Figure 4-8

All-wood/epoxy composite Hub. Source: Stroebel et al. (1984).

conjunction with a teeter system, needs to carry only net thrust and torque to the wind turbine. The resulting design is structurally efficient and should have excellent long-life fatigue potential, but it will require some form of field assembly to allow rotors to be shipped in pieces of convenient size. A cost-effective, fatigue-proven joining system for both fiberglass and wood/epoxy surely seems within reasonable technical reach but has not been developed and verified at this time. Such a field joining technique would also be of great value for vertical axis machines, whose curving blade shape makes them particularly difficult to ship in large pieces. Many other ways to use such a system to reduce machine-installed cost may be discovered once it is available and optimized.

The least-expensive structural material for fiberglass blade construction is unidirectional roving. This is a high value-added material