Rodney's trials and hull lineage challenge a fixed speed ceiling

Rodney's disputed 25-knot speed during the Bismarck chase is compared with her trial performance, which came within 0.8 knots of that figure. Iowa's ability to exceed a nominal 33 knots is generally accepted, although Nelson and Rodney exceeded their own design speeds by a greater margin on trials. F3 and the Nelson design shared closely related hull forms developed from Britain's larger, faster capital-ship studies. Those earlier studies had addressed ships displacing roughly half as much again and travelling at 32-33 knots. Applying that research to a smaller, slower requirement could leave speed available beyond the guaranteed figure. In an emergency, the remaining constraint could be the machinery life the navy was willing to sacrifice.