supplied to the mould cavity via resin inlets not shown in order to fully wet the fibre material finally the resin is cured in order to form the first aerodynamic shell part 136 after the first aerodynamic shell part 136 has been manufactured a pre manufactured first spar cap 160 is arranged in the first recess 176 of the first aerodynamic shell part 136 the pre manufactured first spar cap 160 may advantageously have been manufactured with a first lip or wing 166 protruding from a first side 162 of the first spar cap 160 and a second lip or wing 168 protruding from a second side 164 of the first spar cap 160 the first wing 166 and the second wing 168 abut inner surfaces of the first thickened part 172 and the second thickened part 174 of the first aerodynamic shell part 136 respectively the first spar cap 160 and the first and second wings 166 168 may advantageously be dimensioned so that a small cavity 186 is created between the first spar cap 160 and the inner surface of the recess 176 an adhesive such as an epoxy based glue may have been applied to the surface.