common type which date in
design way back into obscurity.
These are the type the Mill
carried when first built in 1794.
Each sail consists of a ‘Whip’ pr
‘Radius’ 30 feet long, firmly
fastened at right-angles to the
‘Windshaft’ and arranged in
cross form with the other three.
The whips are pierced at one
seventh of their length from the
windshaft to their extremities
with a series of holes (12 in the
present case), spaced
equidistantly and into which
‘Crossbars’ six feet long are
inserted at angles varying from
18 degrees near the windshaft
to 7 degrees at the extremity,
the framework being
completed and strengthened
by light spars connecting the
ends of the crossbars and
supported by backstrays. The
varying angles of the crossbars
correspond by inverse
proportion to the increasing
diameter velocities and give the
sail its pitch or ‘Angle of
Weather’. This frame was covered
in sail cloth to catch the wind
and the amount that could be
carried with advantage.
varied from ‘Full Sail’ to ‘Dagger
Point’ by ‘Reefing’ (like ships) to
match the wind strength.
Mill had to be stopped while
each sail in turn was ‘Furled’ or
‘Set’ by hand. In 1722 Andrew
Meikle designed a sail which had
shutters that spilled the wind to
stop the Mill running away. The
shutters coupled by a connecting
rod on each whip to powerful
adjustable springs were made of
canvas on light frames or light
wood slats like a venetian blind.
The sails still had to be stopped,
through less often, for altering
the spring tension. Some Mills
had ‘Roller Reefing’, invented by
Captain Hooper, where the
canvas was rolled in and out
using air poles to vary the area of
sail. These developments paved.