A glider or sailplane is a type of glider aircraft used in the leisure activity and sport of gliding. This unpowered aircraft can use occurring currents of rising air in the atmosphere to gain altitude. Sailplanes are aerodynamically streamlined and so can fly a significant distance forward for a small decrease in altitude. In North America the term'sailplane' is used to describe this type of aircraft. In other parts of the English-speaking world, the word'glider' is more common. Sailplanes benefit from producing the least drag for any given amount of lift, this is best achieved with long, thin wings, a faired narrow cockpit and a slender fuselage. Aircraft with these features are able to soar - climb efficiently in rising air produced by thermals or hills. In still air, sailplanes can glide long distances at high speed with a minimum loss of height in between. Sailplanes have either skids or undercarriage. In contrast hang gliders and paragliders use the pilot's feet for the start of the launch and for the landing.
These latter types are described in separate articles, though their differences from sailplanes are covered below. Sailplanes are launched by winch or aerotow, though other methods, auto tow and bungee, are used; these days all gliders are sailplanes, but in the past many gliders were not. These types did not soar, they were engine-less aircraft towed by another aircraft to a desired destination and cast off for landing. The prime example of non-soaring gliders were military gliders (such as those used in the Second World War, they were used just once and usually abandoned after landing, having served their purpose. Motor gliders are gliders with engines which can be used for extending a flight and in some cases, for take-off; some high-performance motor gliders may have an engine-driven retractable propeller which can be used to sustain flight. Other motor gliders have enough thrust to launch themselves before the engine is retracted and are known as "self-launching" gliders. Another type is the self-launching "touring motor glider", where the pilot can switch the engine on and off in flight without retracting the propeller.
Sir George Cayley's gliders achieved brief wing-borne hops from around 1849. In the 1890s, Otto Lilienthal built gliders using weight shift for control. In the early 1900s, the Wright Brothers built gliders using movable surfaces for control. In 1903, they added an engine. After World War I gliders were first built for sporting purposes in Germany. Germany's strong links to gliding were to a large degree due to post-WWI regulations forbidding the construction and flight of motorised planes in Germany, so the country's aircraft enthusiasts turned to gliders and were encouraged by the German government at flying sites suited to gliding flight like the Wasserkuppe; the sporting use of gliders evolved in the 1930s and is now their main application. As their performance improved, gliders began to be used for cross-country flying and now fly hundreds or thousands of kilometres in a day if the weather is suitable. Early gliders had the pilot sat on a small seat located just ahead of the wing; these were known as "primary gliders" and they were launched from the tops of hills, though they are capable of short hops across the ground while being towed behind a vehicle.
To enable gliders to soar more than primary gliders, the designs minimized drag. Gliders now have smooth, narrow fuselages and long, narrow wings with a high aspect ratio and winglets; the early gliders were made of wood with metal fastenings and control cables. Fuselages made of fabric-covered steel tube were married to wood and fabric wings for lightness and strength. New materials such as carbon-fiber, fiber glass and Kevlar have since been used with computer-aided design to increase performance; the first glider to use glass-fiber extensively was the Akaflieg Stuttgart FS-24 Phönix which first flew in 1957. This material is still used because of its high strength to weight ratio and its ability to give a smooth exterior finish to reduce drag. Drag has been minimized by more aerodynamic shapes and retractable undercarriages. Flaps are fitted to the trailing edges of the wings on some gliders to optimise lift and drag at a wide range of speeds. With each generation of materials and with the improvements in aerodynamics, the performance of gliders has increased.
One measure of performance is the glide ratio. A ratio of 30:1 means that in smooth air a glider can travel forward 30 meters while losing only 1 meter of altitude. Comparing some typical gliders that might be found in the fleet of a gliding club – the Grunau Baby from the 1930s had a glide ratio of just 17:1, the glass-fiber Libelle of the 1960s increased that to 39:1, modern flapped 18 meter gliders such as the ASG29 have a glide ratio of over 50:1; the largest open-class glider, the eta, has a span of 30.9 meters and has a glide ratio over 70:1. Compare this to the Gimli Glider, a Boeing 767 which ran out of fuel mid-flight and was found to have a glide ratio of 12:1, or to the Space Shuttle with a glide ratio of 4.5:1. High aerodynamic efficiency is essential to achieve a good gliding performance, so gliders have aerodynamic features found in other aircraft; the wings of a modern racing glider are designed by computers to create a low-drag laminar flow airfoil. After the wings' surfaces have been shaped by a mould to great accuracy, they are highly polished.
