Warmatrix

Longships were galleys built and used by the Vikings of Medieval Scandinavia. The name longship stands for a collection of ship types that all followed the same general design, which evolved over several centuries. Scandianavian ships of the 6th and 7th centuries CE lacked a true keel and could not support a mast, however by the 8th century the design had improved a lot.
All longships were clinker built. First the keel was laid down, then the stems added and finally the hull was built from the bottom up. The planks of the hull overlapped and were attacked to each other with nails. The result was a flexible hull that largely moved with the waves, rather than battering against them. The design also provided a shallow draft, sometimes no more than 0.5 meters for large, seagoing ships. Each longship had a single mast with a square sail. In addition, oars were mounted on the sides. Rowers did not sit on benches, but on sea chests. The ships were steered by a side rudder at the rear, called a steerboard, on the starboard side.
Longships were quite fast, sailing 5 - 10 knots on average and up to 15 and above with good wind. In times of weak or adverse wind, or on narrow rivers, the rowers took over. Rowing speed was about 2 knots, or double that in a short sprint. Their low draft allowed the longships to sail into shallow waters, or to be pulled up onto beaches. Despite the equally low freeboard, they were seaworthy, able to take on the open ocean. Because they had no enclosed deck, sailors were exposed to the weather, which made journeys often very uncomfortable.
Longships were galleys but did not have rams, so conducted naval combat by boarding. Often they were tied together to create a single fighting platform. Despite that they were not designed as true warships, but as transports for warriors. Naval transportation was so common among vikings, that armies were often measured in units of ships (30 - 60 men, depending on time and place). Most longships carried 30 - 40 warriors.
The longship design was used both for trading vessels like the byrding and knarr; cruisers like the snekke and karve; and for warships. Traders tended to be broad to be able to hold much cargo, warships long and narrow for speed. The smallest and most common longships had about 20 'rooms', pairs of oars. The largest ones, the 'dragons', could reach 35 pairs or more. These generally had a higher freeboard and were more able to withstand rough seas, but also had a deeper draft.
The viking longship was an innovative design that ruled the northern waters for several centuries. Many of its features were incorporated into its successor, the cog.