Misplaced Pages

#353646

90-697: A boomerang ( / ˈ b uː m ə r æ ŋ / ) is a thrown tool typically constructed with airfoil sections and designed to spin about an axis perpendicular to the direction of its flight. A returning boomerang is designed to return to the thrower, while a non-returning boomerang is designed as a weapon to be thrown straight and is traditionally used by some Aboriginal Australians for hunting. Historically, boomerangs have been used for hunting , sport, and entertainment and are made in various shapes and sizes to suit different purposes. Although considered an Australian icon, ancient boomerangs have also been discovered in Egypt,

180-605: A spear -thrower. An anonymous 1790 manuscript on Aboriginal languages of New South Wales reported "Boo-mer-rit" as "the Scimiter". In 1822, it was described in detail and recorded as a "bou-mar-rang" in the language of the Turuwal people (a sub-group of the Darug ) of the Georges River near Port Jackson. The Turawal used other words for their hunting sticks but used "boomerang" to refer to

270-430: A 'boom' or 'rang') is made of Finnish birch plywood , hardwood , plastic or composite materials and comes in many different shapes and colours. Most sport boomerangs typically weigh less than 100 g (3.5 oz), with MTA boomerangs (boomerangs used for the maximum-time-aloft event) often under 25 g (0.88 oz). Boomerangs have also been suggested as an alternative to clay pigeons in shotgun sports, where

360-408: A 250–300 mm (9.8–11.8 in) wingspan, and a 20–40 m (66–131 ft) range. A falling boomerang starts spinning, and most then fall in a spiral. When the boomerang is thrown with high spin, a boomerang flies in a curved rather than a straight line. When thrown correctly, a boomerang returns to its starting point. As the wing rotates and the boomerang moves through the air, the airflow over

450-512: A boomerang by Europeans was at Farm Cove ( Port Jackson ), in December 1804, when a weapon was witnessed during a tribal skirmish : ... the white spectators were justly astonished at the dexterity and incredible force with which a bent, edged waddy resembling slightly a Turkish scimytar , was thrown by Bungary , a native distinguished by his remarkable courtesy. The weapon, thrown at 20 or 30 yards [18 or 27 m] distance, twirled round in

540-629: A general purpose airfoil that finds wide application, and pre–dates the NACA system, is the Clark-Y . Today, airfoils can be designed for specific functions by the use of computer programs. The various terms related to airfoils are defined below: The geometry of the airfoil is described with a variety of terms : The shape of the airfoil is defined using the following geometrical parameters: Some important parameters to describe an airfoil's shape are its camber and its thickness . For example, an airfoil of

630-475: A hawk, the ducks would dive away, toward hunters armed with nets or clubs. Traditionally, most boomerangs used by Aboriginal groups in Australia were non-returning. These weapons, sometimes called "throwsticks" or "kylies", were used for hunting a variety of prey, from kangaroos to parrots; at a range of about 100 m (330 ft), a 2 kg (4.4 lb) non-returning boomerang could inflict mortal injury to

720-929: A large animal. A throwstick thrown nearly horizontally may fly in a nearly straight path and could fell a kangaroo on impact to the legs or knees, while the long-necked emu could be killed by a blow to the neck. Hooked non-returning boomerangs, known as "beaked kylies", used in northern Central Australia, have been claimed to kill multiple birds when thrown into a dense flock. Throwsticks are used as multi-purpose tools by today's Aboriginal peoples, and besides throwing could be wielded as clubs, used for digging, used to start friction fires, and are sonorous when two are struck together. Recent evidence also suggests that boomerangs were used as war weapons. Today, boomerangs are mostly used for recreation. There are different types of throwing contests: accuracy of return; Aussie round; trick catch; maximum time aloft ; fast catch; and endurance (see below). The modern sport boomerang (often referred to as

810-628: A population of 155,000. The city of Sorong has a population of 125,000 and, within the metropolitan area, a population of 170,000. This city also has the largest metropolitan area. Papuan Malay is the local lingua franca spoken in the Bird's Head Peninsula. The official language is Indonesian . The Austronesian languages spoken on the Bird's Head Peninsula mostly belong to the South Halmahera–West New Guinea (SHWNG) group. There are various non-Austronesian Papuan languages native to

900-476: A returning throw-stick . Boomerangs were, historically, used as hunting weapons, percussive musical instruments , battle clubs , fire-starters, decoys for hunting waterfowl , and as recreational play toys. The smallest boomerang may be less than 10 cm (3.9 in) from tip to tip, and the largest over 180 cm (71 in) in length. Tribal boomerangs may be inscribed or painted with designs meaningful to their makers. Most boomerangs seen today are of

