Renowned for the ‘Bremen Cog’ from ca. 1380, Bremen has virtually become an archive for medieval shipwrecks, with many new discoveries in the decades that were to follow the 1962 discovery (A, B). Contrary to the well-studied Bremen Cog (cf. Lahn 1992, Hoffmann & Schnall 2003), the new wrecks have barely gained a similar amount of attention. Although less well preserved, they represent a wide variety of shipbuilding traditions and reflect not only the international importance of this Hanseatic city, but also its role as point of transhipment between river and seaborne transport. In the following, three distinctive shipwrecks are introduced, amongst which the latest was excavated in 2007.¹
The Schlachte-Ship – a late 12th-/ early 13th-century extended dugout with stern-rudder
At a depth of 2.47-3.55 metres below mean sea level the remains of a stern-section carved from a dugout was made 1992 in a construction pit (Wesemann & Fick 1993, 37) (F). A rough C14 dates the wreck to 1170 ±100 while a dendro-sample from a timber below provided a terminus ante quem for 1222 ±6 (Rech 2004, 244). The spatiotemporal context is significant, as the wreck was found at the confluence of the Weser River and the – now silted up – Balge tributary, dating to a time where harbour activities shifted from the Balge to the Weser at the Schlachte bank.² The construction is hitherto unique, combining a dugout – extended by at least two strakes as indicated by joggled frames – with a skeg carved from solid wood to which a stern-rudder was mounted, as evidenced by a gudgeon. This wreck was initially interpreted as cog – thus named Schlachte Kogge – and seen as a missing link in an evolutionary development from an extended dugout to a fully planked ship (Rech 2004, 244).³ Later Ellmers, on whose opinion this interpretation was originally based, substantiated his view with the presence of sintels (Ellmers 2005, 67). This is a typical prosecutor’s fallacy, as sintels are not specific to a type, but a general feature in the shipbuilding tradition of the southern North Sea coast. In fact, the working procedure can be more effectively compared to the Utrecht-type, which also involved an extended dugout and in which sintels are used too. The recent finding that the sheer of this type was greater than formerly reconstructed gave rise to associate the Utrecht-type with the historically known hulc-type, which crescent-shaped hull it attributed to its great sheer (Van de Moortel 2009a, 234 f.). Although none of the Utrecht-types has a stern-rudder, the ‘hulc’ depictions on the 12th century Winchester und Zedelgen baptismal fonts are – perhaps not incidentally – the earliest to show such rudders. Together with the Kollerup and Kolding wrecks (Hocker & Daly 2006, 192 f.), the Schlachte wreck is one of the earliest with a stern-rudder. Despite artistic license, an English 14th-century badge also seems to support the possibility of fitting a stern-rudder to a skeg carved out from solid wood (G). Ethnographic studies have highlighted the construction of large vessels in Borneo, based on an expanded and extended dugout, which use seems to be only restricted by the availability of large trees (Petersen 2000).
The Beluga-Ship – an early 15th-century clinker vessel
The latest medieval wreck discovered in Bremen was unearthed 2007 in a rescue excavation at 0.65-1.6 metres above mean sea level in the construction pit of the Beluga-Shipping company’s headquarters at Teerhof –– a peninsular between the Weser River and a side stream (C).4 This corresponds to the high medieval ground water level at + 1.5 metres (Ortlam 1996, 30). The wreck has been preserved to a length of ca. 7 metres with 8 preserved strakes on the port side, a garboard rudiment of the starboard side, a keel and a stem fragment (H). The frames must have been carefully removed, leaving only trunnel-holes at a 50 cm interval. With respect to a launchway indicating shipbuilding activities in the direct vicinity (Bischop 2008a, 95ff.), the absence of the frames can be explained by a possible re-use, while the side planking remained there to halt river bank erosion or as a working platform for ship maintenance. In the wake of extensive deforestation, which caused an increased runoff carrying greater sediment loads into rivers in conjunction with sea level rise (cf. Behre 2003, fig. 13), the wreck was swiftly covered by fluvial deposits and building debris, while the piles were driven through its side, probably for fish-traps, as indicated by ceramic net-sinkers found in the above layers.
