In 1776, Chapman became a civilian member of the Board of the Admiralty. His influence on the board and favor with the king resulted in critical reports of the current habit of the high seas navy to keep old ships afloat at great expense rather than spending more resources on building new, improved ships. Chapman's recommendations for improvements of the Karlskrona facilities was also received positively and approved by the king. The same year he was elected into the Royal Swedish Academy of Sciences as member number 175.