– A third type of vertical windmill is the ‘smock-mill’, which was probably a wooden derivative from the stone or brick tower-mill, and was a Dutch invention. The earliest reliable mention of such a mill is dated 1526. The name ‘smock-mill’ is derived from its resemblance to a shepherd’s smock, and it is a tapering wooden tower, with from six to twelve weather-boarded sides, although the usual number is eight. At each corner a long ‘cant-post’ stretches from a wooden sill at the base to the circular curb at the top, into which it is mortised. By the use of curved cant-posts many Dutch smock-mills were given a very pleasing waisted shape.
A fine smock-mill was standing at Durbanville in 1895, when Hendrik van Heerde painted it. This had eight sides, curved to give a slender waisted shape, which were covered by horizontal weather-boards. It was surmounted by an ogee cap with a ball finial, and was winded by means of a fantail. Around the mill, at the level of the second-storey floor, was a wooden reefing-stage supported by a number of sloping wooden struts. A doorway leading on to the reefing-stage allowed the miller to control the feed of the grain to the stones from inside the mill, and yet he could quickly go outside to adjust the sails when necessary.
According to van Heerde’s painting, the sails had stocks running along the centre of the sails and sail-bars projecting an equal amount on each side of the stock. The sails are an example of “patent-sails” which have self-adjusting shutters operated by the wind.