990-401: A returning one. The curving flight characteristic of returning boomerangs was probably first noticed by early hunters trying to "tune" their throwing sticks to fly straight. It is thought by some that the shape and elliptical flight path of the returning boomerang makes it useful for hunting birds and small animals, or that noise generated by the movement of the boomerang through the air, or, by

SECTION 10

#1732845492354

1080-437: A sharp leading edge. All have a sharp trailing edge . The air deflected by an airfoil causes it to generate a lower-pressure "shadow" above and behind itself. This pressure difference is accompanied by a velocity difference, via Bernoulli's principle , so the resulting flowfield about the airfoil has a higher average velocity on the upper surface than on the lower surface. In some situations (e.g., inviscid potential flow )

1170-413: A skilled thrower, lightly clipping leaves of a tree whose branches house birds, would help scare the birds towards the thrower. It is further supposed by some that this was used to frighten flocks or groups of birds into nets that were usually strung up between trees or thrown by hidden hunters. In southeastern Australia, it is claimed that boomerangs were made to hover over a flock of ducks; mistaking it for

1260-421: A subsonic flow about a thin airfoil can be described in terms of an outer region, around most of the airfoil chord, and an inner region, around the nose, that asymptotically match each other. As the flow in the outer region is dominated by classical thin airfoil theory, Morris's equations exhibit many components of thin airfoil theory. In thin airfoil theory, the width of the (2D) airfoil is assumed negligible, and

1350-429: A suitable angle, a solid body moving through a fluid deflects the oncoming fluid (for fixed-wing aircraft, a downward force), resulting in a force on the airfoil in the direction opposite to the deflection. This force is known as aerodynamic force and can be resolved into two components: lift ( perpendicular to the remote freestream velocity ) and drag ( parallel to the freestream velocity). The lift on an airfoil

1440-404: A very narrow throwing window, which discourages many beginners from continuing with this discipline. For the same reason, the quality of manufactured long-distance boomerangs is often difficult to determine. Today's long-distance boomerangs have almost all an S or ? – question mark shape and have a beveled edge on both sides (the bevel on the bottom side is sometimes called an undercut). This

1530-560: A word meaning "boomerang" taken from one of the Western Desert languages, for example, the Warlpiri word "karli". Trademarks of Australian companies using the boomerang as a symbol, emblem or logo proliferate, usually removed from Aboriginal context and symbolising "returning" or to distinguish an Australian brand. Early examples included Bain's White Ant Exterminator (1896); Webendorfer Bros. explosives (1898); E. A. Adams Foods (1920); and by

1620-579: Is evidence of the use of non-returning boomerangs by the Native Americans of California and Arizona , and inhabitants of South India for killing birds and rabbits. Some boomerangs were not thrown at all, but were used in hand to hand combat by Indigenous Australians . Ancient Egyptian examples, however, have been recovered, and experiments have shown that they functioned as returning boomerangs. Hunting sticks discovered in Europe seem to have formed part of

1710-401: Is increased before the wing achieves maximum thickness to minimize the chance of boundary layer separation. This elongates the wing and moves the point of maximum thickness back from the leading edge. Supersonic airfoils are much more angular in shape and can have a very sharp leading edge, which is very sensitive to angle of attack. A supercritical airfoil has its maximum thickness close to

1800-454: Is not true for other types of boomerangs, where the loss of kinetic energy is non-reversible (the MTAs also store kinetic energy in potential energy during the first half of the flight, but then the potential energy is lost directly by the drag). In Noongar language , kylie is a flat curved piece of wood similar in appearance to a boomerang that is thrown when hunting for birds and animals. "Kylie"

1890-594: Is often referred to as The Vogelkop, and is so named because its shape looks like a bird's head on the island of New Guinea. The peninsula at the opposite end of the island (in Papua New Guinea ) is called the Bird's Tail Peninsula . The peninsula just to the south is called the Bomberai Peninsula . The Bird's Head Peninsula is at the northwestern end of the island of New Guinea . It is bounded by Cenderawasih Bay to

SECTION 20

#1732845492354

1980-454: Is one of the Aboriginal words for the hunting stick used in warfare and for hunting animals. Instead of following curved flight paths, kylies fly in straight lines from the throwers. They are typically much larger than boomerangs, and can travel very long distances; due to their size and hook shapes, they can cripple or kill an animal or human opponent. The word is perhaps an English corruption of

2070-421: Is preferable for an accurate throw, light winds up to 3–5 knots (6–9 km/h; 3–6 mph) are manageable with skill. If the wind is strong enough to fly a kite, then it may be too strong unless a skilled thrower is using a boomerang designed for stability in stronger winds. Gusty days are a great challenge, and the thrower must be keenly aware of the ebb and flow of the wind strength, finding appropriate lulls in

