The Rogallo wing is a flexible type of airfoil. In 1948, Gertrude Rogallo, and her husband Francis Rogallo, a NASA engineer, invented a self-inflating flexible wing they called the Parawing, also known after them as the "Rogallo Wing" and flexible wing.[1] NASA considered Rogallo's flexible wing as an alternative recovery system for the Gemini space capsule and for possible use in other spacecraft landings, but the idea was dropped in 1964 in favor of parachutes.
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Rogallo had been interested in the flexible wing since 1945. He and his wife built and flew kites as a hobby and, since they could not find official backing for the wing (including at Rogallo's employer NACA), carried out experiments in their own time. By the end of 1948 they had two working designs using a flexible wing - a kite (which they called "Flexi-Kite") and a gliding parachute (which they later referred to as a "paraglider").[2] Rogallo and his wife received a patent on a "V-shaped" flexible wing in March 1951. Selling the Flexi-kite as a toy helped to finance their work and publicize the design.
A Rogallo wing is composed of two partial conic surfaces with both cones pointing forward. Slow Rogallo wings have wide, shallow cones. Fast subsonic and supersonic Rogallo wings have long, narrow cones. The Rogallo wing is a simple and inexpensive flying wing with remarkable properties. The wing itself is not a kite; neither is it a glider nor a powered aircraft, until the wing is tethered or arranged in a configuration that glides or is powered. In other words, how it is attached and manipulated determines what type of aircraft it becomes. The Rogallo wing is most often seen in toy kites, but has been used to construct spacecraft parachutes, sport parachutes, ultralight powered aircraft like the trike and hang gliders. Rogallo had more than one patent concerning his finding; the due-diligence expansion of his invention involved cylindrical formats, multiple lobes, various stiffenings, various nose angles, etc. The Charles Richard design and use of the Rogallo wing in the Paresev project resulted in an assemblage that became the stark template for the standard Rogallo hang-glider wing that would blanket the world of the sport in the early 1970s.
Beyond that, the wing is designed to bend and flex in the wind, and so provides favorable dynamics analogous to a spring suspension. Flexibility allows the wing to be less susceptible to turbulence and provides a gentler flying experience than a similarly-sized rigid-winged aircraft. The trailing edge of the wing – which is not stiffened – allows the wing to twist, and provides aerodynamic stability without the need for a tail (empenage).
In 1961-1962 aeronautical engineer Barry Palmer foot-launched several versions of a framed Rogallo wing hang glider to continue the recreational and sporting spirit of hang gliding. Another player in the continuing evolution of the Rogallo wing hang glider was Australian John Dickenson, who in 1963 set to build a controllable water skiing kite/glider. Publicity from the Paresev tested and flown hang gliders sparked interest in the design among several tinkerers, including John Dickenson.[3]
Dickenson fashioned an airframe to fit on a Rogallo airfoil.[4][5] Dickenson's model made use of a single hang point and an A frame:[6][7] He started with a framed Rogallo wing airfoil with a U-frame (later an A-frame control bar) to it; it was composed of a keel, leading edges, a cross-bar and a fixed control frame. Weight-shift (mass-shift) was also used to control the glider. The flexible wing - called "Ski Wing" - was first flown in public at the Grafton Jacaranda Festival in September 1963 by Rod Fuller while towed behind a motorboat.
The 'Australian Self-Soar Association' states that the first foot-launch of a hang glider in Australia was in 1972[8] In Torrance, California, Bill Moyes was assisted in a kited foot-launch by Joe Faust at a beach slope in 1971 or 1972. Moyes went on to build a company with his own trade-named Rogallo wing hang gliders that used the trapeze control frame he had seen in Dickenson's and Australian manned flat-kite ski kites. Bill Moyes and Bill Bennett exported new refinements of their own hang gliders throughout the world.
The parawing hang glider was inducted into the Space Foundation Space Technology Hall of Fame in 1995.
Hang gliders have been used with different forms of weight-shift control since Otto Lilienthal. The most common way to shift the center of gravity was to fly while suspended from the underarms by two parallel bars. Gottlob Espenlaub (1922), George Spratt (1929) and Barry Palmer (1962) used pendulum seats for the pilot. Interaction with the frame provided various means of control of the Rogallo winged hang glider.
Today, most Rogallo wings are also controlled by changing their pitch and roll by means of shifting its center of gravity. This is done by suspending the payload from one or more points beneath the wing and then moving the pendulumed mass of the payload (pilot and things else) mass left or right or forward or aft. Several control methods were studied in NASA for Rogallo wings from 1958 through the 1960s embodied in different versions of the Parawing.
On Rogallo wing hang gliders, John W. Dickenson used a type of weight-shift control frame composed of a mounted triangular control frame under the wing. The pilot sat on a seat and was sometimes also harnessed about the torso. The pilot was suspended behind the triangular control frame which was used as a hand support to push and pull in order to shift the pilot's weight relative to the mass and attitude of the wing above.
Rogallo wing kites control pitch with a bridle that sets the wing's angle of attack. A bridle made of string is usually a loop reaching from the front to the end of the center strut of the A-frame. The user ties knots (usually a girth hitch) in the bridle to set the angle of attack. Mass-produced rogallo kites use a bridle that's a triangle of plastic film, with one edge heat-sealed to the central strut.
Steerable Rogallo kites usually have a pair of bridles setting a fixed pitch, and use two strings, one on each side of the kite, to change the roll.
Rogallo also developed a series of soft foil designs in the 1960s which have been modified for traction kiting. These are double keel designs with conic wings and a multiple attachment bridle which can be used with either dual line or quad line controls. They have excellent pull, but suffer from a smaller window than more modern traction designs. Normally the #5 and #9 alternatives are used.