Abstract: The invention relates to a boomerang that can automatically change both elevation angle ? of blades and curve radius r of blades upon the change of rotary speed of blades (12), wherein blades (12) are made of elastically plastic film preferably selected from a group of polyvinyl chloride, polypropylene, polyethylene terephthalate, polystyrene and high impact polystyrene, the material has a specific weight of from about 0.9 g/cm3 to about 1.60 g/cm3 and as thickness from about 0.1 mm to about 1 mm; the ratio between the depth of the rear groove and blade width is from about 1/7 to about 6/7; the ratio between depth of the front groove and blade width is from about 0 to about 3/7; the elevation angle ?0 is from about 10° to about 45°; the initial curve radius r0 of the blades is longer or equal to 1/5 of the radius R of said ring (13); the ratio between the total area of said blades and the area of a circle defined by said ring (13) is from about % to about 38%.

Abstract: The invention relates to a boomerang that can automatically change both elevation angle ? of blades and curve radius r of blades upon the change of rotary speed of blades (12), wherein blades (12) are made of elastically plastic film preferably selected from a group of polyvinyl chloride, polypropylene, polyethylene terephthalate, polystyrene and high impact polystyrene, the material has a specific weight of from about 0.9 g/cm3 to about 1.60 g/cm3 and as thicknesses of from about 0.1 mm to about 1 mm; the ratio between rear groove deep and blade width is of from about 1/7 to about 6/7; the ratio between front groove deep and blade width is of from about 0 to about 3/7; the elevation angle ?0 is of from about 10° to about 45°; the initial curve radius r0 of the blades is longer or equal to ? of the radius R of said ring (13); the ratio between the total area of said blades and the area of a circle defined by said ring (13) is of from about 12.5% to about 38%.