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Fans & nacelles
The 309 wing engine nacelles are designed to fit the 90mm intake diameter WeMoTec Midi fan. The nacelles are designed for easy maintenance with good impact strength.
The tail provides a mount for the 68 mm intake diameter WeMoTec Mini fan. Again removal and maintenance of this fan is quick and easy.
Number of fans Vs number of engines
To complete the 309 model a WeMoTec mini fan is required to be installed in the in tail engine. This fan unit is integral in the mounting of the engine tail rear components, such as the exhaust cone. However, our
development model does not have a motor in this unit (although one could readily be assembled). Why? -the wing mounted engines supply more than adequate thrust. Should a keen modeller wish to proceed with a third motor, then all that may be required further than our design is
the wiring. However, caution should be exercised here. The tail engine has its own thrust angle and how this will impact on the model in the air needs to be carefully investigated. Obviously any third motor mounted will require a more forward battery location to balance the
additional tail weight. There is of course a potential additional weight penalty in 3 engines.
The other issue is that the tail engine thrust may not be equal with the wing engine thrust and further likely to be far less efficient. Thus in the design, engine #2 was not designed as a major thrust provider,
rather perhaps a small engine, providing a modest thrust output, but contributing well to the sound and visual appeal of the model. With this in mind, the fin has been designed taking a light-weight design approach.
The maiden flight was flown with the two wing engines alone.
It is up to the individual modeller to decide what motor may be suitable for the fin mounted fan. Our recommendation is the model is flown on the two wing engines, which provide more than adequate thrust to weight
ratios.
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