Boomerang


Historical evidence also points to the use of non-returning boomerangs by the ancient Egyptians, Native Americans of California and Arizona, and inhabitants of southern India for killing birds and rabbits. Indeed, some boomerangs were not thrown at all, but were used in hand to hand combat by Indigenous Australians.


Boomerang is a flying tool with a curved shape used as a weapon or for sport. Although it is usually thought of as a wooden device, modern boomerangs used for sport are often made from carbon fibre-reinforced plastics or other high-tech materials. Historically, boomerang-like devices have also been made from bones. Boomerangs come in many shapes and sizes depending on their geographic or tribal origins and intended function. The most recognisable type is the returning boomerang, which is a throwing stick that travels in an elliptical path and returns to its point of origin when thrown correctly. A returning boomerang has uneven arms or wings, so that the spinning is lopsided to curve the path. Although non-returning boomerangs throw sticks (or kylies) were used as weapons, returning boomerangs have been used primarily for leisure or recreation. Returning boomerangs were also used as decoy birds of prey, thrown above long grass in order to frighten game birds into flight and into waiting nets. Modern returning boomerangs can be of various shapes or sizes as can be seen in the diagram of modern Boomerangs to the right of page.
Based on performance

Glider or dart. Gliders have wider wings than darts and therefore tend to fly slower in the air while darts travel over longer distances.engineering.
Paper material

Origami for display or flying. Origami, from ori meaning "folding", and kami meaning "paper") is the traditional Japanese folk art of paper folding, which started in the 17th century AD and was popularized in the mid-1900s. It has since then evolved into a modern art form. The goal of this art is to transform a flat sheet of material into a finished sculpture through folding and sculpting techniques, and as such the use of cuts or glue are not considered to be origami.
Paper, glue and scissors are used

This range of paper planes are not restricted by the natural folds and weight of paper as multiple pieces can be added to result in special performance or look.
Indoor models

Endurance helicopter and endurance airplanes. These designs can last from minutes to almost an hour by using a special type of rubber band- no battery is needed!
Balsa wood

Display or fly. Different grades of balsa wood are used for different parts of the plane. Indoor wood is always cut to size on a saw and never sanded. Sanding damages the surface layer of the wood and in wood this thin, sanding damage makes the sheets very low in stiffness. Sawing to size mitigates the damage as much as possible as the saw blade cuts much cleaner without the crushing down pressure of sanding. We cut the wood on an older CNC Bridgeport mill machine using a special industrial spindle attached to the side of the machine. The spindle/motor combination weighs about 200 lbs and has a custom machined in place arbor for the blade. The spindle is very stiff and resistant to vibration. It is rate to only move 0.0001 with a 200 lbs load on the nose. We use a 8" diameter HSS blade that is .050" wide and has 200 teeth. It has no set to the blade and clearance is from a hollow grind and trimming the blade. Blades can spin at 6500 rpm so the surface speed is very high and the cut super clean.

Wood cutting starts with selecting the blocks to cut it from. The blocks are individually measured for size and weighed for mass and then the density is calculated. For indoor wood we only use blocks that are in the range of 3 - 6 lbs/cu ft density. If you are familiar with balsa wood you will know that these are very rare blocks of wood as the average density for balsa is in the 10 - 14 lbs/cu ft range. Once the blocks are selected by density, they are then examined for straight and even grain. The blocks that pass the grain selection are then examined very closely on the end for hard growth rings. In general all blocks will have hard growth rings in the outer area and that portion is unusable for indoor wood. The blocks are then cut into billets that are about 1-1/2" wide and as tall as possible. The billets are not always cut square with the original edges of the block, but are oriented to align the medulla rays ( see www.scribd.com/doc/10506897/Timber-Growth for explanation of medulla rays).

The blocks we start with are generally 2-1/2 to 3" by 3 to 4". Sometimes if the orientation of the block is perfect and the variation in hardness of the growth rings is slight, we can get 2 billets out of a block. Most often we only get one.

The propeller wood is C grain wood. That is cut with the surface of the sheet parallel to the medulla rays. Because the medulla rays are aligned radially from the centre of the tree, you have to keep rotating the billet as you cut to keep proper alignment. So for C grain the routine is orient the block on the machine, take a truing cut, cut a few sheets, re-orient and repeat.

f. Indoor models: endurance helicopter and endurance airplanes. These designs can last from minutes to almost an hour by using a special type of rubber band- no battery is needed!

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