2160-406: Is primarily the result of its angle of attack . Most foil shapes require a positive angle of attack to generate lift, but cambered airfoils can generate lift at zero angle of attack. Airfoils can be designed for use at different speeds by modifying their geometry: those for subsonic flight generally have a rounded leading edge , while those designed for supersonic flight tend to be slimmer with

2250-401: Is the position at which the pitching moment M ′ does not vary with a change in lift coefficient: ∂ ( C M ′ ) ∂ ( C L ) = 0 . {\displaystyle {\frac {\partial (C_{M'})}{\partial (C_{L})}}=0{\text{.}}} Thin-airfoil theory shows that, in two-dimensional inviscid flow,

2340-420: Is to minimise drag and lower the lift. Lift must be low because the boomerang is thrown with an almost total layover (flat). Long-distance boomerangs are most frequently made of composite material, mainly fibre glass epoxy composites. The projection of the flight path of long-distance boomerang on the ground resembles a water drop . For older types of long-distance boomerangs (all types of so-called big hooks),

2430-434: Is usually flat. Boomerangs can be made for right- or left-handed throwers. The difference between right and left is subtle, the planform is the same but the leading edges of the aerofoil sections are reversed. A right-handed boomerang makes a counter-clockwise, circular flight to the left while a left-handed boomerang flies clockwise to the right. Most sport boomerangs weigh between 70 and 110 g (2.5 and 3.9 oz), have

2520-495: The Biot–Savart law , the vorticity γ( x ) produces a flow field w ( x ) = 1 2 π ∫ 0 c γ ( x ′ ) x − x ′ d x ′ , {\displaystyle w(x)={\frac {1}{2\pi }}\int _{0}^{c}{\frac {\gamma (x')}{x-x'}}\,dx'{\text{,}}} oriented normal to

2610-606: The Last Glacial Maximum , when lower sea levels led to cultural continuity between Papua and Arnhem Land in Northern Australia. The oldest surviving Australian Aboriginal boomerangs come from a cache found in a peat bog in the Wyrie Swamp of South Australia and date to 10,000 BC . Although traditionally thought of as Australian, boomerangs have been found also in ancient Europe, Egypt, and North America. There

2700-739: The Stone Age arsenal of weapons. One boomerang that was discovered in Obłazowa Cave in the Carpathian Mountains in Poland was made of mammoth's tusk and is believed, based on AMS dating of objects found with it, to be about 30,000 years old. In the Netherlands , boomerangs have been found in Vlaardingen and Velsen from the first century BC. King Tutankhamun owned a collection of boomerangs of both

2790-585: The Vogelkop montane rain forests ecoregion. The montane rain forests include an area of more than 22,000 km . Over 50% of the montane forests are located within protected areas. There are over 300 bird species on the peninsula, of which at least 20 are unique to the ecoregion, and some live only in very restricted areas. These include the grey-banded munia , Vogelkop bowerbird , and the king bird-of-paradise . Road construction, illegal logging , commercial agricultural expansion and ranching potentially threaten

Boomerang - Misplaced Pages Continue

2880-1287: The change of variables x = c ⋅ 1 + cos ⁡ ( θ ) 2 , {\displaystyle x=c\cdot {\frac {1+\cos(\theta )}{2}},} and then expanding both dy ⁄ dx and γ( x ) as a nondimensionalized Fourier series in θ with a modified lead term: d y d x = A 0 + A 1 cos ⁡ ( θ ) + A 2 cos ⁡ ( 2 θ ) + … γ ( x ) = 2 ( α + A 0 ) ( sin ⁡ θ 1 + cos ⁡ θ ) + 2 A 1 sin ⁡ ( θ ) + 2 A 2 sin ⁡ ( 2 θ ) + … . {\displaystyle {\begin{aligned}&{\frac {dy}{dx}}=A_{0}+A_{1}\cos(\theta )+A_{2}\cos(2\theta )+\dots \\&\gamma (x)=2(\alpha +A_{0})\left({\frac {\sin \theta }{1+\cos \theta }}\right)+2A_{1}\sin(\theta )+2A_{2}\sin(2\theta )+\dots {\text{.}}\end{aligned}}} The resulting lift and moment depend on only

2970-648: The convolution equation ( α − d y d x ) V = − w ( x ) = − 1 2 π ∫ 0 c γ ( x ′ ) x − x ′ d x ′ , {\displaystyle \left(\alpha -{\frac {dy}{dx}}\right)V=-w(x)=-{\frac {1}{2\pi }}\int _{0}^{c}{\frac {\gamma (x')}{x-x'}}\,dx'{\text{,}}} which uniquely determines it in terms of known quantities. An explicit solution can be obtained through first

