A set of new patent sails, or 'sweeps', were fitted to the 18th century smock mill at Herne, Kent, in May 2004. Luke Bonwick, of Bonwick MHC, was invited to supervise the construction and installation of the new sweeps which were manufactured by millwrights from IJP Building Conservation Ltd of Henley on Thames, Oxfordshire. The sweeps were commissioned by Kent County Council and were craned into place in time for the open days on National Mills Weekend, when they turned under wind power. 

The sweeps at Herne are a set of double-shuttered patents, each one being 33 feet 3.75 inches long, and 5 feet 10.75 inches wide. They have a total diameter of approximately 68 feet 8 inches.

Construction of the four sweeps was executed by Paul Sellwood, Dan Barton and Ricky Quinton, and took place over a seven week period. Two of the new sweeps have been made from laminated Baltic pine which had been air-dried and pressure treated before being glued up. These timbers were supplied ready-shaped by Cowley Engineering.

Due to the relatively high cost of laminated timber, two solid baulks were specially imported for the second pair of sweeps. These timbers have been subjected to a relatively modern technique which aims to reduce the longitudinal splitting that often appears as timber dries out. The technique uses a machine which passes microwaves through the timber to season the heart at a similar rate to the exposed areas. Time will tell whether this process has extended the life of the solid sweeps; it will also be possible to compare the durability of laminated sweeps with solid ones.

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