A monolithic skin for an aerodynamic structure is provided. The skin comprises a root end defining a root opening; a tip end opposite to the root end; a trailing-edge portion defining a slot opening extending from the root opening toward the tip end; a leading-edge portion extending spanwise from the root end to the tip end; and a middle portion extending between the trailing edge and the leading-edge portion and at least partially defining an open slot in fluid communication with the slot opening and root opening. The middle portion comprises an interior surface facing the open slot that is graded so that the middle portion decreases in thickness spanwise toward the root end. The middle portion also comprises a first integrated spar section extending from the interior surface to the tip end.