sails. Once the lateral force has been effectively countered by the runner edge, the remaining force of "sail-lift" vacuums the boat forward with significant power. That power increases as the speed of the boat increases, allowing the boat to go much faster than the wind. Limitations to iceboat speed are windage, friction, the camber of the sail shape, strength of construction, and quality of the ice surface. Iceboats can sail as close as 7 degrees off the apparent wind. Ice boats can achieve speeds as high as ten times the wind speed in good conditions. International DN iceboats often achieve speeds of 48 knots (89 km/h; 55 mph) while racing, and speeds as high as 59 knots (109 km/h; 68 mph) have been recorded.

Kite-powered Kite-powered vehicles include buggies that one can ride in and boards that one can stand on as it slides over snow and ice or rolls on wheels over land. Snow kiters travel over snow or ice.

Theory A kite is a tethered air foil that creates both lift and drag, in this case anchored to a vehicle with a tether, which guides the face of the kite to achieve the best angle of attack. The lift that sustains the kite in flight is generated when air flows around the kite's surface, producing low pressure above and high pressure below the wings. The interaction with the wind also generates horizontal drag along the direction of the wind. The resultant force vector from the lift and drag force components is opposed by the tension of one or more of the lines or tethers to which the kite is attached, thereby powering the vehicle. Kite buggy A kite buggy is a light, purpose-built vehicle powered by a power kite. It is single-seated and has one steerable front wheel and two fixed rear wheels. The driver sits in the seat located in the middle of the vehicle and accelerates and slows down by applying steering maneuvers in coordination with flying maneuvers of the kite. Kite buggies can reach 110 kilometers per hour (68 mph). Kite board Kite boards of different description are used on dry land or on snow. Kite land-boarding involves the use of a mountain board or land board—a skateboard with large pneumatic wheels and foot-straps. Snow kiting is an outdoor winter sport where people use kite power to glide on a board (or skis) over snow or ice.

Rotor-powered Rotor-powered vehicles are wind-powered vehicles that use rotors—instead of sails—which may have a shroud around them (ducted fan) or constitute an unduct propeller, and which may adjust orientation to face the apparent wind. The rotor may be connected via a drive train to wheels or to a generator that provides electrical power to electric motors that drive the wheels. Other concepts use a vertical axis wind turbine with airfoils that rotate around a vertical axis. Theory Gaunaa, et al. describe the physics of rotor-powered vehicles. They describe two cases, one from the vantage point of the earth and the other from the vantage point of the air stream and come to the same conclusions from both frames of reference. They conclude that (apart from forces that resist forward motion): There is no theoretical upper limit to how fast a rotor-driven craft can go directly upwind. Likewise, there is no theoretical upper limit to how fast a rotor-driven craft can go directly downwind. These conclusions hold both for land and water craft. The rotor-powered InVentus Ventomobile racing at the Aeolus Race 2008

Required for wind-powered vehicle (or water craft) motion are: Two masses moving with respect to each other, e.g. the air (as wind) and the earth (land or water). The ability to change the velocity of either mass with a propeller or a wheel. In the case of a rotor-powered vehicle, there is a drive linkage between the rotor and the wheels. Depending on one's frame of reference—the earth's surface or moving with the air mass—the description of how available kinetic energy powers the vehicle differs: As seen from the vantage point of the earth (e.g. by a spectator), the rotor (acting like a wind turbine) decelerates the air and drives the wheels against the earth, which it accelerates imperceptibly. As seen from the vantage point of the air stream (e.g. by a balloonist), the wheels impede the vehicle—decelerating the earth imperceptibly—and drive the rotor (acting like a propeller), which accelerates the air and propels the vehicle. The connection between the wheels and the rotor causes the rotor to rotate faster with increasing vehicle speed, thereby allowing the rotor blades to continue to obtain forward lift from the wind (as seen from the ground) or to propel the vehicle (as seen from the air stream). In 2009, Mark Drela—an MIT professor of aeronautics and astronautics—produced the first equations, demonstrating the feasibility of "Dead-Downwind Faster Than The Wind (DDWFTTW)".

Fixed-course vehicles Several competitions have been held for rotor-powered vehicles. Notable among them is Racing Aeolus, an event held annually in the Netherlands. Participating universities build entries to determine the best and fastest wind-powered vehicle. The rules are that the vehicles ride on wheels, with one driver, propelled by a rotor, coupled to the wheels. Temporary storage of energy is allowed, if empty at the beginning of the race. Charging the storage device is counted as race time.

Competition rotor-powered vehicles: Ventomobile and winD TUrbine set for a drag race Racing takes place towards the wind. Vehicles are judged by their fastest run, innovation, and the results of a series of drag races. In 2008, entrants were from: Stuttgart University, the Flensburg University of Applied Sciences, the Energy Research Centre of the Netherlands, the Technical University of Denmark, the University of Applied Sciences of Kiel and the Christian Albrechts University of Kiel. Two top performers have been the "Ventomobile" and Spirit of Amsterdam (1 and 2). Ventomobile The Ventomobile was a wind-powered lightweight three-wheeler designed by University of Stuttgart students. It had a carbon-fiber rotor support that was directed into the wind and variably pitched rotor blades that adjust for wind speed. Power transmission between the rotor and the driving wheels was via two bicycle gearboxes and a bicycle chain. It won the first prize at the Racing Aeolus held at Den Helder, Netherlands, in August 2008.

Spirit of Amsterdam The wind-powered land vehicles Spirit of Amsterdam and Spirit of Amsterdam 2 were built by the Hogeschool van Amsterdam (University of Applied Science Amsterdam). In 2009 and 2010 the Spirit of Amsterdam team won first prize at the Racing Aeolus held in Denmark. The Spirit of Amsterdam 2 was the second vehicle built by the Hogeschool van, Amsterdam. It used a wind turbine to capture the wind velocity and used mechanical power to propel the vehicle against the wind. This vehicle was capable of driving 6.6 metres per second (15 mph) with a 10 meters per second (22 mph) wind. An onboard computer automatically shifted gears to achieve optimum performance.

Straight-line vehicles Some wind-powered vehicles are built solely to demonstrate a limited principle, e.g. the ability to go upwind or downwind faster than the prevailing windspeed. In 1969, Mark Bauer—a wind tunnel engineer for the Douglas Aircraft Company—built and demonstrated a vehicle to go directly downwind faster than the windspeed, which was recorded in a video. He published the concept in the same year.

Land yacht, Blackbird, straight-line rotor-powered vehicle, was designed to go faster than the wind, dead downwind. In 2010, Rick Cavallaro—an aerospace engineer and computer technologist—built and tested a wind-rotor-powered vehicle, Blackbird, with cooperation with the San Jose State University aviation department in a project sponsored by Google, to demonstrate the feasibility of going directly downwind faster than the wind. He achieved two validated milestones, going both directly downwind and upwind faster than the speed of the prevailing wind. Downwind—In 2010, Blackbird set the world's first certified record for going directly downwind faster than the wind, using only wind power. The vehicle achieved a dead downwind speed of about 2.8 times the speed of the wind. In 2011 a streamlined Blackbird reached close to 3 times the speed of wind. Upwind—In 2012, Blackbird set the world's first certified record for going directly upwind faster than the wind, using only wind power. The vehicle achieved a dead upwind speed of about 2.1 times the speed of the wind. “Wind-Powered Vehicle.” SailMagazine.com, Apr. 2010, www.sailmagazine.com/running-faster-wind.