The so-called "Bremen Cog"

In 1962, the astonishingly well-preserved wreck of the Bremen Cog was found during dredging work to expand the harbour in the Weser River. The sensational discovery posed significant problems for the researchers: dredging activities for the harbour expansion and impending ice drift on the Weser threatened the site of the discovery. Human curiosity and illegal attempts to salvage parts of the wreck led to increased time pressure.   

The wreck was secured in three separate salvage operations, including an emergency salvage. The cog could not be raised in one piece; without the supporting sand around it, the timbers would have fallen apart. Therefore, the ship was dismantled and the individual pieces were brought ashore. Yet, it proved highly challenging to mark the exact position of the ship’s individual timbers in a reconstruction drawing.

Based on the reconstruction drawing and with the aid of photographs, a team under the supervision of shipwright Werner Lahn undertook the precise reconstruction of the vessel. For the reconstruction, it was essential to preserve the original shape of the timbers by all means. However, wet wood shrinks when dried in the air and changes its shape. Therefore, the timbers had to be kept wet. 

For 600 years, the Bremen Cog was submerged in the Weser River. Its wood had become soft and spongy. Artificial wax was supposed to replace the water contained in the wood and to stabilise the cell structure. However, this would likely have caused the preserved timbers to lose their elasticity, rendering the ship’s reconstruction more difficult. Therefore, the ship was reassembled first and only then soaked in polyethylene glycol (PEG). It took eighteen years before the wood could be stabilised with minimal shrinking and under preservation of its natural appearance. 

Following the preservation process, the cog was suspended from the hall’s ceiling to great effect and presented to the public in 2000. However, even in its preserved state, the cog’s wood is a living material: it is flexible and reacts to temperature fluctuations and humidity. It soon became apparent that the hull had warped much more than initially expected. In part, this was the result of the spacious ship’s own weight, which was no longer counteracted by water pressure.

The cog was his life’s work: Beginning in 1966, Werner Lahn (left), a shipwright with many years of experience in wooden ship building, dedicated a quarter of a century to the cog’s reconstruction – first at the Focke Museum in Bremen, and then at the newly founded German Maritime Museum in Bremerhaven.

The German Maritime Museum was opened in 1975 in Bremerhaven; it is the largest museum of its kind in Germany. Its collections, research and exhibitions are centred around the subject “Man and the Sea.” The collection comprises ten original ships in the museum harbour and a large inventory of model ships, signal guns, sea charts, personal testimonials and image sources.