the blade could be filled with a cast resin with a relatively high density eg 600 kg m 3 area 1 where the cyclic loads are highest could be filled with a cast resin mix with a density of 1000 kg m 3 the manner in which the blade is manufactured will now be described one possible manufacturing method would be to join two shell parts together and then fill the void with the filled resin this would be suitable for smaller blades but is more difficult for larger blades two moulds are prepared each of which have the configuration of one of the two halves of the blade shell a gel coat is then applied to the surface of each of these moulds and structural fibres are then placed into the tool cavities the vacuum bag is then applied and the mould fibrous material is infused with a thermoset resin which is cured in order to form the two shells if it is being used a shear web 4 running along the length of the blade is fitted and bonded into one of the halves and a dummy shear web is fitted into the upper half the dummy shear web has the same shape and size as a portion of the actual shear web which will ultimately be inserted into the second part of the blade but is coated with a release coating to allow it to be removed if bulkheads 5 are being used these are then fitted.