KNARR VS COG: A SHIPSHAPE EVALUATION: Using modern naval architecture principles on 3D model reconstructions of a Nordic cargo ship and a Hanseatic ship to assess and compare their sailing performance

During the 13th and 14th centuries, the shipbuilding traditions in the Baltic Sea and North Sea regions underwent significant transformations. From 1000 to 1300, large cargo ships built in the Nordic shipbuilding tradition dominated the maritime trade. After 1300 the supremacy in the region's maritime trade shifted to German merchants and the Hanseatic League, leading to the disappearance of the Nordic shipbuilding tradition and the rise of cogs as the most common cargo vessels in Northern Europe. Initially, the shift from Nordic ships to cogs was attributed to the latter's perceived better performance, as it was believed that it was technically impossible to build large ships in the Nordic tradition. However, this assumption was challenged when large cargo vessels built in the Nordic tradition were discovered. As a result, scholars shifted their focus from technical explanations to socio-economic ones. These socio-economic narratives linked the dominance of cogs mainly to their...Show moreDuring the 13th and 14th centuries, the shipbuilding traditions in the Baltic Sea and North Sea regions underwent significant transformations. From 1000 to 1300, large cargo ships built in the Nordic shipbuilding tradition dominated the maritime trade. After 1300 the supremacy in the region's maritime trade shifted to German merchants and the Hanseatic League, leading to the disappearance of the Nordic shipbuilding tradition and the rise of cogs as the most common cargo vessels in Northern Europe. Initially, the shift from Nordic ships to cogs was attributed to the latter's perceived better performance, as it was believed that it was technically impossible to build large ships in the Nordic tradition. However, this assumption was challenged when large cargo vessels built in the Nordic tradition were discovered. As a result, scholars shifted their focus from technical explanations to socio-economic ones. These socio-economic narratives linked the dominance of cogs mainly to their lower shipbuilding costs, as well as the commercial, political, and military power of the Hanseatic League. Besides the differences in building techniques, Nordic cargo ships and cogs had very different hull shapes and therefore differences in performance are to be expected even when comparing ships of similar sizes. However, a comprehensive performance comparison between Nordic cargo ships and cogs has not been made since most shipwrecks are only partially preserved, and the evaluation of ship performance requires a complete hull. The 3D model reconstruction of shipwrecks provides thus an opportunity to evaluate the performance capabilities of ancient vessels. This thesis aims to apply modern naval engineering approaches, typically used for modern ships, to assess and compare the performance of Nordic cargo ships and cogs using 3D reconstruction models. The goal is to determine whether the socio-economic reasons for the shift from Nordic cargo ships to cogs went hand in hand with an improvement in ship performance. To this purpose weight and stability calculations, as well as speed estimations and seakeeping calculations are conducted on the 3D model reconstructions of the Big Ship of Wismar, a 12th century Nordic cargo ship, and the Bremen cog, a 14th century cog of similar size. The results reveal significant differences between the Big Ship of Wismar and the Bremen cog in all the examined performance characteristics. Overall, the Big Ship of Wismar demonstrates superior transverse stability, speed, and seakeeping behaviour than the Bremen cog. These findings, together with the evidence from calculations on other ships and sea trials on full-scale replicas, indicate that the socio-economic factors had such a substantial impact on shaping the observed transformations in shipbuilding traditions, that they outweighed the reduction in ship performance. Additionally, cogs' key features, such as high freeboard, full hull lines, closed deck, and superstructure, appear to have played a crucial role in their supremacy. These characteristics not only allowed them to transport cargo in bulk, but also provided a defensive advantage against attacks. While Nordic cargo ships exhibited superior speed, stability, and seaworthiness, cogs were more suitable for meeting the social demands of the time. This thesis demonstrates that modern naval architecture methods can effectively be applied to 3D model reconstructions of ancient ships to enhance the understanding of ship performance in maritime archaeology. Additionally, it proves that evaluating ship performance can provide valuable insights on broader research questions, such as understanding the social changes that would have influenced and driven the transformative processes observed in shipbuilding traditions.Show less

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KNARR VS COG: A SHIPSHAPE EVALUATION: Using modern naval architecture principles on 3D model reconstructions of a Nordic cargo ship and a Hanseatic ship to assess and compare their sailing performance