• Viking square-sails;
  • woollen sails;
  • linen sails;
  • cover-factor;
  • tensile strength;
  • extension

The discovery of the five scuttled Viking ships of Roskilde Fjord in Denmark and the subsequent excavation, preservation and analysis of the remains has initiated a programme of reconstructive archaeology led by the Viking Ship Museum of Roskilde in which four of the five hulls have now been reconstructed together with their rigs and square-sails. The reconstruction of the sails has been based on fragments of heavy woollen cloth found within the roof of Trondenes church in Norway dating to the mid-13th century. This paper uses the‘cover-factor’ modelling methods of modern textile engineering to analyse the‘Viking’ sail fabrics and assess their strength, resilience and performance in comparison with the linen sails from the wreck of the Vasa.