The technological innovation in Scandinavian ship building gave the Vikings the tactical superiority they needed to raid and subdue most of Europe and Russia during the Viking Age. Viking longships were fast, strong enough to cross open ocean, light enough to carry over portages and easy to maneuver with a shallow draft that allowed beach landings and river navigation. With these ships and the tactics that grew from their use, Vikings successfully raided, traded, conquered and settled all over Europe and parts of Russia. To the Vikings, their ships were symbols of power, capable of transporting them to war, to distant shores and even to the afterlife, as some Vikings were buried in their ships.
The unique design element of Viking ships were the overlapping planks of the hull using the lapstrake or clinker method of shipbuilding. Europeans used the carvel method of boatbuilding, where strakes or planks were fastened onto a skeleton of the ship’s ribs, and the plank edges butted up smooth from seam to seam. In any size or type of Viking ship, Norse ship builders laid the keel first, then added strakes or planks and fitted internal timbers as the last step. Planks were riveted together with strong iron rivets. The overlapping planks made Viking ships lighter and far more flexible than a same-sized carvel built ship.
Vikings used different ships for war and trade. The war ships were longer, shallower and narrower than the big, broad knarr, the boats built for trade and exploration. They also had smaller boats for carrying cargo, fishing and ferrying. The two main types were the longships for war and the knarr for trade and exploration.
Ships built for raids and war had shallow drafts that allowed for landings without the need for a harbor. Bigger-keeled European built ships needed deeper waters and a harbor for landing and unloading. The shallow draft of Viking vessels also permitted river navigation; Vikings could row or sail 100 plus miles inland in order to raid or set up an impregnable base on a river island or harborless ocean island. There they were safe from enemy attacks, even deep within the interior of a country. Longships were also fast, maneuverable and powered by both wind and oars. They were symmetrical and double-ended, which allowed them to reverse direction without turning around. Viking longships had an average speed of 5 to 10 knots, but could reach a peak speed of 15 knots.
Ships built for crossing the Atlantic were deeper, broader and sturdier, with room for people, livestock and tools. Smaller, coastal ships for trading expeditions were built to carry cargos of trade goods and light enough to carry overland. One such ship of the 11th century was 45 feet long, 11 feet broad and could carry 4.6 tons of goods. Trade and exploration ships relied primarily on wind for power and used oars only to maneuver for landings.