Aerodynamic Coefficients
C_D: 0.291 +/- 0.002
C_L: -0.190 +/- 0.007

Results: We expected the spoiler to increase the drag of the model, similar to the effect of a spoiler on a car. We believed this inverted airfoil would increase the downward force on the truck, resulting in an increase in the drag. However, the spoiler did indeed decrease the drag by a sizable amount. The spoiler seems to raise the effective height of the tailgate, therefore increasing the amount of circulating air and in effect allowing even less airflow to enter the bed of the truck. The nature of the airflow between the spoiler and the tailgate is not known and will be an important topic for future studies.

The top image is a picture of the truck with the spoiler. The graph below shows the convergence of the drag coefficient as Reynolds number is increased.