Not only the asymmetrical airfoil of our blades does make the difference compared to the conventional used blades made out of fiberglass or metal, but especially the new materials CFK/Keflar and the production process.
Producing blades the conventional way there is always a problem built it torsion resistant with some flexibility along the longitudinal axis, to prevent unwanted oscillations. Every change of the angle of attack results in an torque input to the blade, if the blade is, due to its structural or material limitations not torque resistant, unwanted pitch inputs will result and the flight path will be unstable, vibrations will occur at the fuselage as well as at the engine (see Michael Kalbow, Hubschrauber Aerodynamik). Do prevent these unwanted side effects people came up with the S-type airfoil. Aerodynamically the upper airflow will hit the trailing edge of the blade which has been bent upwards, creating a turning motion to counteract the pitching motion. Needless to say this construct will increase the drag, requiring additional engine and servo power and decreasing the overall flight time. Nowadays using CFK/Keflar material and production processes quite different airfoils can be used. Our Big Scale Blades are flexible enough along the longitudinal axes to warrant stable flight conditions even if it is windy or if the helicopter got an increased fixed weight due to a fuselage or other ad on. They are very torsion resistance, no additional steering inputs to counteract torsion will be required.
The asymmetrical airfoil does have a reduced drag coefficient combined with an increased lift factor which supports the overall trend to reproduce as many details as possible in the scale area, this will, of course, increase the weight of the model. The blade itself has been designed with the center of gravity close to the tip and a small angular difference between the longitudinal axis and the rotation axis. These attributes grant smooth and stable flight characteristics during straight and level flights. The low net weight of the blade is reducing steering and mechanical forces, increasing the flight time considerably.
These blades have been developed in cooperation with the Helifactory using their helis to reach the upmost performance.
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root:
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bolt hole:
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weight/ per blade:
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max. rpm.:
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width:
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forward:
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profile:
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direction of rod:
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14mm
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6mm/with spacer
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approx 1200 g
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800
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140mm
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2-3mm
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Asymmetrical
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clockwise or counter clockwise
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