Vertical winglets at the ends of the wings decrease drag and so improve wing efficiency. Special aerodynamic seals are used at the ailerons and elevator to
Petar Krpan is a Croatian retired footballer who played as a forward. Born in Osijek, Socialist Federal Republic of Yugoslavia, Krpan started his career with local club NK Osijek. Due to the war breaking out in 1991, as a 17-year-old he engaged in battle to help save his hometown, he moved to Sporting Clube de Portugal in 1998, being scarcely used during his one-and-a-half-season spell. In January 2000, staying in Portugal, Krpan left for U. D. Leiria and played for the team until the summer of 2001 on loan, he returned to Croatia and played one season apiece for Osijek, NK Zagreb and HNK Hajduk Split, before returning to Leiria for 2004–05. In 2005, Krpan once again moved back to his country by joining HNK Rijeka, where he spent one season before moving to second division side NK Inter Zaprešić. Krpan won three caps for the Croatia national team in 1998, all as a second-half substitute, his debut occurred on 6 June in a friendly match in Zagreb. Krpan was a member of the bronze medal-winning squad at the 1998 FIFA World Cup where he made one appearance, playing the last 13 minutes of the round-of-16 match against Romania.
NK ZagrebCroatian First League: 2001–02Hajduk SplitCroatian First League: 2003–04 Croatian Football Cup: 2002–03RijekaCroatian Football Cup: 2005–06Inter ZaprešićCroatian Second League: 2006–07 Franjo Bučar State Award for Sport: 1998 Order of the Croatian Interlace – 1998 Petar Krpan at ForaDeJogo Petar Krpan at the Croatian Football Federation Petar Krpan at National-Football-Teams.com Petar Krpan – FIFA competition record
Sisu K-50SS is a six-wheel-driven ballast tractor made by the Finnish heavy vehicle producer Suomen Autoteollisuus. The vehicle can generate a 388 kN drawing force and it was used for pulling flatbed trailers. Only one unit was produced in 1961 and it is the largest roadworthy motor vehicle built in the Nordic countries. K-50SS was developed under assignment of Kemijoki Oy, which ordered at the end of 1959 two 6×6-driven heavy haulers for moving over 1 000 tonnes weighing transformers and other heavy components on flatbed trailers; the initial idea was having two units, of which one would have been used for trailer pulling meanwhile the other one would have pushed the trailer from behind. The vehicles were planned to be used separately serving on power plant construction sites all over Finland. SAT had produced six heavy Sisu K-36 earthmovers and the knowhow was utilised in the engineering work; the first unit was ready in spring 1961, just 1.5 year after the assignment. However, Kemijoki cancelled the order of the produced vehicle remained unique.
The vehicle is powered by Rolls-Royce C6TFL turbocharged 6-cylinder in-line, four-stroke diesel engine. Its 223-kW output is 43% and 1 070 Nm torque 56% higher compared to the standard aspirated type; the cylinder bore is 130.2 mm and stroke 152.2 mm. The compression ratio is 14:1; the engine is fitted with an air-start system. The hydraulic Rolls-Royce BF 11500Ms230 torque multiplier has three steps; the three-step main gearbox is made by Foden. The power is divided between the front axle and two rear axles by a differential inside the ZF VG-800-4V1 transfer case; the mechanism includes disengaging possibility of the front-wheel-drive for transition drive. The maximum ratio passes nearly 65 000 Newton circumferential force on each wheel; the Kirkstall-made driven axles are equipped with interlockable differentials. The torque between the rear axles is divided by a longitudinal differential; the chassis is constructed in a similar manner as in locomotives. The large cabin is fitted with a small kitchen.
The K-50SS was used for heavy hauling in North Finnish hydroelectric power plant construction sites. The 19 300 kg weighing vehicle could be further loaded by extra concrete weights up to 52 000 kg total weight in order to improve the tyre grip; the hydraulic torque multiplier enables passing torque to the wheels when the vehicle is standing still, enabling a smooth start. The maximum speed with the highest ratio is 10 km/h; the hydraulic clutch can be used for decelerating. According to the contemporary drivers and other people who were involved, the vehicle is easy to drive and it has always fulfilled the expectations given to it; the vehicle cost 21 million marks in the early 1960s and it has only run 43 000 km till 2010. The K-50SS is the all-time largest individual roadworthy automobile unit produced in the Nordic countries, without a tipper or other superstructures. Larger vehicles have been built but not homologated to be used on public roads; when coming to 21st century, the K-50SS was not in active use any more but stored in a garage at Pirttikoski power plant.
It was restored to its original outfit little by little and presented in various vintage vehicle meetings, until Kemijoki Oy gave the Sisu to Oulu Automobile Museum in 2006. Blomberg, Olli. Suomalaista Sisua vuodesta 1931 – Monialaosaajasta kuorma-autotehtaaksi. Karis: Oy Sisu Auto Ab. ISBN 952-91-4918-2. Side view on Sisu K-50SS