World's Largest Medieval Cog

Professor Lucy Blue speaks with Otto Uldum, Maritime Archaeologist and curator at the Viking Ship Museum in Roskilde, Denmark about the remarkable discovery of a medieval cog found in 2021 in 14 metres of water in the Øresund Strait near Copenhagen. Dendrochronological analysis of the sapwood date the vessel to the early fifteenth century and confirmed that it was built in the Netherlands, while some of the planking timber originated from Pomerania in present-day Poland, revealing the far-reaching timber trade networks of the period.

The ship displays distinctive cog shipbuilding techniques, including scarf joints, clinker planking, clench nailing, and square-section iron nails, all of which created a hull that was both light and exceptionally strong. Unlike many other vessels, cogs were characterised by a broad flat-bottomed midship section that enabled them to carry cargoes of up to 300 tons. Named Svælget 2, the vessel measures 28 metres in length and is among the largest and best-preserved medieval cog ever discovered. Every surviving timber has now been raised and laser-scanned, and once conservation is complete the ship will be reassembled alongside its extensive rigging assemblage, including a rare complete set of deadeyes with surviving rope fragments. Many questions, however, remain unanswered. The nature of its cargo is still unknown, and the circumstances of its loss remain elusive. Could Svælget 2 represent the last gasp of cog usage within the trading networks of the Hanseatic League?