A closer examination of the quality of la Cour's wind tunnel shows that the wind speed varies with a factor 2 form the centre line to the edge, thus putting some inaccuracy to his results. He was probably aware of this defect, for throughout 1899 he was very careful in the experimental setup. He now worked with small wing sections, flat and curved plates, in the middle of the wind tunnel, and measured both size and direction of the resulting force, thereby discovering the advantages of curved profiles. His curved wing could produce a factor 3 better than the flat wing if there was not too much air resistance to take into account.