3060-411: The trailing edge angle . The slope is greatest if the angle is zero; and decreases as the angle increases. For a wing of finite span, the aspect ratio of the wing also significantly influences the slope of the curve. As aspect ratio decreases, the slope also decreases. Thin airfoil theory is a simple theory of airfoils that relates angle of attack to lift for incompressible, inviscid flows . It

3150-496: The (still current) Boomerang Cigarette Papers Pty. Ltd. "Aboriginalia", including the boomerang, as symbols of Australia dates from the late 1940s and early 1950s and was in widespread use by a largely European arts, crafts and design community. By the 1960s, the Australian tourism industry extended it to the very branding of Australia, particularly to overseas and domestic tourists as souvenirs and gifts and thus Aboriginal culture. At

3240-663: The 1/4 chord point will thus be C M ( 1 / 4 c ) = − π / 4 ( A 1 − A 2 ) . {\displaystyle C_{M}(1/4c)=-\pi /4(A_{1}-A_{2}){\text{.}}} From this it follows that the center of pressure is aft of the 'quarter-chord' point 0.25 c , by Δ x / c = π / 4 ( ( A 1 − A 2 ) / C L ) . {\displaystyle \Delta x/c=\pi /4((A_{1}-A_{2})/C_{L}){\text{.}}} The aerodynamic center

3330-463: The 1980s revealed the practicality and usefulness of laminar flow wing designs and opened the way for laminar-flow applications on modern practical aircraft surfaces, from subsonic general aviation aircraft to transonic large transport aircraft, to supersonic designs. Schemes have been devised to define airfoils – an example is the NACA system . Various airfoil generation systems are also used. An example of

3420-400: The 21st century, souvenir objects depicting Aboriginal peoples, symbolism and motifs including the boomerang, from the 1940s–1970s, regarded as kitsch and sold largely to tourists in the first instance, became highly sought after by both Aboriginal and non-Aboriginal collectors and has captured the imagination of Aboriginal artists and cultural commentators. Airfoil When oriented at

3510-500: The Americas, and Eurasia. A boomerang is a throwing stick with aerodynamic properties, traditionally made of wood, but also of bone, horn, tusks and even iron. Modern boomerangs used for sport can be made from plywood or plastics such as ABS , polypropylene , phenolic paper , or carbon fibre-reinforced plastics . Boomerangs come in many shapes and sizes depending on their geographic or tribal origins and intended function, including

3600-409: The NACA 4-digit series such as the NACA 2415 (to be read as 2 – 4 – 15) describes an airfoil with a camber of 0.02 chord located at 0.40 chord, with 0.15 chord of maximum thickness. Finally, important concepts used to describe the airfoil's behaviour when moving through a fluid are: In two-dimensional flow around a uniform wing of infinite span, the slope of the lift curve is determined primarily by

3690-543: The aerodynamic center is at the quarter-chord position. Bird%27s Head Peninsula The Bird's Head Peninsula ( Indonesian : Kepala Burung , Dutch : Vogelkop , meaning Bird's Head in Indonesian and Dutch) or Doberai Peninsula ( Semenanjung Doberai ) is a large peninsula that makes up the northwest portion of the island of New Guinea , comprising the Indonesian provinces of Southwest Papua and West Papua . It

Boomerang - Misplaced Pages Continue

3780-408: The air and then crash. Fast Catch boomerangs usually have three or more symmetrical wings (seen from above), whereas a Long Distance boomerang is most often shaped similar to a question mark. Maximum Time Aloft boomerangs mostly have one wing considerably longer than the other. This feature, along with carefully executed bends and twists in the wings help to set up an "auto-rotation" effect to maximise

3870-402: The air with astonishing velocity, and alighting on the right arm of one of his opponents, actually rebounded to a distance not less than 70 or 80 yards [64 or 73 m], leaving a horrible contusion behind, and exciting universal admiration. David Collins listed "Wo-mur-rāng" as one of eight Aboriginal "Names of clubs" in 1798. but was probably referring to the woomera , which is actually

3960-428: The airfoil at x . Since the airfoil is an impermeable surface , the flow w ( x ) {\displaystyle w(x)} must balance an inverse flow from V . By the small-angle approximation , V is inclined at angle α- dy ⁄ dx relative to the blade at position x , and the normal component is correspondingly (α- dy ⁄ dx ) V . Thus, γ( x ) must satisfy

