Straightening the Cog

Another fine day in Tallinn behind, with good results once again, this time not only by us but also by Nikita and Kolja from SCR Group AS, who have been working hard in challenging conditions, minus 8 degrees centigrade today, to lift up the bow of the cog.

Lifting what and how come?

Well this is the 14th century wreck of a cog ship we’ve been working on for months now in the Lennusadam premises of the Estonian Maritime museum in order to preserve it to be displayed in the near future in the other location of the museum (please go back to read older postings of this blog). This means that the wreck will be moved some day, quite soon in fact, and the whole thing needs to be supported well before the move. This is what Nikita and Kolja are occupied with, constructing the supporting structures.

Bow is some 40 centimeters lower than stern and it has to be lifted up in order to assemble keel support. At the Fat Margaretha the Cog will be standing on the heavy metal keel support. At the same time, when lifting the bow up, the whole hull will be straightened. Are we scared? Yes we are!

Metal heel support waiting to be installed underneath the hull. Photo: Heikki Häyhä, FOG

Before lifting several cargo straps were attached around the hull. This was done because deck beams and all horizontal support of the hull is gone. Cargo straps keeps the hull in form during lifting operation. Lifting started by assembling heavy jacks under the keel. Every jack is having a piece of thick plywood on it in order to spread power to larger area. Rest of the keel is supported by custom made iron construction.

At the same time we have been attaching loose caulking which is falling off. This caulking is made out of Hook - moss species (Drepanocladus aduncus and Warnstorfia fluitans)[1] and originally kept in place by thin wood stripes attached with metal sintels. Metal is now gone and space between planks increased when wood has been drying. We attached loose caulking by using thin thread which goes around caulking and wood stripe and is wrapped around thin wood piece inside.

Lifting started very carefully and when we noticed that the cog is holding its form, lifting force was gradually increased. By the end of the day bow has been lifted up about 30 centimeters. Photo: Heikki Häyhä

It is amazing how well moss caulking has kept its form and how flexible it still is.

When the bow has been lifted up for 40 centimeters and the whole length of the keel supported by temporary iron supports, it is time to slide custom made keel support on its correct position. After that it will be possible to start straightening the hull. Specially the port side of the hull has been opened from both ends.

[1] Maili Roio et.al.2015. Medieval Ship finds from Kadriorg, Tallinn. In: Archaeological fieldwork in Estonia 2015