Clinker was the predominant method of ship construction used in Northern Europe before the carvel. In clinker built hulls, the planked edges overlap; carvel construction with its strong framing gives a heavier but more rigid hull, capable of taking a variety of sail rigs. Clinker (lapstrake) construction involves longitudinal overlapping "riven timber" (split wood) planks that are fixed together over very light scantlings. A carvel boat has a smoother surface which gives the impression that it is more hydrodynamically efficient since the exposed edges of the clinker planking appear to disturb the streamline and cause drag. A clinker certainly has a slightly larger wetted area, but a carvel hull is not necessarily more efficient: for given hull strength, the clinker boat is overall lighter, and displaces less water than a heavily-framed carvel hull.