At the age of 60, he was appointed head of the naval shipyard at the main naval base of Karlskrona. Here, he built new ships and organized production series for ships based on prefabrication methods, which meant that he could deliver twenty new ships in just three years, ten ships-of-the-line and ten frigates. Chapman also became a pioneer in the application of mathematical calculations in the relation between rigging, displacement, water resistance, the center of gravity of hulls, stability and tonnage.