These important parts of a complete and functional Viking ship are known only through Viking Age images, negative impressions on hulls and the like, as well as detached specialised maritime artefacts. As a consequence of the poor conditions for preservation, sails and rigging have been reconstructed primarily on an ethnographical basis in relation to evidence from key maritime archaeological finds, in particular the small well-preserved 11th century merchant ship 'Skuldelev 3'. It is true that 19th century Norwegian square-sail boats have technological features in common with Viking ships with regard to both hull and to sail and rigging. These vessels – the 750 year younger successors of the Viking ships – have come to play a primary role in the reconstruction of Viking Age sails and rigging, whereas the many images of ships on picture and runic stones, and on coins, have with time come to occupy a secondary position. This is problematic as the sails on present-day reconstructed vessels far from correspond visually with Viking Age images. The Vikings' own illustrations most commonly show sails that are twice as wide as they are high, whereas the reconstructed sails are more-or-less quadratic or higher than they are wide.
The warship 'Skuldelev 2' – the model for the Sea Stallion – is the Skuldelev site's most poorly preserved vessel. Less than a quarter of the ship remains. For example, the keelson is the only trace of the sail. This allows the position of the mast in the ship to be established, but the important tack and sheet points, which reveal the width of the sail, are unknown. The same is true of the other known Viking Age warships. It is only on the small merchant ship 'Skuldelev 3' that the width of the sail can be established precisely. And even though the Viking ships naturally all represent fundamentally the same technological tradition, there are great differences between the requirements of merchant ships and warships for sail and rigging. In reconstructing the Sea Stallion'ssail it has therefore been necessary, to a great degree, to work on the basis of experience gained from previous reconstructions as well as functional calculations. The result is an almost quadratic square sail with an area of 118 m2, slightly wider than high.
After the preliminary sea trials and last year's experimental voyage to Dublin, there can be little doubt that the Sea Stallion'ssail functions as intended. The vessel can manoeuvre in both fair wind and headwind and, as far as is known, does very much what its crew asks of it. It is also apparent that the Sea Stallion tacks admirably into the wind, which the present author, wrongly, had doubted. The ship's weak point has, on the other hand, predictably proved to be the side-rudder: the Achilles heel of all large Viking ships.
It is of course good that the sail functions, both in scientific terms and with regard to safety. However, one must not forget a fundamental experimental-archaeological doctrine: that a successfully tested hypothesis is not necessarily the same as finding the correct solution. In other words, it is not granted that the Sea Stallion'ssail is consistent with the sail that, sometime in the second half of the 11th century, brought the vessel, we today call 'Skuldelev 2', from Ireland to Roskilde Fjord. These are the terms of operation when one attempts to reconstruct the past.
A couple of years ago I defended my thesis, titled The Gotlandic picture stones and the reconstruction of Viking ships' sail. In this I called for a greater use to be made than has so far been the case of Viking Age ship images in the reconstruction of sails. On that occasion Erik Andersen who designed the Sea Stallion'ssail and rigging, made an important point: Sailing in the North Sea with a reconstruction of this calibre, is no joke, and as a consequence is it necessary to be cautious when trialling untested types of sail. One can only agree. Alone the safety-related aspects dictate that, on this experimental voyage, use was made of a sail reconstructed on the basis of the well-tested methods, developed during the last three decades at the Viking Ship Museum. Also with regard to the reference material created through the reconstruction of the other vessels from the Skuldelev site, it is necessary to maintain a uniform and common methodological foundation, even though this may meet criticism. Alternatively, the standard of reference between the reconstructions, as well as the wealth of experience developed since the reconstruction of 'Skuldelev 3', Roar Ege, in the first half of the 1980s, will be compromised.
When the experimental voyage with the Sea Stallion comes to an end, Danish Maritime Archaeology will have reached a milestone. The five Skuldelev ships, the excavation of which provided the starting signal for pioneering scientific research at an international level, have all been analysed, reconstructed as functional vessels and tested thoroughly. New aims and objectives need to be defined for research into Viking Age vessels and navigation where – despite the advances of recent decades – exciting questions remain unanswered. A completely fundamental aspect of these aims and objectives should be to introduce light and shade into our perception of the functioning of the sails of Viking Ships by incorporating, to a greater extent, contemporary images of ships in the reconstruction process – both on a desk-based and at an experimental level.
Andersen, B. & E. Andersen 1989: Råsejlet – Dragens Vinge. Roskilde.
Kastholm, O.T. 2007: Viking Age Iconography and the Square Sail. Maritime Archaeology Newsletter from Denmark, vol. 22, pp. 8-12.
Kastholm, O.T. in prep.: De gotlandske billedsten og rekonstruktionen af vikingeskibenes sejl. Aarbøger for Nordisk Oldkyndighed og Historie 2005.