 After the poor performance of galleys in Russo – Swedish war of 1741 – 43 and the Pomeranian War ( 1757 – 62 ) , development of replacements became prioritized . During the Pomeranian War , trials had been made with " gun prams " ( skottpråmar ) , heavily armed , oar @-@ driven , flat @-@ bottomed barges with a shallow draft that carried guns in broadside arrangements . The prams carried more guns than the galleys , but proved far too slow to be effective . Augustin Ehrensvärd argued for new archipelago vessels that combined firepower , maneuverability , seaworthiness , and decent crew accommodations . He began a successful collaboration with shipwright Fredrik Henrik Chapman ( ennobled " af Chapman " in 1772 ) , and together they developed five new vessels : a gunboat with a 12 @-@ pounder gun and a schooner rigging , as well as four types of " archipelago frigates " ( skärgårdsfregatter ) : the smaller udema and pojama , and the larger turuma and hemmema . All four types have been called skärgårdsfregatter ( archipelago frigates ) in Swedish and English historical literature , though some authors have called the udema and pojama " archipelago corvettes " . Chapman specifically designed the archipelago frigates for service off the south coast of Finland and named them after the Finnish provinces of Uusimaa , Pohjanmaa ( Österbotten ) , Turunmaa ( Åboland ) , and Hämeenmaa ( Tavastia ) . 
