An airfoil having a suction surface and a pressure surface, the surfaces joined together at leading and trailing portions of the airfoil, the pressure surface converging toward the suction surface at a corner, the surface converging at the corner by an angle approximately equal to or greater than at least 30.degree., such that an air stream flowing from the leading edge and over the pressure surface separates from the pressure surface at the corner. The fan therefore has a thick nose section and is substantially thinner over the majority of its chord length. One or more guide ribs extend from the pressure surface to control the flow of boundary layer air.