Abstract: A fan includes a hub and blades. A first edge of each blade is proximate an open end of the hub. A first rib is coupled to the hub and substantially aligned with a first plane intersecting the central axis and an intersection of the first edge of the first blade with the hub. The first plane is angularly spaced from a reference plane intersecting the central axis and an intersection of the first edge of the second blade with the hub. An angular spacing between the first plane and the reference plane defines one sector. A second rib is aligned with a second plane angularly positioned between the first plane and the reference plane at a location less than or equal to about (1/nR?0.05) sectors from the first plane, in which nR equals the number of ribs divided by the number of blades.