The square sail

This apparently simple sail played a decisive role in the history of the Viking Age as he driving force behind contact and expansion.
Ole Crumlin-Pedersen, 1989

The five Skuldelevships were found without oars, sail or ropes. However, oarholes, keelsons and the mast position show that the ships were propelled by oar or sail.
The boatbuilders can reconstruct the ships' oars using the blade of an oar found loose at Skuldelev and other finds of Viking Age oars. Reconstructing the sail is a harder task. Only traces for the fastening og the rig gives an idea of how large the sails were, and how they were handled. No sails themselves have yet been found.

In 1971 The Viking Ship Museum is given the Nordland boat Rana, built in 1982 in Ranfjord, nothern Norway. A group of enthusiastic sailors are renovating the boat with its original square-sail rig, taking inspiration from living tradition. The Viking ships are 800 years older than Rana, but the design details and the sail can contribute to our study of Viking sails, and with Rana, we learn how to use a square sail.

We reconstruct the ships' sails based on traces in other contemporary ship-finds, ship motifs depicted on coins and picture stones, the Bayeux Tapestry, legal texts, sagas and skaldic verse, theoretical analyses of aero- and hydrodynamics, and practical experiments with traditional Nordic boats.

Archaeologists, historians, sailors, boatbuilders and ship reconstructors still debate the precise shape of Viking ship sails. Were they tall and narrow like those of Norwegian square-sail boats several centuries later, or were they low and wide, as depicted on the Gotland picture stones from the Viking Age? And could Viking ships ever sail close-hauled (beating to windward as clesely as possible)?

Sea trial and trial voyages bring the research out onto the water, and give us a practical starting-point for recognising and explaining details found in ship motifs. The experiments have shown that there is a necessary correlation between a sail's width and height, the shape of the hull, and the ship's performance.
Our most important results reveal that Viking ships could indeed beat to windward.