Station: [2] The Mill

"In Sturm und Wetter ist Gott mein Retter“, ...

... The motto, which translates as “In storm and weather, God is my saviour", was attached to the mill cap in 1824, when the mill first opened. The panel has since been renewed, but the motto is as old as the history of windmills.

Our wooden octagonal Dutch smock mill stands on a mound – in German, that fact helps to identify this particular class of mill as a Wallholländer-Mühle, a mound-based Dutch smock mill, though we don’t differentiate in English. The elevated position protects it from flooding, but it also means the sails are more exposed to the wind. The mill tower proper doesn’t move and is 15 metres or almost fifty feet tall. If you include the rotating cap, the overall height is 20 metres or 65 feet. The sails are 21 metres or almost 69 feet in diameter.

The mill tower and cap are protected by several layers of a hand-split shingles made of green oak.

The sail system, or sweep, features what’s known as “bilausche Ventikanten” – Bilau ventisails (or airfoils). They’re named after Kurt Bilau, a German aircraft engineer who developed advanced sail shapes. His sails are based on aircraft wings. Each sail consists of two folding panels, a leading edge combined with a full-length air brake on the trailing edge. When the panels are folded up, the sails turn in the wind. Counterweights suspended from a chain behind the mill keep the panels together even if the wind picks up. If it becomes too strong, the panels open up; once it drops, they fold up again. It’s a system that keeps the sails turning at a constant speed.

Whenever the wind changes direction, the fantail on the cap turns the cap and sails into the best possible position to catch the wind. The front of the sails needs to face into the wind if the mill is to extract maximum energy from the air flow. Until the invention of the fantail, the main device used to turn the mill into the wind was a tail pole (Steert in German), a long, wooden beam with which the miller himself had to turn the sails into the wind. 

Before you enter the mill, take a look at the sails and try to remember where they are. When you’ve completed your tour, take another look at them and compare their positions.

Photos: © Dagmar Trüpschuch und Förderkreis Alte Mühle Donsbrüggen