Aaerodynamics.
As usual then modeler had decided to have twin or multi engines model he had some
experience with single engine models. I will describe difference aerodynamics
and construction single and twin-multi models.
These differences should be understood clearly because they determine different
constructions, different pattern in usual and especially in emergency situations
then one engine stops.
1. Tail.
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Single engine model.
It has blow from rotate propeller. Rudder and elevator have efficiency then model slows. This efficiency grows with increase propeller’s RPM. If you fill lack of control you can move throttle stick ahead to give better control on rudder and elevator.
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Twin – multi engine model.
What is written above concerns elevator only. This means that efficiency of rudder
and fin in time low speed will be slow or no indolently from propeller’s RPM.
The fin and rudder will be work with certain speed only. Twin fin doesn’t have
this specific. But fin is not single problem otherwise all multi aircraft would
have number of fins = number of engines.
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2. Wing
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Single engine model.
Propeller blows on small areas of wing and ailerons. The lift of the wing depends
of flying speed. Of course the blow from propeller make some amount lift but this
amount small. The aileron’s efficiency depends of flying speed also. The lack of
aileron’s control is the first symptom than wing close to stall.
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Twin – multi model.
As you can see propellers blow on big areas of wing and ailerons. The lift of the
wing and efficiency of ailerons are high enough on slow flying speed. The wing and
ailerons will be not in stall in big range of speed. At the first sign everything
is OK but in life it is impossible. About bad news will be in the next parts of
theory.
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