the shear webs 50 to form the complete box beam 10 in addition the shear webs 50 can be of various depths to vary the depth of the box beam 10 this depth can be varied along the length of the beam to account for example for the taper of a wind turbine blade fig4 shows an alternative configuration of an upper section of a modular structural composite beam 100 in this case the beam 100 is an i beam comprising only one shear web 50 located in a central socket 134 of second skin member 130 the elongate elements 40 140 which form the body 142 of the flange 105 comprise different fibre reinforced plastic materials such that elongate elements 40 may comprise for example glass fibre reinforce plastic and elongate elements 140 may comprise for example carbon fibre reinforced plastic the arrangement of the different material elongate elements 40 140 shown is fig4 is an example only and any other arrangement may be selected depending of the mechanical properties desired the beam 100 further comprises reinforcement layers 144 located between the layers of elongate elements 40 140 in the body 42 these reinforcement layers comprise predominantly multiaxial u25a1 u00b1 45 u00b0 fibre reinforced plastic and provide additional shear strength to the flange 105 reinforcement layers 144 may be included in any of the modular structural composite beam configurations described herein fig5 shows a further alternative configuration of an upper section of a modular structural composite beam 200 elongate elements 40 and the skin member 260 comprises only a single skin element 220 which partially surrounds elongate elements 40 a 40 b and 40 c of the array it will be appreciated that any number of elongate elements 40 140 may be included in the array which.