The book Windmills explains: “When a strong gust comes, the pressure on the shutters overcomes the tension of the spring and the shutters open, spilling wind and slowing the sail.
Raamatus „Windmills ” öeldakse:„ Tugeva tuuleiili korral ületab luukidele avaldatav surve vedru pinge ning luugid avanevad ja tiibade liikumine aeglustub.