Chapman recorded his extensive research of British shipbuilding in several documents, including an eight-page handwritten document titled "Directions for Building of a Ship of 50 Guns", where he described construction methods as well as the British method of launching ships. His activities attracted the interests of the British naval authorities and upon leaving Deptfort in 1753, he was arrested, his papers confiscated and was then charged with trying to lure shipyards workers into French service. France and Great Britain were at the time bitter rivals, and both Sweden and Denmark were active in uncovering British manufacturing methods as well as trying to persuade British shipwrights into their service. Chapman was kept under house arrest for about one month at the cost of half a guinea per day, though still allowed to visit London with an escort. All of his documents were returned to him except a rigging plan. After his release, he stayed a few months to study experimental physics and took lessons in engraving.