Despite the examination of dozens and dozens of Viking long ships there is not one piece of wood with saw marks because the Vikings never used saws (apparently.) Instead they split the planks from trees and flattened them with adzs and planes. Why because a split and planed plank is very much stronger than a sawn one and so they could use thinner planks. Thinner planks, lighter ship, lighter ship faster ship and Viking ships could reach fifteen knots. Also the ship was light enough that the rowers could portage (with the help of crews from other ships) around rapids and over obstacles their victims erected to stop them.
Or so the theory goes.
Pictured is the Gokstadt ship. Here Really a work of art although an object of horror to those such ships sailed against.
Interested in the topic? Buy Gwyn Jones’ History of The Vikings Here.