sin αst

ROTOR
58
Figure 6.17: Blade attachment components
The attachment method makes it relatively easy to mount rotor blades of other materials
and designs. If necessary an intermediate component may be fastened onto the plain front
disc, making virtually any connection interface possible.
The spacing between the bolt holes, their load capacities and the thickness of the washer
are in accordance with guidelines provided by the Danish Building Research Institute
(DBRI). Appendix F contains a verification of the structural integrity of the blade attach-
ment, which also complies with these guidelines.
6.2.5 Structural calculations
The structural integrity of the blades is verified through finite element analyses that are
documented in appendix E. The analyses are based on the ultimate and fatigue load cases
of IEC 61400-2, which are derived in appendix A.3.
Verification of the structural integrity of the blade attachment is carried out analytically in
appendix F.
A modal analysis, which predicts the rotating and non-rotating natural frequencies of the
blades, is performed in appendix E.11.
6.2.6 Alternative blade design
Chapter 10 contains a preliminary investigation of the option for an alternative blade de-
sign, which may be based on simple airfoils made from e.g. cut-out sections of plastic drain
pipes or from rolled steel plates.