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The Rogallo wing is a flexible type of wing. In 1948, Francis Rogallo, a NASA engineer, and his wife Gertrude Rogallo, invented a self-inflating flexible wing they called the Parawing, also known after them as the "Rogallo Wing" and flexible wing. NASA considered Rogallo's flexible wing as an alternative recovery system for the Project Mercury and Project Gemini , and for possible use in other spacecraft landings, but the idea was dropped from Gemini in 1964 in favor of conventional parachutes.
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 (empennage).
Single-point hang was fully demonstrated in Breslau in 1908, as well as the triangle control frame that would later be seen in NASA's and John Worth's hang gliders and powered hang gliders. Thomas Purcell and Mike Burns would use the triangle control frame. Much later Dickenson would do similarly as he fashioned an airframe to fit on the by-then standard four boom stiffened Rogallo wing.Article by Mark Woodhams, British Columbia Hang Gliding and Paragliding Association: Western Museum of Flight Dickenson's model made use of a single hang point and an A frame: Innovation in education – John Dickenson The Australian Ultralight Federation -History 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 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. 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) left or right or forward or aft. Several control methods were studied by NASA for Rogallo wings from 1958 through the 1960s embodied in different versions of the Parawing.
On Rogallo wing hang gliders, John 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.
The Delta II had colored suspension lines to help guide the packing process, and also had a unique "Opening Shock Inhibitor" OSI strap that helped retard the high opening speeds and shocks. The packing volume of the canopy was slightly bigger than the then state-of-the-art Para-Commander. As one of the first types of gliding canopy, it received a considerable level of interest from jumpers. However, it developed a reputation for being unreliable, as it seemed prone to malfunctions on opening, possibly due to the unorthodox packing techniques for such a new design of canopy. However, when deployed successfully, the glide and performance was markedly better than a Para-Commander type canopy.
The Delta II was available until 1975 and paved the way for other Rogallo Wing skydiving canopies, such as the Handbury Para-Dactyl. This was made in both single-keel and dual-keel versions as a main parachute in the mid to late 1970s, and also as a reserve parachute version known as a Safety-Dactyl. This was a US-made canopy and featured a sail-slider to reduce opening speeds and opening forces as is normal on a modern ram air canopy. A Russian Rogallo-Wing canopy known as a PZ-81 was available as late as 1995. The Rogallo wing canopy was superseded in the late 1970s by the ram-air canopies which had improved their reliability and performance, and reduced their packed volume, compared to all other gliding and non-gliding parachutes.
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.
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