Figure 4.15 Above: La Cour’s drawing of the pressure resultant lying over
the axis from his research report. Below: The author’s drawing
showing the pressure resultant lying to the favourable side of
4.6 The “Ideal” Windmill
follows:
(1) The resistant surfaces in the four sails should be as few as
possible, especially near the tip of the sail.
(2) The width of the sail should be nearly 1/4 or 1/5 of the
length of the sail, and almost same all over.