Abstract: A fan and hub assembly (60) having a plastic fan structure (62) molded to a hub (66) to achieve a predetermined resonance frequency. The hub (66) has a plurality of integrally formed arms (84) having one of more openings (88) of a predetermined size and predetermined location for permitting the flow-through of the plastic and to achieve a predetermined resonance frequency of the fan blades (64). A plurality of openings (86) are formed in the hub body (82) to permit the flow-through of liquid plastic to achieve a strong attachment of the blade root (76) to the hub (66).