How did a ship built from overlapping planks carry Vikings across oceans?

A Viking ship carried people across oceans because it was built to bend rather than to resist. Its hull was made of overlapping planks, each row lapping over the one below like roof tiles, and joined with iron nails whose ends were hammered flat over small washers called roves. This is clinker building, and the Vikings did not invent it: the first known examples are from about 310 to 320 AD, centuries before the Viking Age.

The Nordic builders added a few refinements. They usually split oak planks along the grain instead of sawing them, which gives stronger timber, and a single plank could be as thin as an inch. The result was a hull that was strong yet supple, flexing with the waves instead of fighting them. Their sails were woven wool.

There was no single Viking ship. Warships, the longships, used oars near the coast and in rivers and a sail at sea. Cargo ships, called knarrs, were about 16 metres long, could carry up to 24 tons and depended mostly on their sail. Knarrs routinely crossed the North Atlantic carrying livestock and goods to and from Greenland and the North Atlantic islands.

The same ships could also go where a deep hull cannot. A shallow draft meant they could work in water only a metre deep and land on beaches, and they were light enough to be carried over portages. That is why one design could cross an ocean, then slide up a river toward a town.