Method of manufacturing a composite structure, the method comprising: a. providing a mould for forming a blade shell having an inner surface with a close to vertical portion (12, 12'), wherein the mould further comprises a plurality of clamping elements (16, 31, 32) for clamping one or more fibre layers of the composite structure, the clamping elements (31, 32) being consecutively arranged one after another along part or the entire length of the mould inner surface and the clamping elements comprising magnetically attractable elements and the mould comprising one or more first magnets embedded in the close to vertical portion (12, 12') or the clamping elements comprising second magnets and the mould comprising one or more magnetically attractable elements embedded in the close to vertical portion (12, 12') such that in use the magnetically attractable elements are attracted by the first magnets or the second magnets are attracted to the magnetically attractable elements; b. placing a fibre layer on the mould inner surface on the close to vertical portion (12, 12'), c. arranging the clamping elements on top of the fibre layer with the close to vertical portion (12, 12')such that the clamping elements create a pressing force on the fibre layer against the mould, d1. distributing a first portion of a new fibre layer on the mould inner surface, d2. removing one of the clamping elements, e. distributing a further portion of the fibre layer on a part of the mould inner surface on which the clamping element was arranged and f. rearranging the clamping element on top of the further portion, and repeating steps d - f until a stack of fibre layers is formed, wherein the method further comprises arranging a vacuum bag on top of the stack of fibre layer and the clamping elements or arranging a vacuum bag on top of a peel ply layer covering the stack of fibre layers and the clamping elements, providing a resin into the mould with the stack of fibre layers, heating for curing, and removing the clamping elements after curing. a. providing a mould for forming a blade shell having an inner surface with a close to vertical portion (12, 12'), wherein the mould further comprises a plurality of clamping elements (16, 31, 32) for clamping one or more fibre layers of the composite structure, the clamping elements (31, 32) being consecutively arranged one after another along part or the entire length of the mould inner surface and the clamping elements comprising magnetically attractable elements and the mould comprising one or more first magnets embedded in the close to vertical portion (12, 12') or the clamping elements comprising second magnets and the mould comprising one or more magnetically attractable elements embedded in the close to vertical portion (12, 12') such that in use the magnetically attractable elements are attracted by the first magnets or the second magnets are attracted to the magnetically attractable elements; b. placing a fibre layer on the mould inner surface on the close to vertical portion (12, 12'), c. arranging the clamping elements on top of the fibre layer with the close to vertical portion (12, 12')such that the clamping elements create a pressing force on the fibre layer against the mould, d1. distributing a first portion of a new fibre layer on the mould inner surface, d2. removing one of the clamping elements, e. distributing a further portion of the fibre layer on a part of the mould inner surface on which the clamping element was arranged and f. rearranging the clamping element on top of the further portion, and repeating steps d - f until a stack of fibre layers is formed, wherein the method further comprises arranging a vacuum bag on top of the stack of fibre layer and the clamping elements or arranging a vacuum bag on top of a peel ply layer covering the stack of fibre layers and the clamping elements, providing a resin into the mould with the stack of fibre layers, heating for curing, and removing the clamping elements after curing.