4050-466: The airfoil generates a circulation around the blade, which can be modeled as a vortex sheet of position-varying strength γ( x ) . The Kutta condition implies that γ( c )=0 , but the strength is singular at the bladefront, with γ( x )∝ 1 ⁄ √ x for x ≈ 0 . If the main flow V has density ρ , then the Kutta–Joukowski theorem gives that

4140-399: The airfoil itself replaced with a 1D blade along its camber line, oriented at the angle of attack α . Let the position along the blade be x , ranging from 0 at the wing's front to c at the trailing edge; the camber of the airfoil, dy ⁄ dx , is assumed sufficiently small that one need not distinguish between x and position relative to the fuselage. The flow across

4230-538: The boomerang go the furthest possible distance while returning close to the throwing point. In competition the boomerang must intersect an imaginary surface defined as an infinite vertical projection of a 40 m (130 ft) line centred on the thrower. Outside of competitions, the definition is not so strict, and throwers may be happy simply not to walk too far to recover the boomerang. Long-distance boomerangs are optimised to have minimal drag while still having enough lift to fly and return. For this reason, they have

4320-427: The boomerang to tilt around the axis of travel, because the boomerang has significant angular momentum, the gyroscopic precession causes the plane of rotation to tilt about an axis that is 90 degrees to the direction of flight, causing it to turn. When thrown in the horizontal plane, as with a Frisbee , instead of in the vertical, the same gyroscopic precession will cause the boomerang to fly violently, straight up into

4410-427: The boomerang's hover time in descending from the highest point in its flight. Some boomerangs have turbulators — bumps or pits on the top surface that act to increase the lift as boundary layer transition activators (to keep attached turbulent flow instead of laminar separation). Boomerangs are generally thrown in unobstructed, open spaces at least twice as large as the range of the boomerang. The flight direction to

4500-407: The chord line.) Also as a consequence of (3), the section lift coefficient of a cambered airfoil of infinite wingspan is: Thin airfoil theory assumes the air is an inviscid fluid so does not account for the stall of the airfoil, which usually occurs at an angle of attack between 10° and 15° for typical airfoils. In the mid-late 2000s, however, a theory predicting the onset of leading-edge stall

4590-403: The design of aircraft, propellers, rotor blades, wind turbines and other applications of aeronautical engineering. A lift and drag curve obtained in wind tunnel testing is shown on the right. The curve represents an airfoil with a positive camber so some lift is produced at zero angle of attack. With increased angle of attack, lift increases in a roughly linear relation, called the slope of

SECTION 50

#1732845492354

4680-503: The desired direction, with the right force. The boomerang is aimed to the right of the oncoming wind; the exact angle depends on the strength of the wind and the boomerang itself. Left-handed boomerangs are thrown to the left of the wind and will fly a clockwise flight path. The trajectory is either parallel to the ground or slightly upwards. The boomerang can return without the aid of any wind, but even very slight winds must be taken into account however calm they might seem. Little or no wind

4770-512: The east, Bintuni Bay to the south, and the Dampier Strait to the west. Across the strait is Waigeo , an island in the Raja Ampat archipelago. Batanta island lies just off the peninsula’s northwest tip. Another peninsula, Bomberai Peninsula , lies to the south, across Bintuni Bay. The peninsula is around 200 by 300 kilometers, and is bio-geographically diverse, containing coastal plains to

4860-435: The events listed below In all disciplines the boomerang must travel at least 20 metres (66 ft) from the thrower. Throwing takes place individually. The thrower stands at the centre of concentric rings marked on an open field. Events include: Non-discipline record : Smallest Returning Boomerang: Sadir Kattan of Australia in 1997 with 48 mm (1.9 in) long and 46 mm (1.8 in) wide. This tiny boomerang flew

4950-654: The experiment on board the International Space Station . Beginning in the later part of the twentieth century, there has been a bloom in the independent creation of unusually designed art boomerangs. These often have little or no resemblance to the traditional historical ones and on first sight some of these objects may not look like boomerangs at all. The use of modern thin plywoods and synthetic plastics have greatly contributed to their success. Designs are very diverse and can range from animal inspired forms, humorous themes, complex calligraphic and symbolic shapes, to

5040-409: The first and last third of the flight path are very low, while the middle third is a fast climb followed by a fast descent. Nowadays, boomerangs are made in a way that their whole flight path is almost planar with a constant climb during the first half of the trajectory and then a rather constant descent during the second half. From theoretical point of view, distance boomerangs are interesting also for