The sample from the planks fall into two groups, the first was of high quality Baltic oak dating into the last quarter of the 14th century5 and the second of locally cut oak from the second quarter of the 15th century. The latter seem to stem from local repairs, whereas the first seem to be imported wainscot. Particularly Baltic wainscot was in high demand because it was less knotty and bent (Wazny 2005, 119), a requirement for radially cleft plank conversion as observed in this wreck. Small ships of this period with radially cleft planks in combination with rivets and tarred wool as luting material point typologically to a southern Scandinavian – possibly Danish – origin (cf. Zwick 2012, 292). Although the main source for Danish timber imports were Halland, Blekinge and Scania (Fritzbøger 2004, 110), Danish shipbuilders are also known to have imported Baltic timber via Riga (Zunde 1998/99, 121). However, typological criteria can be misleading and other origins for such clinker construction are feasible, even the southern North Sea coast (cf. Reinders & Aalders 2006, Zwick 2010, 68 ff.).The cumbersome use of radially cleft planks – although already old-fashioned at that time – was not necessarily regarded as such by contemporaries. Radially cleft planks are stronger, as the medullary rays are left intact and thus did not have to be as thick as sawn planks. This would have enabled shipbuilders to construct comparatively light vessels that could be also manoeuvred under oars (I).
The Becks-Ship – a mid 15th-century river barge
A ca. 3.7 metre bow-section was unearthed 1989 in a silted-up side stream of the Weser River (D, E), ca. 150m off the present river bank on the premises of the Beck brewery, this wreck was initially dated to 1489 (Rech 2004, 240), but may date also a bit earlier: A new sample taken from the plank keel dates around/after 1444 and is of local provenance (Zwick 2012, 287), thus the earlier sample might stem from a later repair.6 The coarse deposits and the cross-bedding inside the wreck indicate that there must have been a considerable current and that the side arm was by no means a minor stream (cf. Ortlam 1996). The Becks Ship has been built with a half-frame system, making use of crooked timber for the sharp transition at the turn-of-the-bilge. The vessel’s vernacular use is reflected in the little investment of shaping the frames, leaving the natural curvature of the branches with a lot of sapwood, and makeshift repairs, i.e. cracks held together by sintels and a re-cut at the larboard stem-rabbet, where a new scantling was inserted after the hood-ends must have come loose in one side. The plank keel was made from a tangentially sawn oak trunk, the same arguably also applies to all other planks, judging from the plank widths. The most interesting feature is arguably the L-shaped chine girder, which has a local continuance of at least 650 years, with a similar feature in a river pram from ca. 808, and an overall tradition dating back to Roman times (cf. Vlierman 1996). Similar wrecks are mainly known from the Netherlands (Reinders 1983, Vlierman 1996, Van de Moortel 2011) and Poland (Ossowski 2009).
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Bischop, D., 2008. Werften und Wracks am Weserufer: Vorbericht über die Grabung Beluga auf dem Teerhof 2007. Bremer Archäologische Blätter 7, pp. 93–110.
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Zwick, D., 2015 (forthcoming): A 15th-century shipwreck with Scandinavian features from Bremen, Germany. In: van Tilburg (ed.), Ships and Maritime Landscapes. Proceedings of the 13th International Symposium on Boat and Ship Archaeology 8-12 October 2012 in Amsterdam, The Netherlands.
 This paper summarises an article published in 2012. A more extensive English version on the most recent discovery – the Beluga Ship – shall be published in the proceedings of the conference “Hanseatic Trade in the North Atlantic – New Discoveries from Archaeology and History” held at 29 May – 1 June 2013 in Avaldsnes, Norway.
 written records refer to buildings at the Schlachte bank in 1247 and a pile structure called the slait in 1250 (Weidinger 2002, 119).
 This idea is not new and has been – more convincingly – argued in the case of the conceptional lineage between the expanded dugout haapio or esping and the7th-century Kvalsund plank boat (cf. Crumlin-Pedersen 1970).
 Teerhof means literally ‘tar yard’, Bremen’s historical shipbuilding site. A ‘tar house’ on this peninsular was mentioned as early as 1547 (Bischop 2008a, 95 ff.) and can be attributed to the practice of heating tar as protective coating for ships, regularly found in isolated locations due to fire hazard.
 In the absence of sapwood the latest dates are determinant.
 Not necessarily though, for the lack of sapwood in the later sample.