Details of the design work and manufacturing process for a running prototype production of 25 m long composite rotor blades for wind energy generators are presented. The blades are of the 'integrated spar design' type and consist of a glass fiber skin and a PVC core. A computer program (and its action tree) is used for the analysis of the multi-connected hybrid cross-section, in order to achieve optimal design specifications. Four tools are needed for the production of two blade types, including two molds, and milling, cutting and drilling jigs. The manufacturing processes for the molds, jigs and blades are discussed in detail. The final acceptance of the blade is based on a static test where the flexibility of the blade is checked by magnitude of load and deflection, and a dynamic test evaluating the natural frequencies in bending and torsion.