A Kammback—also known as a Kamm tail or K-tail—is an automotive styling feature wherein the rear of the car slopes downwards before being abruptly cut off with a vertical or near-vertical surface. A Kammback improves aerodynamic drag, thus improving efficiency and fuel consumption, while maintaining a practical shape for a vehicle. The Kammback is named after German aerodynamicist Wunibald Kamm for his work developing the design in the 1930s. Some vehicles incorporate the kammback design based on aerodynamic principles, while some use a cut-off tail as a design or marketing feature. Origins As the speed of cars increased during the 1920s and 1930s, designers observed and began to apply the principles of automotive aerodynamics. As aerodynamic drag increases, more energy, and thus more fuel, are required to advance a vehicle. In 1922, Paul Jaray patented a car based on a teardrop profile (i.e. with a rounded nose and long, tapered tail) to minimize the aerodynamic drag that is created at higher speeds. The streamliner vehicles of the mid 1930s—such as the Tatra 77, Chrysler Airflow and Lincoln-Zephyr—were designed according to these discoveries. However, the long tail was not a practical shape for a car, so automotive designers sought other solutions. In 1935, German aircraft designer Georg Hans Madelung showed alternatives to minimize drag without a long tail. In 1936, a similar theory was applied to cars after Baron Reinhard Koenig-Fachsenfeld developed a smooth roofline shape with an abrupt end at a vertical surface, effective in achieving low amounts of drag similar to a streamlined body. He worked on an aerodynamic design for a bus, and Koenig-Fachsenfeld patented the idea. Koenig-Fachsenfeld worked with Wunibald Kamm at Stuttgart University, investigating vehicle shapes to "provide a good compromise between everyday utility (e.g. vehicle length and interior dimensions) and an attractive drag coefficient". In addition to aerodynamic efficiency, Kamm emphasized vehicle stability in his design, mathematically and empirically proving the effectiveness of the design. In 1938, Kamm produced a prototype using a Kammback shape, based on a BMW 328. The Kammback, along with other aerodynamic modifications, gave the prototype a drag coefficient of 0.25. The earliest mass-produced cars using Kammback principles were the 1949–1951 Nash Airflyte in the United States and the 1952–1955 Borgward Hansa 2400 in Europe. Aerodynamic theory The ideal shape to minimize drag is a "teardrop," a smooth airfoil-like shape, but it is not practical for road vehicles because of size