Kolding cog or Koldingkoggen is a shipwreck that was found in Kolding Fjord in 1943. The ship was a ca. 18 m long cog built of oak around the year 1190. The wreck was examined by the National Museum of Denmark in 2001. The study discovered that Kolding cog had a stern rudder thus making it the oldest known ship to have one.
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Kolding cog Wikipedia(Text) CC BY-SA