sin αst

Figure 6.3: Yaw moment of a given rotor with different numbers of blades [10, p. 167]
From the above figure it is clear that the alternating load of a two-bladed rotor is almost
ROTOR
levelled out in rotors with three blades. Figure 6.3 further emphasizes the disadvantages of
the one-bladed rotor. By process of elimination it is therefore concluded that the three-
bladed rotor concept is most suited for current purpose with regards to aerodynamic per-
formance, structural considerations, manufacturability and cost. It is therefore chosen for
the current rotor design.
6.2 Blade design
The developed blade design is illustrated on figure 6.4. The design is a compromise of
multiple considerations, including aerodynamic performance demands, structural re-
quirements, obtainable materials and available manufacturing methods.
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