Rules to play Hang Gliding
1. Hang glider sailcloth
There are basically two types of sail materials used in hang glider sails Woven Polyester Fabrics, and Composite Laminated Fabrics made of some combination of polyester film and polyester fibers.Woven polyester sailcloth is a very tight weave of small diameter polyester fibers that has been stabilized by the hot press impregnation of a polyester resin. The resin impregnation is required to provide resistance to distortion and stretch. This resistance is important in maintaining the aerodynamic shape of the sail. Woven polyester provides the best combination of light weight and durability in a sail with the best overall handling qualities.
Laminated sail materials using polyester film achieve superior performance by using a lower stretch material that is better at maintaining sail shape but is still relatively light in weight. The disadvantages of polyester film fabrics is that the reduced elasticity under load generally results in stiffer and less responsive handling, and polyester laminated fabrics are generally not as durable or long lasting as the woven fabrics.
2. Triangle control frame
In most hang gliders, the control is and has been achieved using a horizontal bar held by the pilot, also known as triangle control frame (TCF), control bar or base bar. This bar is usually pulled to allow for greater speed. Either end of the control bar is attached to an upright, where both extend and are connected to the main body of the glider. This creates the shape of a triangle or A Frame. In many of these configurations additional wheels or other equipment can be suspended from the bottom bar or rod ends.
Images showing a triangle control frame on Otto Lilienthals 1892 hang glider prove that the technology of such frames has existed since the early design of gliders, but he did not mention it in his patents. A TCF shows also in Octave Chanutes designs. It was a major part of the now common design of hang gliders by George A. Spratt from 1929.The most simple A frame that is cable stayed was demonstrated in a Breslau gliding club hang gliding meet in a battened wing hang glider in the year 1908; hang glider historian Stephan Nitsch has collected instances also of the U control frame used in the first decade of the 1900s; the U is variant of the A frame.
3. Training and safety
Due to the poor safety record of early hang gliding pioneers, the sport has traditionally been considered unsafe. Advances in pilot training and glider construction have led to a much improved safety record. Modern hang gliders are very sturdy when constructed to HGMA[expand acronym], BHPA, DHV[expand acronym], or other certified standards using modern materials. Although lightweight they can be easily damaged, either through misuse or by continued operation in unsafe wind and weather conditions. All modern gliders have built in dive recovery mechanisms such as luff lines in kingposted gliders, or sprogs in topless gliders.
Pilots fly in a harness which supports their body. Several different types of harnesses exist. Pod harnesses are put on like a jacket and the leg portion is behind the pilot during launch. Once in the air the feet are tucked into the bottom of the harness. They are zipped up in the air with a rope and unzipped before landing with a separate rope. A cocoon harness is slipped over the head and lies in front of the legs during launch. After getting into the air the feet are tucked into it and the back is left open. A knee hanger harness is also slipped over the head but the knee part is wrapped around the knees before launch and just pick up the pilots leg automatically after launch. A supine or suprone harness is a seated harness. The shoulder straps are put on before launch and after take off the pilot slides back into the seat and flies in a seated position.
Pilots carry a parachute enclosed in the harness. In case of serious problems the parachute is manually deployed and carries both pilot and glider down to earth. Pilots also wear helmets and generally carry other safety items such as knives (for cutting their parachute bridle after impact or cutting their harness lines and straps in case of a tree or water landing), light ropes (for lowering from trees to haul up tools or climbing ropes), radios (for communication with other pilots or ground crew), and first aid equipment.
The accident rate from hang glider flying has been dramatically decreased by pilot training. Early hang glider pilots learned their sport through trial and error and gliders were sometimes home built. Training programs have been developed for todays pilot with emphasis on flight within safe limits, as well as the discipline to cease flying when weather conditions are unfavorable, for example excess wind or risk cloud suck.In the UK there is one death per 116,000 flights, a risk comparable to running a marathon or playing football for a year.
Launch techniques include foot launching from a hill, tow launching from a ground based tow system, aerotowing (behind a powered aircraft), powered harnesses, and being towed up by a boat. Modern winch tows typically utilize hydraulic systems designed to regulate line tension, this reduces scenarios for lock out as strong winds result in additional length of rope spooling out rather than direct tension on the tow line. Other more exotic launch techniques have also been used successfully, such as hot air balloon drops from very high altitude. When weather conditions are unsuitable to sustain a soaring flight, results in a top to bottom fight and referred to as sled runs.
5. Soaring flight and cross
A glider in flight is continuously descending. To achieve an extended flight, the pilot must seek air currents rising faster than the sink rate of the glider. Selecting the sources of rising air currents is the skill that has to be mastered if the pilot wants to achieve flying long distances, known as cross country (XC). Rising air masses derive from the following sources.
The most commonly used source of lift is created by the suns energy heating the ground which in turn heats the air above it. This warm air rises in columns known as thermals. Soaring pilots quickly become aware of land features which can generate thermals and their trigger points downwind, because thermals have a surface tension with the ground and roll until hitting a trigger point. When the thermal lifts, the first indicator are the swooping birds feeding on the insects being carried aloft, or dust devils or a change in wind direction as the air is pulled in below the thermal. As the thermal climbs, bigger soaring birds indicate the thermal. The thermal rises until it either forms into a cumulus cloud or hits an inversion layer, which is where the surrounding air is becoming warmer with height, and stops the thermal developing into a cloud. Also, nearly every glider contains an instrument known as a variometer (a very sensitive vertical speed indicator) which shows visually (and often audibly) the presence of lift and sink. Having located a thermal, a glider pilot will circle within the area of rising air to gain height. In the case of a cloud street, thermals can line up with the wind, creating rows of thermals and sinking air. A pilot can use a cloud street to fly long straight line distances by remaining in the row of rising air.
7. Ridge lift
Ridge lift occurs when the wind encounters a mountain, cliff or hill. The air is pushed up the windward face of the mountain, creating lift. The area of lift extending from the ridge is called the lift band. Providing the air is rising faster than the gliders sink rate, gliders can soar and climb in the rising air by flying within the lift band and at right angle to the ridge. Ridge soaring is also known as slope soaring.
8. Mountain waves
The third main type of lift used by glider pilots is the lee waves that occur near mountains. The obstruction to the airflow can generate standing waves with alternating areas of lift and sink. The top of each wave peak is often marked by lenticular cloud formations.
Another form of lift results from the convergence of air masses, as with a sea breeze front. More exotic forms of lift are the polar vortices which the Perlan Project hopes to use to soar to great altitudes. A rare phenomenon known as Morning Glory has also been used by glider pilots in Australia.
With each generation of materials and with the improvements in aerodynamics, the performance of hang gliders has increased. One measure of performance is the glide ratio. For example, a ratio of 121 means that in smooth air a glider can travel forward 12 metres while only losing 1 metre of altitude.Some performance figures as of 2006 Topless gliders (no kingpost) glide ratio ~171, speed range ~30 to >145 km h, best glide at 45 to 60 km h Rigid wings glide ratio ~201, speed range ~ 35 to > 130 km h, best glide at ~50 to 60 km h.
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