A cog was a type of ship that was used during the Middle Ages, mostly for trade and transport but also in war. It first appeared in the 10th century, and was widely used from around the 12th century on. Cogs were clinker-built, generally of oak. Cogs were fitted with a single mast and a single square sail. They were used primarily for trade in north-west medieval Europe, especially by the Hanseatic League. Typical seagoing cogs were from 15 to 25 meters (49 to 82ft) long, 5 to 8 meters (16 to 26ft) wide, and were of 30–200 tons burthen. Cogs were rarely as large as 300 tons although a few were considerably larger, over 1,000 tons.
Although the name cog is recorded as early as the 9th century, the seagoing vessel of that name seems to have evolved on the Frisian coast during the 12th century. Cogs progressively replaced Viking-type vessels such as knarrs in northern waters during the 13th century. Cogs could carry more cargo than knarrs of a similar size. Their flat bottoms allowed them to settle on a level in harbour, making them easier to load and unload. Their high sides made them more difficult to board in a sea fight, which made them safer from pirates.
Description and construction
A comparison of clinker and carvel construction. Carvel frames are much heavier than clinker ribs.
Cogs were a type of round ship,[1] characterized by a flush-laid flat bottom at midships which gradually shifted to overlapped strakes near the posts. They were propelled by a single, large, rectangular sail. Typical seagoing cogs ranged from about 15 to 25 meters (49 to 82ft) in length with a beam of 5 to 8 meters (16 to 26ft) and were 40–200 tons burthen. Cogs were rarely as large as 300 tons, although a very small number were considerably larger, over 1,000 tons.[2][3][4][5] A rule of thumb for crew size was that one sailor, exclusive of any dedicated fighting men, was required for every 10 tons burthen of the cog, although this may generate a suggested crew size on the low side of Medieval practice.[6] Crews of up to 45 for civilian cogs are recorded, and 60 for a 240 ton cog being used for military transportation.[7]
Cogs were typically constructed largely of oak, and had full lapstrake, or clinker, planking covering their sides, generally starting from the bilge strakes, with double-clenchediron nails for plank fastenings. At the stem, chases are formed; that is, in each case, the land of the lower strake is tapered to a feather edge at the end of the strake where it meets the stem or stern-post. This allows the end of the strake to be fastened to the apron with the outside of the planking mutually flush at that point and flush with the stem. This means that the boat's passage through the water will not tend to lift the ends of the planking away from the stem. Before the next plank is fitted, the face of the land on the lower strake is bevelled to suit the angle at which the next strake will lie in relation with it. This varies all along the land. The new strake is held in position on the preceding one before the fastening is done.[8][9]
The keel, or keel-plank, 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 keel-plank 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 tarredmoss that was inserted into curved grooves, covered with wooden laths, and secured by metal staples called sintels.[8] The cog-built structure would be completed with a stern-mounted, hanging, central rudder on a heavy stern-post, which was a uniquely northern development.[10] The single, thick, mast was set forward of amidships, stepped into the keel-plank and equipped with a single large, rectangular, square-riggedsail.[11][9] The masts of larger vessels would be of composite construction.[12] Complicated systems of rigging were developed to support the mast and to operate the sail.[13]Cordage was usually hemp or flax[note 1] and the sail hemp-based canvas.[14] From the 13th century cogs would be decked and larger vessels would be fitted with a stern castle, to afford more cargo space by keeping the crew and tiller up, out of the way; and to give the helmsman a better view.[15]
Cross-section of hull; note the lower mast stepped and braced
A cog, compared with the carvel-built vessels more traditional in the Mediterranean, was expensive and required specialist shipwrights. However, their simpler sail setup meant that cogs only required half the crew of similar-sized vessels equipped with lateen sails, as were common in the Mediterranean.[16] A structural benefit of clinker construction is that it produces a vessel that can safely twist and flex around its long axis (running from bow to stern), which is an advantage in North Atlantic rollers, provided the vessel has a small overall displacement. A limitation of cogs is that they lack points to mount additional masts: at least some fore-and-aft sails are desirable for maneuverability but clinker-built cogs were effectively limited to a single sail.[17][18] This made them unhandy, limiting their ability to tack in the harbor and making them very reliant on wind direction at the start of voyages.[17][19] The flat bottom permitted cogs to be readily beached and unloaded at low tide when quays were not available; a useful trait when purpose-built jetties were not common.[11] Cogs were expected to have a working life of approximately 40 years.[4][note 2]
History
The 1223 seal of Lübeck, one of the leading cities of the Hanseatic League. It depicts an earlier form of cog with side rudder and curved stem and stern posts.
