A new doubly-curved shell element (ThickS4 element) is presented and tested for flat and singly curved configurations. The benchmark tests show good correlation for the ThickS4 element with the Abaqus S4 shell element and with 3D FEM for flat and highly curved configurations (R/t ≥ 4). For radius over thickness ratios smaller than 4 the element is not able to predict the correct behaviour. In order to give a good insight in the most critical radius over thickness ratios 1 ≤ R/t ≥ 8 a stacking sequence investigation has been done making use of the Abaqus C3D8 element. An L-shaped structure has been tested for different load combinations of in-plane, out-plane and opening-moment loading. From the investigation a clear overview of best stacking sequences for all the different loading combinations were presented as well as the ratio of ILNS versus ILSS. The results can further be used as guidelines for the initial design of composite C-spars and stringers.