stack 112 in the first mould part 102 during the vacuum assisted resin transfer moulding process the shear web will be firmly joined to the shell of the wind turbine rotor blade to increase its stability although only one shear web 138 is present in the shown embodiment two or more shear webs could be present as well the mould core parts 134 136 are made from a structurally stable material like for example wood moreover the structurally stable material may be surrounded by a flexible member like for example foam rubber in addition each core part 134 136 is surrounded by a flexible membrane the outer surface of which may be treated with a suitable release agent when the space between the mould parts and the mould core will be evacuated after closing the mould the air pressure still present between the structurally stable material of the mould core parts 134 136 and the flexible membrane will lead to an inflation of the membrane so that the layer stack surrounding the mould core parts 134 136 is pressed against the respective mould parts in a next step as it is shown in fig8 the top fibre reinforcement layers i e those layers atop of the core material of the layer stack 112 are wound around the mould core 128 such that both ends of the layers overlap then a core material is put atop of these layers and then the lower fibre reinforcement layers of the layer stack 112 i e those which are below the core material of this stack are wound around the core material to form a layer stack 140 thereby overlapping in their.