Viking expertise in naval craftsmanship soon led to the evolution of other types of ship. Among these were the knarr, or ocean-going cargo vessel, which facilitated far-flung trade networks and the colonization of Iceland, Greenland, and America. The knarr drew on similar design principles as the longship but was higher and wider in relation to its length and had only limited numbers of oars to assist with maneuvers in narrow channels. Cargo decks were installed fore and aft.
Proof in the planking
The secret of the Viking ship lay in its unique construction. Using a broad ax rather than a saw, expert woodworkers would first split oak tree trunks into long, thin planks. They then fastened the boards with iron nails to a single sturdy keel and then to each other, one plank overlapping the next. The Vikings gave shape to the hull using this "clinker" technique rather than the more conventional method of first building an inner skeleton for the hull.
Next, the boatbuilders affixed evenly spaced floor timbers to the keel and not to the hull; this insured resilience and flexibility. They then added crossbeams to provide a deck and rowing benches, and secured a massive beam along the keel to support the mast.
The longships' light, economic construction was a major factor behind their success. Modern replicas have achieved speeds of up to 14 knots. In marked contrast to modern sailboats, the ships' lack of a big, vertical keel meant that they were highly maneuverable and could easily penetrate shallow surf and river estuaries. Seafarers steered using a single side rudder on the right, the 'starboard' or "steering board" side. (The term 'starboard' is thought to have originated in the Viking era.) They could also reef the square sails in strong winds and adjust them to permit rapid tacking.
Preserved to the present
Famous discoveries of Viking ships at Gokstad and Oseberg, Norway, in 1880 and 1906, respectively, established the classic image of the dragon-headed warship. Longships from both sites were preserved almost intact, with lavish carved decoration, in the waterlogged clay of royal burial mounds. Built around A.D. 890, three quarters of a century after the Oseberg ship, the Gokstad vessel shows great improvements in design, particularly in the sturdiness of the mast supports. Not surprisingly, this era, during which the Norse perfected longship design, coincides with the eruption of seaborne Viking raids on the monasteries and towns of Europe.
The modern phase of Viking ship investigation began with the recovery of five vessels at Skuldelev in Roskilde fjord, Denmark, between 1957 and 1962. The excavation involved building a coffer dam around the ships, which Norsemen deliberately sunk in a desperate bid to barricade the fjord against invaders.
The major revelation at Skuldelev was the variety of the vessels, which ranged from a stocky cargo ship with a capacity of 24 tons to two sleek longships. The larger of the longships, measuring 95 feet in length, had made at least one successful crossing of the North Sea, for tree-ring analysis of its oak timbers revealed that they had been cut down around A.D. 1060-70 near Dublin, suggesting the presence of a major shipyard at this key Viking stronghold in Ireland.
Even more remarkable discoveries were to follow in 1996, when contractors began expanding Roskilde's waterfront museum, originally built to house the finds from Skuldelev. As astonishing as it sounds, no fewer than nine wrecked medieval ships eventually turned up in different spots around the building site, including one under the museum's car park.
A stunning find
The most striking discovery was the biggest longship yet found, 119 feet long, with room for at least 72 oars and a crew of 100. With its draft of only about three feet and a huge, 2,175-square-foot sail, the ship must have been swift and formidable. The excavators speculate that this ship, like the others in Roskilde harbor, may have gone down in a severe storm, then become hidden in silt. Tree-ring analysis of the high-quality oak used for its timbers suggests a construction date of around A.D. 1025.
Countless sailing experiments with replica ships continue to confirm the excellence of Viking ship design. Much less is known about Viking navigation methods on the high seas, although one of the Icelandic sagas—narratives of Norse history and legends written in Iceland in the 12th and 13th centuries—includes sailing directions from Norway to Greenland that rely on distant landmarks and the presence of birds and whales to signal the position of land. The Vikings had no compass but undoubtedly steered by the sun and stars.
Did they have other aids? The sagas contain intriguing references to a solarsteinn or 'sunstone' used for navigation. Scholars believe it possible this stone was feldspar, a mineral found in Iceland that polarizes light. Theoretically, a polarizing stone might have helped indicate the direction of the sun when clouds obscured the view. Its practicality is doubtful, however, since it would require some blue sky to work and would thus have proved useless in total overcast.
The evidence for a so-called "suncompass" is equally shaky. Some have viewed a fragment of a small wooden disk found in a Greenland monastery as a kind of bearing dial for finding north and south. The disk has a hole in its center, and the theory suggests that it originally fitted over a central pin or gnomon to cast a shadow. Markings around the edge of the disk could then have helped the navigator determine north-south. While similar modern devices do work successfully (as seen in the NOVA program "The Vikings"), many have questioned if the Greenland disc was actually used in this way. It is less than three inches across and the markings around the perimeter are so crudely carved as to make the interpretation doubtful.
"The towered ships"
The impression that a Viking fleet must have made under full sail can scarcely be imagined today, but a rhapsodizing monk at the monastery of St. Omer, France, tried his best to evoke the sailing of the royal Danish fleet in A.D. 1013:
When at length they were all gathered, they went on board the towered ships...On one side lions molded in gold were to be seen on the ships, on the other birds on the tops of the masts indicated by their movements the winds as they blew, or dragons of various kinds poured fire from their nostrils...But why should I now dwell upon the sides of the ships, which were not only painted with ornate colors but were covered with gold and silver figures?...The blue water, smitten by many oars, might be seen foaming far and wide, and the sunlight, cast back in the gleam of metal, spread a double radiance in the air.