Detroit Metro Soap Box Derby

DMSBD Tech Tips
Aerodynamics, Submitted October 31, 2001

Aerodynamics Test Results - by Amanda Karr

The tests were performed using the Tex Finsterwald coast method. From a distance of 850 ft. from the finish line we performed 10 runs down the hill. The first five runs were with the axle foils installed on the car. The next five were performed without the axle foils installed on the car. Each test number represents the distance the car traveled up the runoff hill after the finish line. I will give you feet and inches and also dismal to figure with a calculator.

With air foils installed: (Test #1 - 51' 4 5/8" 616.625) (Test # 2 - 51' 4 5/8" 616.625) (Test # 3 - 52' 9 1/8" 633.125) (Test #4 - 53' 7 1/4" 643.25) (Test #5 - 53' 7 1/4" 643.25)

Without airfoils installed: (Test # 6 - 50' 2 3/8" 602.375) (Test #7 - 50' 8 3/4" 608.75) (Test # 8 - 52' 4" 628.) (Test # 9 - 54' 648.) (Test # 10 - 53' 6 5/8" 642.625)

NOTE: Weather conditions have an affect on the tests. Here are the conditions during the tests:
Test # 1- Overcast, Test # 2 - Overcast, Test # 3 - Some Sun, Test # 4 - Overcast , Test # 5 - Overcast, Test # 6 - Overcast, Test # 7 - Overcast, Test # 8 - Sunny, Test # 9 - Sunny with tailwind, Test # 10 - Sunny with tailwind.

Final results are as follows... With the airfoils installed on the car the average distance traveled past the finish line from 850 feet up the track was 52' 5". With the airfoils removed the average distance traveled past the finish line from 850 up the track was 52' 1." Even with the last three runs with preferable sunny and tailwind conditions the car still performed better with the airfoils on an average of 4." Coast testing should really be performed on a calm day with steady conditions. With limited people and only one driver this is the method we chose. Also the car stopped within a distance of 45" for all 10 runs ! down the hill. I would attribute that to driver consistency.

Back To Tech Tips
______________________________________