5130-598: The first few terms of this series. The lift coefficient satisfies C L = 2 π ( α + A 0 + A 1 2 ) = 2 π α + 2 ∫ 0 π d y d x ⋅ ( 1 + cos ⁡ θ ) d θ {\displaystyle C_{L}=2\pi \left(\alpha +A_{0}+{\frac {A_{1}}{2}}\right)=2\pi \alpha +2\int _{0}^{\pi }{{\frac {dy}{dx}}\cdot (1+\cos \theta )\,d\theta }} and

5220-762: The flight of the boomerang better mimics the flight of a bird offering a more challenging target. The modern boomerang is often computer-aided designed with precision airfoils. The number of "wings" is often more than 2 as more lift is provided by 3 or 4 wings than by 2. Among the latest inventions is a round-shaped boomerang, which has a different look but using the same returning principle as traditional boomerangs. This allows for safer catch for players. In 1992, German astronaut Ulf Merbold performed an experiment aboard Spacelab that established that boomerangs function in zero gravity as they do on Earth. French Astronaut Jean-François Clervoy aboard Mir repeated this in 1997. In 2008, Japanese astronaut Takao Doi again repeated

5310-405: The following important properties of airfoils in two-dimensional inviscid flow: As a consequence of (3), the section lift coefficient of a thin symmetric airfoil of infinite wingspan is: (The above expression is also applicable to a cambered airfoil where α {\displaystyle \alpha \!} is the angle of attack measured relative to the zero-lift line instead of

5400-403: The following reason: for achieving a different behaviour during different flight phases, the ratio of the rotation frequency to the forward velocity has a U-shaped function, i.e., its derivative crosses 0. Practically, it means that the boomerang being at the furthest point has a very low forward velocity. The kinetic energy of the forward component is then stored in the potential energy . This

5490-566: The ground, sometimes climbing gently, perform a graceful, anti-clockwise, circular or tear-drop shaped arc, flatten out and return in a hovering motion, coming in from the left or spiralling in from behind. Ideally, the hover will allow a practiced catcher to clamp their hands shut horizontally on the boomerang from above and below, sandwiching the centre between their hands. The grip used depends on size and shape; smaller boomerangs are held between finger and thumb at one end, while larger, heavier or wider boomerangs need one or two fingers wrapped over

SECTION 60

#1732845492354

5580-586: The gusts to launch their boomerang. A world record achievement was made on 3 June 2007 by Tim Lendrum in Aussie Round. Lendrum scored 96 out of 100, giving him a national record as well as an equal world record throwing an "AYR" made by expert boomerang maker Adam Carroll. In international competition, a world cup is held every second year. As of 2017, teams from Germany and the United States dominated international competition. The individual World Champion title

5670-576: The integrity of the ecoregion. The south-eastern coast of the Bird's Head Peninsula forms part of the Teluk Cenderawasih National Park . Archaeological findings indicate that local settlement dates back at least 26,000 years BP. Today, most people live in villages along the coast, with small concentrations inland. Villagers practise subsistence farming by shifting cultivation of copra , rice , maize and peanuts , as well as hunting. There are more than 80 villages scattered around

5760-791: The laminar flow, making it turbulent. For example, with rain on the wing, the flow will be turbulent. Under certain conditions, insect debris on the wing will cause the loss of small regions of laminar flow as well. Before NASA's research in the 1970s and 1980s the aircraft design community understood from application attempts in the WW II era that laminar flow wing designs were not practical using common manufacturing tolerances and surface imperfections. That belief changed after new manufacturing methods were developed with composite materials (e.g. laminar-flow airfoils developed by Professor Franz Wortmann for use with wings made of fibre-reinforced plastic ). Machined metal methods were also introduced. NASA's research in

5850-594: The leading edge to have a lot of length to slowly shock the supersonic flow back to subsonic speeds. Generally such transonic airfoils and also the supersonic airfoils have a low camber to reduce drag divergence . Modern aircraft wings may have different airfoil sections along the wing span, each one optimized for the conditions in each section of the wing. Movable high-lift devices, flaps and sometimes slats , are fitted to airfoils on almost every aircraft. A trailing edge flap acts similarly to an aileron; however, it, as opposed to an aileron, can be retracted partially into

5940-510: The left or right depends upon the design of the boomerang itself, not the thrower. A right-handed or left-handed boomerang can be thrown with either hand, but throwing a boomerang with the non-matching hand requires a throwing motion that many throwers find awkward. The following technique applies to a right-handed boomerang; the directions are mirrored for a left-handed boomerang. Different boomerang designs have different flight characteristics and are suitable for different conditions. The accuracy of

