Average heat-transfer coefficients are presented for four fin arrays positioned with the base vertical, 45 degrees, and horizontal while dissipating heat to room air. The fins are analyzed as constant-temperature surfaces since the lowest fin efficiency encountered was greater than 98 percent. It was found that coefficients for the vertical arrays fell 10 to 30 percent below those of similarly spaced parallel plates. The 45-degree arrays yielded results 5 to 20 percent below those of the vertical. Two flow patterns were investigated for the horizontal arrays, and it was found that the coefficients could be reduced sharply by preventing three-dimensional flow.