Construction
Construction is typically of plastic, glass-reinforced plastic, aluminium or carbon fiber. Rotor blades are typically made of wood, fiberglass or carbon fiber. Models are typically purchased in kit form from one of about a dozen popular manufacturers and take 5 to 20 hours to completely assemble.
These model helicopters contain many moving parts analogous to those on full-size helicopters, from the swashplate to rotor and everything in between.
The construction of helicopters has to be more precise than for fixed-wing model aircraft, because helicopters are susceptible to even the smallest of vibrations, which can cause problems when the helicopter is in flight.
Additionally, the small size and low weight of R/C helicopters and their components means that control inputs, especially cyclic (pitch and roll) can have a very fast response, and cause a rotation rate much faster than the equivalent input might produce on a full-size aircraft. In some cases, this quick response can make the model unnecessarily difficult to fly. For this reason, most model helicopters do not use the (simpler) Bell rotor head design, but instead use the Hiller design with a flybar, or Bell-Hiller mixing, the former providing a much greater degree of stability, and the latter mixing the quick response of the Bell system with the stability of the Hiller design. Some models use the simple Bell design, but this is limited mainly to scale models that are more challenging to fly, or models using advanced electronic stabilizing equipment.
To reduce mechanical complexity and increase precision of the control of the swashplate some model helicopters use Cyclic/collective pitch mixing.
Read more about this topic: Radio-controlled Helicopter
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