How did an auxiliary vane keep Dutch windmills facing the wind?

To keep windmills facing the wind, early designs relied on manual labor, such as using a long tailpole to turn the mill body or cap. In 1745, Edmund Lee invented the fantail, an automatic control system that eliminated the need for manual adjustment.12

The fantail consists of a set of five to eight smaller vanes mounted at a right angle to the main sails. These vanes are connected via gearing to wheels that run on a track around the mill’s cap or body. When the wind changes direction, it strikes the sides of the fantail vanes, causing them to rotate. This movement engages the gears and wheels, which automatically turn the mill’s cap or body until the main sails are once again positioned squarely into the wind.12