It is the most important and the most delicate component of the wind machine. Its aerodynamic efficiency, closely linked to its proportion, determines the amount of air drawn from above and pushed down, and consequently the size of the protected surface. Designed and tested in wind tunnels, measured with analogue models and field tests, it moves large volumes of air at low speed to ensure maximum distance of air movement.
It can be manufactured in fiberglass, to enhance stress resistance, or in carbon fiber, to make it lighter and reduce the stress on the gearbox. The external surface is protected by special paints that make it resistant to atmospheric agents.