A method of manufacturing a wind turbine blade component (50; 150; 250; 350; 450; 550) in form of an I-shaped shear web, the shear web having a web body and a first web foot flange at a first end of the web body and a second web foot flange at a second end of the web body, wherein the method comprises the steps of: a) providing an elongated lower web mould part (100; 200; 700; 900; 1000, 1001)having a moulding surface with a central portion, which is substantially flat, a first downwardly extending moulding surface portion at a first end of the lower web mould part (100; 200; 700; 900; 1000, 1001), and a second downwardly extending moulding surface portion at a second end of the lower web mould part (100; 200; 700; 900; 1000, 1001), wherein the first and the second moulding surface portion are diverging from the central portion along at least a part of the elongated lower web mould part (100; 200; 700; 900; 1000, 1001), b) arranging a number of first fibre layers (110; 710, 710'; 810'; 1010; 1110; 1210) on top of the elongated lower web mould part (100; 200; 700; 900; 1000, 1001) and covering the first downwardly extending moulding surface portion, the central portion, and the second downwardly extending moulding surface portion, c) arranging a number of second fibre layers (130; 730, 730'; 830'; 1030; 1130; 1230) on top of the first fibre layers (110; 710, 710'; 810'; 1010; 1110; 1210), d) arranging an upper web mould part (160; 260; 760; 1060') on top of the second fibre layers (130; 730, 730'; 830'; 1030; 1130; 1230), the upper web mould part (160; 260; 760; 1060') having a moulding surface with a central portion, which is substantially flat, a first upwardly extending moulding surface portion at a first end of the upper web mould part (160; 260; 760; 1060'), and a second upwardly extending moulding surface portion at a second end of the upper web mould part (160; 260; 760; 1060'), wherein the first and the second moulding surface portion are converging from the central portion along at least a part of the elongated upper web mould part (160; 260; 760; 1060'), e) wrapping ends of the second fibre layers (130; 730, 730'; 830'; 1030; 1130; 1230) against the first and the second upwardly extending moulding surface of the upper web mould part (160; 260; 760; 1060'), f) forming a mould cavity via the lower web mould part (100; 200; 700; 900; 1000, 1001) and upper web mould part (160; 260; 760; 1060'), g) supplying resin to the mould cavity, and h) curing or hardening the resin in order to form said wind turbine blade component (50; 150; 250; 350; 450; 550). a) providing an elongated lower web mould part (100; 200; 700; 900; 1000, 1001)having a moulding surface with a central portion, which is substantially flat, a first downwardly extending moulding surface portion at a first end of the lower web mould part (100; 200; 700; 900; 1000, 1001), and a second downwardly extending moulding surface portion at a second end of the lower web mould part (100; 200; 700; 900; 1000, 1001), wherein the first and the second moulding surface portion are diverging from the central portion along at least a part of the elongated lower web mould part (100; 200; 700; 900; 1000, 1001), b) arranging a number of first fibre layers (110; 710, 710'; 810'; 1010; 1110; 1210) on top of the elongated lower web mould part (100; 200; 700; 900; 1000, 1001) and covering the first downwardly extending moulding surface portion, the central portion, and the second downwardly extending moulding surface portion, c) arranging a number of second fibre layers (130; 730, 730'; 830'; 1030; 1130; 1230) on top of the first fibre layers (110; 710, 710'; 810'; 1010; 1110; 1210), d) arranging an upper web mould part (160; 260; 760; 1060') on top of the second fibre layers (130; 730, 730'; 830'; 1030; 1130; 1230), the upper web mould part (160; 260; 760; 1060') having a moulding surface with a central portion, which is substantially flat, a first upwardly extending moulding surface portion at a first end of the upper web mould part (160; 260; 760; 1060'), and a second upwardly extending moulding surface portion at a second end of the upper web mould part (160; 260; 760; 1060'), wherein the first and the second moulding surface portion are converging from the central portion along at least a part of the elongated upper web mould part (160; 260; 760; 1060'), e) wrapping ends of the second fibre layers (130; 730, 730'; 830'; 1030; 1130; 1230) against the first and the second upwardly extending moulding surface of the upper web mould part (160; 260; 760; 1060'), f) forming a mould cavity via the lower web mould part (100; 200; 700; 900; 1000, 1001) and upper web mould part (160; 260; 760; 1060'), g) supplying resin to the mould cavity, and h) curing or hardening the resin in order to form said wind turbine blade component (50; 150; 250; 350; 450; 550).