From around A.D. 800 to A.D. 1000 Viking ships toured Europe on missions of exploration, trade and raiding. This era faded away as Vikings formed new trading routes and posts both in England and throughout the European continent. Viking ships were designed to operate most efficiently given the specific task. Raiding ships needed to be light, fast and easily manoeuvred with oars. Trading ships needed to have enough room to store cargo but also last a long time and have excellent sailing capabilities. Smaller exploration ships needed to be extremely portable and yet also house men and supplies. All Viking ships needed to be strong, flexible and weather-resistant to brave the stormy waves of the Baltic Sea.
While Viking ships were revolutionary in several ways, they did not stay the same throughout the centuries of Nordic travel. New improvements were made, the different classes of ships subtlety evolved, and shipbuilding techniques changed as travel necessities changed. The classic Viking raiding ship was known as the drekar, a longship design to carry warriors across sea, while the common cargo vessel was called the knarr, designed for trade routes and featuring a wider, higher structure. Like most other ships of the age, such Viking ships were created using oak, which was valued as a hard wood capable of being shaped and resisting the corrosive waters of the ocean. However, oak was not always easy to come by (especially to the Nordic Vikings, many of whom revered the trees) so many ships were created with ash, elm, pine and other more common woods.
Viking shipwrights developed a way to create lightweight craft through a clinker construction that replaced the more traditional skeleton-structure of the ship's hull with a more organic approach. Logs were carefully hewed into planks, with one primary log being chosen for the ship's keel, the primary board running from bow to stern, curving up at the ends to support the raised hull of the ship. The other boards were carefully nailed to the keel and then to each other, following the shape of the keel in an overlapping design that curved up to form the hull in a self-enforced structure that preserved strength without the weight of rigidity like in other ships. The floor planks were attached to the keel but not to the sides of the hull, again giving the ship extra flexibility. Beams were run from one side of the ship to the other to serve as reinforcement and benches for the sailors.
As the primary structure features of the hull were built, pre-made cracks were filled with a mixture of hair and resin to make the ship waterproof. The Vikings also constructed joints and nail-capping techniques to join shorter planks across the hull. The Viking rudder was attached to the starboard side of the ship, so that the ship could be easily landed on its left side when passengers wanted to disembark quickly without risking damage to the rudder mechanism.
Masts were made of straight trunks, preferable pine or similar wood, and constructed in ways similar to other simple sailing vessels of the time. Warrior vessels may or may not have had masts, opting to focus on oars for short-distance travel and use the sail only for open ocean voyages. The durability and lightness of the Viking ships was a deciding factor in both their conquest and trade empire. Without a deep keel the ships could float over shallow waters in rivers and estuaries unlike any other vessel of their time.