Yes, but if the Scandinavian rock carvings are not depicting skin boats then what are they? They cannot be log boats so are you suggesting that they are plank built? Could be, but I still favour skin over a flexible wooden frame and the double prow is very suggestive of that.

Much later, when the Scandinavian plank boats did emerge, they were quite different in shape such as the Nydam (see http://www.abc.se/~m10354/uwa/nydam-e.htm) which evolved into the carvel ships of Sutton Hoo and the Vikings.