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The history of the St. Johannismühle

The St. Johannis Mill is a windmill in Flensburg built in 1808, which stands on the corner of Kappelner Straße/An der Johannismühle on a hill in the Flensburg district of Sandberg.

Built in 1808

St. Johannis is the oldest district of Flensburg. Around St. Johannis Church, picturesque little historic houses are tucked away, from which Kappelner Strasse rises steeply to the east, past a dome on which a very special windmill was built in 1808: a so-called octagonal gallery windmill on oak pillars, which are directly supported on granite stones - without a brick foundation. Today we can only marvel at how these oak posts, over 17 m long, with their enormous cross-section, found their way from Scandinavia to Flensburg around 1800, and how the mill builders managed to erect the octagon, which has a diameter of 35 feet at the bottom and tapers to 13 ½ feet at the top, on the 7th "tablement", the topmost fixed floor.

This tower fulfils two functions that are directly intertwined: it provides space for the various mills (“gangs”) and the equipment required for them, for the storage and internal transport of the grain and the goods made from it: various types of flour, groats and barley. And it is the foundation for the wind engine, the impeller that drives the machines. A building weighing around 15 tonnes (the “cap”) was erected at a height of around 17 m for this purpose, which is mounted in such a way that the head of the impeller can be turned into the wind. The various forces that arise in this process must all be safely absorbed by the beams of the tower: hence the enormous corner posts, which were firmly fitted with the massive St. Andrew's crosses using impressive forged nails. A very special detail are the “Dutch” wedge lock connections with which the slides are firmly attached.

30er Jahre 2 - Kopie.jpg

The cap

Originally, a wooden shaft was installed that was 30 inches square. It carried the impeller with 4 sail blades at the front, the two rods were each 80 feet long. The rotation was taken up by the wooden pinion wheel with a diameter of 9 ¾ feet. After about 20 years, the wooden shaft was worn out and the Jepsen iron foundry in Flensburg was commissioned to cast a steel shaft.

Another significant change concerned the adjustment mechanism of the cap. In Germany, automatic cap tracking became widespread during the 19th century. This involved a so-called "wind rose", a transverse wind wheel mounted at the rear end of the cap, ensuring that the impeller was always directed towards the wind. This meant that the yoke and codend, which the miller had to use to manually adjust the cap while working on the gallery, were no longer needed.

And finally, the Johannismühle also received so-called “louvre wings”, which saved the miller the hard and dangerous work of using sail wings.

The decay

None of this changed the fact that the classic windmill technology had become obsolete in the first half of the 20th century. A turbine wheel produces around 60 hp in good wind, which means hard daily work, the risk that the wind will not blow or will blow too strongly, and - not to forget - the unimaginable maintenance effort associated with the wooden building being exposed to wind and weather.

This set the course for the future of the Johannismühle: in 1927 the city of Flensburg took ownership of the Johannismühle, declared it a listed building and leased the industrial monument to Johann Nissen. In 1939 a wing broke and from then on no more wind power was used. For aesthetic reasons the remaining wings were removed in 1953 and in 1954 non-functional dummy wings were added. In the last years of the 20th century the risk of accidents from falling parts had become so great that the cap was removed, the wings disposed of and the gallery removed. The roof became leaky, more and more water penetrated and the final collapse of the monument that shaped the cityscape was imminent.


The renovation

In 2021, the current owners bought the dilapidated mill including the miller's houses. With a lot of perseverance, creativity and a good dose of optimism, the miller's houses were renovated first before Prof. Dr. Lutz Fiesser and Gabriele Fiesser-Meienbrock then turned to their masterpiece - the renovation of the dilapidated mill. In more than two years of planning and construction, with long and difficult but always constructive coordination with the authorities, it was possible to solve the challenges of fire protection, statics and monument protection bit by bit and to rebuild the mill from scratch - while preserving the unique supporting structure - and to adapt it to today's standards. During the renovation of the mill, great care was taken to preserve all remaining signs of the different mill technologies. This applies in particular to the cap, but also to the mill tower, where great effort was made not to erase the traces of time, but to carefully strengthen them and make them visible in their historical context.

Pictures of the renovation

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