The earliest origins of the cog are believed to be logboats from around northern Germany. These developed into larger craft built in the same basic shape, but with planking instead of hollowed-out logs. Another development was into Kahnen, flat-bottomed boats, with pointed ends for and aft that were constructed by splitting a hollowed-out log and widening the bottom with planks that were nailed to knee-shaped ribs attached to the sides. The pointed ends (called Block locally) of the log would be cut off and attached separately to the widened hull which resulted in so-called Blockkahnen, variants of which are still in use. The earliest evidence of a cog-like craft is a clay model found in Leese on the middle Weser from the grave of an adult male who died around 200 BC. Fragments of similar clay models have been found in nearby regions.[20]
Trade from Germania in Roman times was mostly carried on Mediterranean-style sailing vessels and controlled by Roman merchants. After Roman power collapsed in the middle of the first millennium AD, transports on the large river estuaries and the sheltered waters of the Wadden Sea was taken over by Frisians who used vessels based on indigenous, flat-bottomed designs that were precursors of later medieval cogs. These had much lower sides than later cogs and would have been very similar to contemporary Scandinavian craft, such as knarrs. The oldest depiction of a vessel identified by contemporary sources as a cog is the Lübeck city seal from 1223. The early cogs were fitted with a side-mounted rudder oar that also functioned as a leeboard and was rigged with a single broad square sail that functioned similar to a lug sail.[21]
Around 1200, the side rudder began to be replaced with a centerline rudder attached to a sternpost and developed in the typical medieval cog. Cogs could carry more cargo than knarrs; the rudder made steering easier than did the steering oar of the knarr, especially for larger vessels; and cogs were cheaper to build. The latter was due to the cog's use of sawn rather than split planks which was less wasteful.[15] Fore and stern castles would later be added for defense against pirates, or to enable the use of these vessels as warships.[22] The stern castle also afforded more cargo space below by keeping the crew and tiller up, out of the way.
The reconstructed Roland von Bremen based on the wreck of a cog from around 1380
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, the Limfjord in northern Jutland offered a fairly protected passage between the North Sea and the Baltic. Due to its unusual geographical conditions and strong currents, the passage was constantly filling with sand and was completely blocked by the early 12th century. This change produced new challenges. The larger ships, which 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.[23] This resulted in major modifications to old ship structures, which can be observed by analyzing the evolution of the earliest cog finds of Kollerup, Skagen, and Kolding. This caused a boom in the number of small cogs, and the need for spacious and seaworthy ships led to the development of the cog as the workhorse of the Hanseatic League.[23] It soon became the main cargo carrier in Atlantic and Baltic waters.[18][24]
Eventually, around the 14th century, the cog reached its structural limits, and larger or more seaworthy vessels needed to be of a different type. This was the hulk, which already existed but was much less common than the cog. There is no evidence that hulks descended from cogs, but it is clear that a lot of technological ideas were adapted between the two types.[10] 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.[25]
The first archaeological find that was identified as a cog, was a ship wreck discovered in 1944 by P.J.R. Modderman in the Noordoostpolder near Emmeloord (plot NM 107). The wreck was reburied in situ and a 2008 re-excavation confirmed the interpretation as a cog. It was around 16 m long and its wood dated from 1339. The discovery by Modderman was however not well known in the literature.[26]
The most famous cog in existence today is the Bremen cog. The artifact originates from the 1380s and was discovered in 1962. Prior to this discovery, the existence of cogs was primarily documented in medieval texts and seals. In 1990 the well-preserved remains of a Hanseatic cog were discovered in the estuary sediment of the Pärnu River in Estonia which has been dated to 1300.[27] In 2012, a cog dating from the early 15th century was discovered preserved from the keel up to the decks in the silt of the River IJssel in the city of Kampen, Netherlands.[28] During its excavation and recovery an intact brick dome oven and glazed tiles were found in the galley as well as a number of other artifacts.[29][30]
In April 2022, a 13th Century cog was found in Tallinn, Estonia during highway construction. It is believed to be better preserved than the Bremen cog and a dendrochronology test on the wood has dated the wreck to 1298. The ship is 24 meters long and nine meters wide. The boards are intact up to three meters from the bottom of the ship.[31]
↑ Other materials were also used, for example walrus hide or human hair.[14]
↑ In contrast, Mediterranean-type ships built contemporaneously in the French royal shipyard of Rouen had an anticipated life of three years in north European waters.[4]
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Gardiner, Robert; Unger, Richard W., eds. (1994). Cogs, Caravels and Galleons: The Sailing Ship, 1000-1650. Conway's History of the Ship. London: Conway Maritime Press. ISBN978-0851775609.
Hutchinson, Gillian (1994). Medieval Ships and Shipping. Cranbury, NJ: Associated University Presses. ISBN9780718501174.
Holk, Andre F.L. van (2010). "Maritieme archeologie van de kogge" [Maritime archaeology of the cog]. In Brand, Hanno; Egge, Knol (eds.). Koggen, kooplieden en kantoren: de Hanze, een praktisch netwerk[Cogs, merchants and offices: the Hanse, a practical network] (hardcover) (in Dutch) (1sted.). Hilversum & Groningen: Uitgeverij Verloren & Groninger Museum. ISBN978-90-8704-165-6.
Lambert, Craig (2011). Shipping the Medieval Military: English Maritime Logistics in the Fourteenth Century. Warfare in History. Vol.34. Woodbridge, Suffolk: Boydell Press. ISBN978-1843836544.