6030-433: The lift curve. At about 18 degrees this airfoil stalls , and lift falls off quickly beyond that. The drop in lift can be explained by the action of the upper-surface boundary layer , which separates and greatly thickens over the upper surface at and past the stall angle. The thickened boundary layer's displacement thickness changes the airfoil's effective shape, in particular it reduces its effective camber , which modifies

6120-433: The lift force can be related directly to the average top/bottom velocity difference without computing the pressure by using the concept of circulation and the Kutta–Joukowski theorem . The wings and stabilizers of fixed-wing aircraft , as well as helicopter rotor blades, are built with airfoil-shaped cross sections. Airfoils are also found in propellers, fans , compressors and turbines . Sails are also airfoils, and

6210-747: The moment coefficient C M = − π 2 ( α + A 0 + A 1 − A 2 2 ) = − π 2 α − ∫ 0 π d y d x ⋅ cos ⁡ ( θ ) ( 1 + cos ⁡ θ ) d θ . {\displaystyle C_{M}=-{\frac {\pi }{2}}\left(\alpha +A_{0}+A_{1}-{\frac {A_{2}}{2}}\right)=-{\frac {\pi }{2}}\alpha -\int _{0}^{\pi }{{\frac {dy}{dx}}\cdot \cos(\theta )(1+\cos \theta )\,d\theta }{\text{.}}} The moment about

6300-538: The mountain ranges have a diverse mix of sandstone, limestone, and volcanic rock. A large basin called the Kebar Valley divides the two mountain ranges. The peninsula is part of three ecoregions . The lowlands and foothills are in the Vogelkop-Aru lowland rain forests ecoregion. The New Guinea mangroves ecoregion includes coastal mangrove forests. The mountains of the peninsula above 1000 meters elevation constitute

6390-486: The overall flow field so as to reduce the circulation and the lift. The thicker boundary layer also causes a large increase in pressure drag , so that the overall drag increases sharply near and past the stall point. Airfoil design is a major facet of aerodynamics . Various airfoils serve different flight regimes. Asymmetric airfoils can generate lift at zero angle of attack, while a symmetric airfoil may better suit frequent inverted flight as in an aerobatic airplane. In

6480-414: The peninsula. There are about 18 main settlements that are the principal towns of the five regencies found on the peninsula. These cities include Bintuni , Teminabuan , Sorong , Aimas , and Manokwari . The largest settlements are the city of Sorong on the west coast and Manokwari on the east coast. Manokwari is the largest city with as of 2010 a population of 135,000 and, within the metropolitan area,

6570-409: The purely abstract. Painted surfaces are similarly richly diverse. Some boomerangs made primarily as art objects do not have the required aerodynamic properties to return. A returning boomerang is a rotating wing. It consists of two or more arms, or wings, connected at an angle; each wing is shaped as an airfoil section. Although it is not a requirement that a boomerang be in its traditional shape, it

6660-404: The region of the ailerons and near a wingtip a symmetric airfoil can be used to increase the range of angles of attack to avoid spin – stall . Thus a large range of angles can be used without boundary layer separation . Subsonic airfoils have a round leading edge, which is naturally insensitive to the angle of attack. The cross section is not strictly circular, however: the radius of curvature

6750-634: The required 20 m (66 ft), before returning to the accuracy circles on 22 March 1997 at the Australian National Championships. A boomerang was used to set a Guinness World Record with a throw of 427.2 m (1,402 ft) by David Schummy on 15 March 2005 at Murarrie Recreation Ground, Australia. This broke the record set by Erin Hemmings who threw an Aerobie 406.3 m (1,333 ft) on 14 July 2003 at Fort Funston , San Francisco. Long-distance boomerang throwers aim to have

6840-610: The south. The Arfak Mountains are a 2900-meter-high mountain range that is found in the east. Slightly lower than the Arfak Mountains, the Tamrau Mountains are found in the north. Bon Irau is the highest mountain in the Tamrau Mountains, at 2,501 meters (8,205 feet). The highest mountain on the Bird's Head Peninsula is Mount Arfak . It is 2,955 meters (9,695 feet) high and is located 21 miles southwest of Manokwari. Both of

6930-517: The straight flying (hunting) and returning variety. No one knows for sure how the returning boomerang was invented, but some modern boomerang makers speculate that it developed from the flattened throwing stick, still used by Aboriginal Australians and other indigenous peoples around the world, including the Navajo in North America. A hunting boomerang is delicately balanced and much harder to make than

7020-444: The throw depends on understanding the weight and aerodynamics of that particular boomerang, and the strength, consistency and direction of the wind; from this, the thrower chooses the angle of tilt, the angle against the wind, the elevation of the trajectory, the degree of spin and the strength of the throw. A great deal of trial and error is required to perfect the throw over time. A properly thrown boomerang will travel out parallel to

