Doug Clarke's work across naval architecture

Did Doug Clarke specialize in a particular area of naval architecture?

Doug Clarke worked broadly across ship design, with substantial experience in hull form and displacement.

Alex Clarke remembers his father, Doug, as a generalist across naval architecture, with substantial work on hull form and displacement. He does not identify one exclusive specialty. Later, he names the Oberon class as a submarine type his father worked on. Doug also acknowledged work on nuclear submarines but would not tell his son which classes were involved.