The Unicorn (created by Hergé) would have had the size and shape of a third or fourth rank vessel (third rank according to Hergé, although she had only 50 guns).

Indeed the ships were ranked according to the number of guns they carried : first rank had no less than 100 guns ; second rank between 80 and 100, third rank between 70 and 80 units and fourth rank between 50 and 60...