The discovery of the vacuum force on windmill sails super-
seded the idea of making the total front sail area of a rotor
as large as possible. The Danish meteorologist, inventor and
college Professor, Poul la Cour (1846–1908), made a breakthrough
in the understanding of the forces on windmill sails. His research
on mill models in front of two wind tunnels took place over
the period 1896–1900. He developed a concept called the “ideal”
sail. How did he do that? What were the improvements? What
were the consequences? Before his aerodynamic research, la
...