APPENDIX L: CAR SHAPE AND AERODYNAMIC DRAG
To evaluate the importance of aerodynamics to car performance, two models were
constructed for wind tunnel testing. One was intended to have bad aerodynamics the
other to have good aerodynamics.
A basic box was chosen as the bad aerodynamic shape model.
For the good aerodynamic model an airship shape was selected.
The requirement to carry cargo in the form of milk cartons means that a pure airship
shape cannot be used. To accommodate the milk cartons the shape was stretched in
length by adding a parallel section in the middle, and stretched in width by adding a wing
like section between the sides to enable the specified cargo to fit. This stretching also
allowed room for the solar panel.
The models were designed and constructed to have similar frontal areas and wetted
surface area, making them virtually identical except for shape. Both models were
constructed at ½ scale.
To evaluate the performance of these car shapes, wind tunnel testing of the models was
undertaken and the drag results obtained used in the mathematical simulator to predict
performance of full size cars manufactured with these body shapes.
WIND TUNNEL TESTING OF MODELS:
The models are pictured below in the wind tunnel for testing.
Stretched airship shape Block shape
(Frontal area 7016 mm sq.) (Frontal area 6848 mm sq.)
Test results obtained are detailed below.
Air Speed Drag readings Newtons Coefficient for simulator * Cd
M/sec Stretched Airship Block Stretched Airship Block Stretched Airship Block
8.4 0.0599 0.209 0.0034 0.0119
11.3 0.1018 0.3887 0.0032 0.0122
16.94 0.2336 0.855 0.0033 0.0119 0.1902 0.738