The Viking ship, or longboat, or longship, was not the only vessel employed by the Vikings (a generic term used here for the Northmen who plundered western Europe and the British Isles and traded along the eastern European rivers from the 8th to the 11th centuries) but is the most well-known. We are fortunate that various ships dating from the Viking era have been found in states of preservation good enough to tell us that the infamous longboat, (or “dragonship” from the dragonheads carved into the ends of the high prow and stern) was the culmination of centuries of development.
The warship of the Vikings was a clinker-built vessel, designed to be both rowed and sailed. It was flat-sided, deckless and between 10 and 30 metres long, sufficient in the latter case to hold about 100 fighting men. The oars - about 60 in the larger war-vessels (called skaithes) - were short, fairly light-weight, and would have been used in a similar fashion to the galleys of the Mediterranean. It was steered with an oar fixed to the starboard side near the stern. (See Port and Starboard).
They were very long and narrow, had a shallow draught, and displaced up to about 50 tons. They had a semi-keel in that it was only about half the length of the boat. There was a single mast amidships that held a single large square-rigged sail on a yard. When not in use, the mast was lowered towards the stern. Like with all sea-going galleys, sail-power was the usual method of propulsion, except in battle or to counter unfavourable conditions , and when negotiating rivers and other inland waterways. They were not particularly seaworthy, nor comfortable, but in them the Vikings managed to reach Greenland and North America, the Mediterranean by way of the Strait of Gibraltar and Constantinople via the rivers of eastern Europe and the Black Sea.
As well as the longboat, the northern Europeans built much broader cargo vessels, using the same construction techniques, (see Knarr) some of the later ones with more than one sail, and these would develop into the cogs and hulks of the High Middle Ages.
- Draught (sometimes draft) is the depth of water a vessel draws. The less the draught of a vessel, the shallower the water inwhich it can operate.
- The Keel, historically, is the "spine" of a ship. It is the lowest part of the vessel and to it are attached the stem and sternpost, the ribs and the bottom strakes. In nearly all sailing ships, the masts are "bedded" into it. With the advent of steel in ships, then the prolification of pleasure craft, especially racing yachts, the variations in shape, size, number and even function of keels has given the term too much weight to be treated in a mere "glossary".
- Square-rigged refers to the set of the sails on what most people would consider the classic large sailing ship – the galleon or the clipper for example, or any large warship of the age of sail. The sails are set across the bow to stern line of the vessel and are four-sided and attached to yards that can be angled according wind direction.
- Yard refers to the spar (pole) which is attached more or less half way along its length to a mast. The portions on either side are called “yardarms.” To yards are attached the standard four sided sails of the square-rigged ship. The term also refers to the cross-spar atop a lateen sail or with the trapezoid lug sails of a lugger.
- Stern The back of the boat.
Reference: "The Oxford Companion to Ships and the Sea."