Timber for small wind turbine blades

• Timber is very suitable for small ( < 1.5 m long) wind turbine blades.
• The mechanical strength of Sitka Spruce and Douglas Fir were determined.
• The fatigue strength of these timbers was documented in excess of one million cycles.
• A copying router was developed for cheap manufacture of the complex blade shape.

This paper addresses material properties of Douglas fir and Sitka spruce and the development of an accurate and low-cost method to manufacture small wind turbine blades. Fatigue tests performed on Douglas fir and Sitka spruce show that these timbers have excellent fatigue properties for use in small wind turbine blades. A copying router was developed and tested to manufacture timber wind turbine blades of less than about 1.5 m in length by reproducing the shape of a master turbine blade. A co-ordinate measuring machine was used to establish that the copying router has an accuracy of ± 0.5 mm when copying cylindrical bars. It reproduced the general shape and twist of a master wind turbine blade. Future versions of the copying router can be improved by reproducing the trailing edge of turbine blades with higher accuracy.