 In the Lexingtons longitudinal strength was challenged further by the large amount of freeboard required at the forward section of the hull to keep the ships dry and maintain a high speed in various types of weather . Also , while the 8 inches ( 200 mm ) of belt armor being considered was not an impressive amount in itself , the belt 's running potentially along 80 percent of the waterline and covering the entire side amidships made the amount of armor protection impressive by European standards . Because of the difference in ultimate tensile strength between armor steel and hull steel , severe stresses on the hull were expected . These factors plus the ships ' unusual length prompted Naval Constructor R. H. Robinson , who led the design group for the Lexingtons , to make careful analyses of strength , buoyancy and stresses expected in service . For instance , designers assumed customarily that a ship needed to withstand stresses caused by a wave of the ship 's length with a ratio of height to length of 1 : 20 . Robinson found a more reasonable ratio at 1 : 26 for the Lexingtons , which also promised considerable savings in weight . 
