Figure 4. Scale football model (66 mm in diameter), mounted on a sting that is protected from the air flow by a shroud.

The air speed in the working section of the wind tunnel was varied from 20 m.s−1 (the minimum consistent speed achievable) up to 70 m.s−1 and back down again. The drag and lift forces experienced by the ball model were measured using the force balance at regular intervals. Three runs of tests were carried out, with the ball model mounted in three different orientations (the ball being rotated 90° about the sting between each run of tests).