Cog (ship)

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Relatively proportioned cog in the Seal of Stralsund Kogge stralsund.jpg
Relatively proportioned cog in the Seal of Stralsund

A cog is a type of ship that first appeared in the 10th century, and was widely used from around the 12th century on. Cogs were clinker-built, generally of oak, which was an abundant timber in the Baltic region of Prussia. This vessel was fitted with a single mast and a square-rigged single sail. These vessels were mostly associated with seagoing trade in medieval Europe, especially the Hanseatic League, particularly in the Baltic Sea region. They ranged from about 15 to 25 meters (49 to 82 ft) in length with a beam of 5 to 8 meters (16 to 26 ft), and the largest cog ships could carry up to about 200 tons. [1]



Stern-mounted rudder Pintle and gudgeon rudder system scheme.svg
Stern-mounted rudder

Cogs were a type of round ship, [2] characterized by a flush-laid flat bottom at midships but gradually shifted to overlapped strakes near the posts. They had full lapstrake, or clinker, planking covering the sides, generally starting from the bilge strakes, and double-clenched iron nails for plank fastenings. The keel, or keelplank, was only slightly thicker than the adjacent garboards and had no rabbet. Both stem and stern posts were straight and rather long, and connected to the keelplank through intermediate pieces called hooks. The lower plank hoods terminated in rabbets in the hooks and posts, but upper hoods were nailed to the exterior faces of the posts. Caulking was generally tarred moss that was inserted into curved grooves, covered with wooden laths, and secured by metal staples called sintels. Finally, the cog-built structure could not be completed without a stern-mounted hanging central rudder, which was a unique northern development. [3] Cogs used to have open hulls and could be rowed short distances. In the 13th century they received decks.


Cogs are first mentioned in 948 AD, in Muiden near Amsterdam. These early cogs were influenced by the Norse knarr, which was the main trade vessel in northern Europe at the time, and probably used a steering oar, as there is nothing to suggest a stern rudder in northern Europe until about 1240. [4]

Reconstruction of the cog Roland von Bremen Bremen Hansekogge RolandvonBremen.JPG
Reconstruction of the cog Roland von Bremen

Current archaeological evidence points to the Frisian coast or Western Jutland as the possible birthplace of this type of vessel. The transformation of the cog into a true seagoing trader came not only during the time of the intense trade between West and East, but also as a direct answer to the closure of the western entrance to the Limfjord. For centuries, Limfjord in northern Jutland offered fairly protected passage between the North Sea and the Baltic. Due to unusual geographical conditions and strong currents, the passage was constantly filling with sand and was completely blocked by the 12th century. This change produced new challenges. Bigger ships that could not be pulled across the sand bars had to sail around the Jutland peninsula and circumnavigate the dangerous Cape Skagen to get to the Baltic. This resulted in major modifications to old ship structures, which can be observed by analyzing evolution of the earliest cog finds of Kollerup, Skagen, and Kolding.

The need for spacious and relatively inexpensive ships led to the development of the first workhorse of the Hanseatic League, the cog. The new and improved cog was no longer a simple Frisian coaster but a sturdy seagoing trader, which could cross even the most dangerous passages. Fore and stern castles would be added for defense against pirates, or to enable use of these vessels as warships, such as used at the Battle of Sluys. The stern castle also afforded more cargo space below by keeping the crew and tiller up, out of the way.

Eventually, around the 14th century, the cog reached its structural limits, resulting in the desperate need for a quick replacement. The replacement, the hulk, already existed but awaited reconditioning. Although there is no evidence that hulks descended from the cogs, it is clear that a lot of technological ideas were adapted from one to the other and vice versa. [3] The transition from cogs to hulks was not linear. According to some interpretations, both vessels coexisted for many centuries but followed diverse lines of evolution. [5]


Reconstructed excavated cog from 1380 at Deutsches Schiffahrtsmuseum Hansekogge Bremerhaven uf.jpg
Reconstructed excavated cog from 1380 at Deutsches Schiffahrtsmuseum

The most famous cog still in existence today is the Bremen cog. It dates from the 1380s and was found in 1962; until then, cogs had only been known from medieval documents and seals.

In 1990, well-preserved remains of a Hanseatic cog were discovered in the estuary sediment of the Pärnu River in Estonia. [6] The Pärnu Cog has been dated to 1300. [6]

In 2012, a cog preserved from the keel up to the decks in the silt was discovered alongside two smaller vessels in the river IJssel in the city of Kampen, in the Netherlands. [7] The ship, dating from the early 15th century, was suspected to have been deliberately sunk into the river to influence its current. Consequently, little was expected to be found in the wreck, but during excavation and recovery in February 2016, an intact brick dome oven and glazed tiles were found in the galley as well as a number of other artifacts about the vessel. [8] [9]

See also

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Clinker built is a method of boat building where the edges of hull planks overlap each other. Where necessary in larger craft, shorter planks can be joined end to end into a longer strake or hull plank. The technique developed in northern Europe and was successfully used by the Anglo-Saxons, Frisians, Scandinavians, and typical for the Hanseatic cog. A contrasting method, where plank edges are butted smoothly seam to seam, is known as carvel construction.

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Hulk (medieval ship type) ship type

A hulk was a type of medieval sea craft, a technological predecessor of the carrack and caravel. The hulk appears to have remained a relatively minor type of sailing ship apparently peculiar to the Low Countries of Europe where it was probably used primarily as a river or canal boat, with limited potential for coastal cruising. The only evidence of hulks is from legal documents and iconography.



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  2. "Round ship". Oxford Reference. Oxford University Press. Archived from the original on 15 September 2017. Retrieved 14 September 2017.
  3. 1 2 Crumlin-Pedersen, Ole (October 2000). "To be or not to be a cog: the Bremen Cog in perspective". International Journal of Nautical Archaeology . 29 (2): 230–246. doi:10.1111/j.1095-9270.2000.tb01454.x.
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