some more info here:
http://www.vikingeskibsmuseet.dk/en/research/ship-archaeology/hjortspring/#.VWAHK0bLOew

Its sort of a hybrid in that it does have ribs and stringer analogs, but uses sewn bevelled lapped planks to complete the 'skin'. Sometimes considered as an early example of lapstrake or clinker construction even tho' the planks joints are flush. The hull bottom is both structure and skin - sim to a logboat - and resolves to the lower end extensions.