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Background 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. Sail driven Dutch Cart Sail driven vehicle on Kansas Brooklyn Sail Car 17 century Pacific Railway (ca. 1890) 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 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.

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