McGrail, Sean (1981). Rafts, Boats and Ships. London: National Maritime Museum. ISBN0-11-290312-6.
Rose, Susan (1997). "Battle of Sluys". In Grove, E. (ed.). Great Battles of the Royal Navy: As Commemorated in the Gunroom, Britannia Royal Naval College, Dartmouth (illustrated [some in colour]ed.). London: Arms and Armour Press. ISBN978-1854094179.
Rose, Susan (2001). Medieval Naval Warfare 1000-1500. New York: Routledge. ISBN978-1134553105.
Runyan, Timothy (2003). Hattendorf, John B.; Unger, Richard W. (eds.). War at Sea in the Middle Ages and the Renaissance. Warfare in History. Vol.14. Woodbridge, Suffolk; Rochester, New York: Boydell Press. pp.53–68. ISBN978-0851159034.
Longships were a type of specialised Scandinavian warships that have a long history in Scandinavia, with their existence being archaeologically proven and documented from at least the fourth century BC. Originally invented and used by the Norsemen for commerce, exploration, and warfare during the Viking Age, many of the longship's characteristics were adopted by other cultures, like Anglo-Saxons, and continued to influence shipbuilding for centuries.
Viking ships were marine vessels of unique structure, used in Scandinavia from the Viking Age throughout the Middle Ages. The boat-types were quite varied, depending on what the ship was intended for, but they were generally characterized as being slender and flexible boats, with symmetrical ends with true keel. They were clinker built, which is the overlapping of planks riveted together. Some might have had a dragon's head or other circular object protruding from the bow and stern for design, although this is only inferred from historical sources. Viking ships were used both for military purposes and for long-distance trade, exploration and colonization.
Shipbuilding is the construction of ships and other floating vessels. It normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces its roots to before recorded history.
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium. On an airplane, the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane. A rudder operates by redirecting the fluid past the hull or fuselage, thus imparting a turning or yawing motion to the craft. In basic form, a rudder is a flat plane or sheet of material attached with hinges to the craft's stern, tail, or after end. Often rudders are shaped so as to minimize hydrodynamic or aerodynamic drag. On simple watercraft, a tiller—essentially, a stick or pole acting as a lever arm—may be attached to the top of the rudder to allow it to be turned by a helmsman. In larger vessels, cables, pushrods, or hydraulics may be used to link rudders to steering wheels. In typical aircraft, the rudder is operated by pedals via mechanical linkages or hydraulics.
The caravel is a small maneuverable sailing ship used in the 15th century by the Portuguese to explore along the West African coast and into the Atlantic Ocean. The lateen sails gave it speed and the capacity for sailing windward (beating). Caravels were used by the Portuguese and Castilians for the oceanic exploration voyages during the 15th and 16th centuries, during the Age of Discovery.
The koch was a special type of small one- or two-mast wooden sailing ships designed and used in Russia for transpolar voyages in ice conditions of the Arctic seas, popular among the Pomors.
Carvel built or carvel planking is a method of boat building in which hull planks are laid edge to edge and fastened to a robust frame, thereby forming a smooth surface. Traditionally the planks are neither attached to, nor slotted into, each other, having only a caulking sealant between the planks to keep water out. Modern carvel builders may attach the planks to each other with glues and fixings. It is a "frame first" method of hull construction, where the shape is determined by the framework onto which the planks are fixed. This is in contrast to "plank first" or "shell first" methods, where the outer skin of the hull is made and then reinforced by the insertion of timbers that are fitted to that shape. The most common modern "plank first" method is clinker construction; in the classical period "plank first" involved joining the edges of planks with mortise and tenon joints within the thickness of the timbers, superficially giving the smooth-hull appearance of carvel construction, but achieved by entirely different means.
Boat building is the design and construction of boats and their systems. This includes at a minimum a hull, with propulsion, mechanical, navigation, safety and other systems as a craft requires.
Clinker-built is a method of boat building in which the edges of hull planks overlap each other. Where necessary in larger craft, shorter planks can be joined end to end, creating a longer strake or hull plank.
On a vessel's hull, a strake is a longitudinal course of planking or plating which runs from the boat's stempost to the sternpost or transom. The garboard strakes are the two immediately adjacent to the keel on each side.
The birlinn or West Highland galley was a wooden vessel propelled by sail and oar, used extensively in the Hebrides and West Highlands of Scotland from the Middle Ages on. Variants of the name in English and Lowland Scots include "berlin" and "birling". The Gaelic term may derive from the Norse byrðingr, a type of cargo vessel. It has been suggested that a local design lineage might also be traceable to vessels similar to the Broighter-type boat, equipped with oars and a square sail, without the need to assume a specific Viking design influence. It is uncertain, however, whether the Broighter model represents a wooden vessel or a skin-covered boat of the currach type. The majority of scholars emphasise the Viking influence on the birlinn.
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A faering is an open boat with two pairs of oars, commonly found in most boat-building traditions in western and northern Scandinavia.
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