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Warmatrix

War Matrix - Cog

Viking Age 800 CE - 1066 CE, Weapons and technology

Roland von Bremen, cog replica
Roland von Bremen, cog replica
The cog was the seagoing ship of northern Europe in the High Middle Age. Its design copied a lot of features from the ships of the Vikings, like a clinker-built hull, but also introduced new ones. The planks of the hull were not riveted together, a different method was used to make it water-tight and the stern was not rounded.
The cog was developed in the 10th century CE, out of the Viking knorr, a broad trading vessel. It probably originated in Frisia or Jutland. The early cog was a coaster that used a steering oar like its predecessors and was not much different.
A century later the ship became bigger, got a keel and so developed into a seagoing vessel, the true cog. It was as broad as the knorr, with an average length-width ratio of 3:1, but had a somewhat deeper draft and especially a higher freeboard. It did not have oars liking the Viking vessels and relied on a square sail attached to a single mast. The result was a rather slow and cumbersome ship, but with a large cargo capacity. The largest cogs were about 25 - 30 meters long and had a cargo capacity of 200 tons, though the average was less than 100. The speed of a cog was about 3 - 4 knots on average, up to 6 and above with good wind.
The cog was primarily a trading ship, but could also be used for war, as naval warfare then consisted mostly of small missile fire and boarding. Here its higher freeboard gave it an advantage over smaller ships. To increase that advantage, cogs were often equipped with fore and stern castles. Because of the small differences, cog traders could be converted to warships or back in a single day.
Around the 13th century CE cogs got even bigger than before. Many were equipped with a full deck and the number of masts increased from one to two and even three. Around 1250 CE the steering oar was replaced with a stern rudder that improved maneuverability. The size of the ships kept growing until the cogs reached the limits of their design and were replaced by hulks, which were more bowl-shaped and could attain larger sizes.