Did I read you correct, no prop or rudder, what kit are you building? All modern U S light ships(1900-1980) had propulsion. The British lighthouse service, Trinity House, had non-self propelled lightships(as well as many european lightships). When I served on the NANTUCKET we had four Detroit Diesels, named Wine, Woman, Liberty, and Happyhour. . The three ship's generators were called Snap, Crackle, and Pop. Wow, after 33 years I still remember stuff like that, but I can't recall what I had for lunch yesterday.
Nantucket lightship: you're either scared to death or bored to death.
Mike