7110-422: The top edge in order to induce a spin. The aerofoil-shaped section must face the inside of the thrower, and the flatter side outwards. It is usually inclined outwards, from a nearly vertical position to 20° or 30°; the stronger the wind, the closer to vertical. The elbow of the boomerang can point forwards or backwards, or it can be gripped for throwing; it just needs to start spinning on the required inclination, in

7200-458: The total lift force F is proportional to ρ V ∫ 0 c γ ( x ) d x {\displaystyle \rho V\int _{0}^{c}\gamma (x)\,dx} and its moment M about the leading edge proportional to ρ V ∫ 0 c x γ ( x ) d x . {\displaystyle \rho V\int _{0}^{c}x\;\gamma (x)\,dx.} From

7290-583: The tourist or competition sort, and are almost invariably of the returning type. Depictions of boomerangs being thrown at animals, such as kangaroos, appear in some of the oldest rock art in the world, the Indigenous Australian rock art of the Kimberley region, which is potentially up to 50,000 years old. Stencils and paintings of boomerangs also appear in the rock art of West Papua , including on Bird's Head Peninsula and Kaimana , likely dating to

7380-534: The traditional Australian type, the cross-stick, the pinwheel, the tumble-stick, the Boomabird, and other less common types. Boomerangs return to the thrower, distinguishing them from throwing sticks. The origin of the term is uncertain. One source asserts that the term entered the language in 1827, adapted from an extinct Aboriginal language of New South Wales , Australia, but mentions a variant, wo-mur-rang , which it dates to 1798. The first recorded encounter with

7470-471: The underwater surfaces of sailboats, such as the centerboard , rudder , and keel , are similar in cross-section and operate on the same principles as airfoils. Swimming and flying creatures and even many plants and sessile organisms employ airfoils/hydrofoils, common examples being bird wings, the bodies of fish, and the shape of sand dollars . An airfoil-shaped wing can create downforce on an automobile or other motor vehicle, improving traction . When

7560-499: The very time when Aboriginal people and culture were subject to policies that removed them from their traditional lands and sought to assimilate them (physiologically and culturally) into mainstream white Australian culture, causing the Stolen Generations , Aboriginalia found an ironically "nostalgic", entry point into Australian popular culture at important social locations: holiday resorts and in Australian domestic interiors. In

7650-441: The wind is obstructed by an object such as a flat plate, a building, or the deck of a bridge, the object will experience drag and also an aerodynamic force perpendicular to the wind. This does not mean the object qualifies as an airfoil. Airfoils are highly-efficient lifting shapes, able to generate more lift than similarly sized flat plates of the same area, and able to generate lift with significantly less drag. Airfoils are used in

7740-505: The wing if not used. A laminar flow wing has a maximum thickness in the middle camber line. Analyzing the Navier–Stokes equations in the linear regime shows that a negative pressure gradient along the flow has the same effect as reducing the speed. So with the maximum camber in the middle, maintaining a laminar flow over a larger percentage of the wing at a higher cruising speed is possible. However, some surface contamination will disrupt

7830-412: The wings creates lift on both "wings". However, during one-half of each blade's rotation, it sees a higher airspeed, because the rotation tip speed and the forward speed add, and when it is in the other half of the rotation, the tip speed subtracts from the forward speed. Thus if thrown nearly upright, each blade generates more lift at the top than the bottom. While it might be expected that this would cause

7920-427: Was devised by German mathematician Max Munk and further refined by British aerodynamicist Hermann Glauert and others in the 1920s. The theory idealizes the flow around an airfoil as two-dimensional flow around a thin airfoil. It can be imagined as addressing an airfoil of zero thickness and infinite wingspan . Thin airfoil theory was particularly notable in its day because it provided a sound theoretical basis for

8010-418: Was proposed by Wallace J. Morris II in his doctoral thesis. Morris's subsequent refinements contain the details on the current state of theoretical knowledge on the leading-edge stall phenomenon. Morris's theory predicts the critical angle of attack for leading-edge stall onset as the condition at which a global separation zone is predicted in the solution for the inner flow. Morris's theory demonstrates that

8100-636: Was won in 2000, 2002, 2004, 2012, and 2016 by Swiss thrower Manuel Schütz. In 1992, 1998, 2006, and 2008 Fridolin Frost from Germany won the title. The team competitions of 2012 and 2014 were won by Boomergang (an international team). World champions were Germany in 2012 and Japan in 2014 for the first time. Boomergang was formed by individuals from several countries, including the Colombian Alejandro Palacio. In 2016 USA became team world champion. Modern boomerang tournaments usually involve some or all of

#353646