Wind turbine blades operate over a wide angle of attach range. Unlike aircraft, a wind turbine's angle of attach range extends deep into stall where the three-dimensional performance characteristics of airfoils are not generally known. Peak power predictions upon which wind turbine components are sized depend on a good understanding of a blade's post-stall characteristics. The purpose of this wind tunnel study is to characterize the performance characteristics of a blade in stall as a function of its aspect ratio, airfoil thickness, and Reynolds number. This report documents results of the wind tunnel investigation of constant chord blades having four aspect ratios, with NACA 44XX series airfoil sections, at angles of attack ranging from -10/sup 0/ to 110/sup 0/. Tests were conducted at Reynolds number ranging from 0.25 x 106 to 1.0 x 106. The thickness ratios studied were 0.18, 0.15, and 0.12, and 0.09. The aspect ratios were 6, 9, 12 and infinity. Results of force and pitching moment measurements over the angle of attack range for all combinations of Reynolds numbers, thickness, and aspect ratios, and the effects of boundary layer tripping are presented.