Using a Wind Tunnel to Measure the Drag Coefficient with
Students Designed Dragster Cars
DESCRIPTION: A set of activities using a student wind tunnel.
CONTRIBUTED BY: Carol Hodanbosi
EDITED BY: Jonathan G. Fairman - August 1996
A Ninth Grade Science Project
Barberton High School has a subsonic open circuit wind tunnel. The
wind tunnel was deigned by NASA wind tunnel experts and built by high
school students. A project was planned that involved three ninth
grade sciences to design and manufacture small dragster cars to be
tested in the wind tunnel
The Ohio model science course of study has emphasized the need for
improved science resources and an increase in student projects. By
emphasizing the discovery approach through experimentation and
allowing the students to visualize their products in a wind tunnel,
the students will be able to appreciate the role of research and
testing in the technical world.
Building upon the resources that the high school has developed
through its partnership with NASA Glenn Research Center, the project
will have an aeronautics theme.
- Design stage
- Fifty student dragster car kits were ordered from Pitsco
Company. The kits include:
- a workbook with clear directions
- balsa wood
- grid paper
Also ordered were knives and coping saws. Paint,
varnish and decals could also be ordered from the company, if
**Included with the kits were carbon dioxide cartridges which
were removed and not given to the students.
- Students worked in groups of 2 or 3.
- The workbook gave clearly outlined steps for the students
to follow to complete their car. No weight or size restriction
was given, however, this is something that one might consider.
The car had to fit inside the test bed which was 12 inches by
12 inches by 24 inches.
- Both the styrofoam pieces and the balsa wood were tapered
from back to front, and were 4 inches by 4 inches by 10 inches
- Each team of students was encouraged to design a car that
had the least amount of drag, which was to be determined by
placing in the high school wind tunnel.
- They were allowed to paint, decorate and name their cars to
their own liking.
Twenty three cars were tested in the wind tunnel.
- Each car was numbered and an eyelet was placed in the nose
of each car.
- The test bed floor was wooden plywood. A long slot was made
in the floor to allow for one degree of freedom of motion (
forward and backward, only).
- Two large L-shaped metal strews were placed in the bottom
of each car, along the midline .
- Each car was placed one at a time into the test bed, on top
of the lengthwise slot.
- The L-shaped screw was turned so that it could pass through
the slot to the outside.
- A string was tied to the eyelet on the front of the car and
over a pulley attached to the plywood floor.
- A round hole was placed in front of the pulley, allowing
the string to pass out of the tunnel beneath the car.
- A one-hundred gram mass was tied to the other end of the
string. The mass was given enough slack so that it could rest
on an electronic scale, located just below the hole from which
the string passed.
- The electronic scale was 'zeroed ' with no weight resting
on the scale, then the one hundred gram mass was placed on
- Care was taken to insure that the cars could slide forward
and backward above the slots before actual testing was
Drag was determined by the amount that the air pushed against the
car's surface. The greater the push the air made on the car, the more
the car moved backward. The backward motion of the car caused the
string to pull on the one hundred gram mass. The more the mass was
pulled upward, the lower the scale went from the one hundred gram
reference amount. That is, the car with no drag would read 100, while
one with 20 grams of drag would have a reading of 80.
Each car was rated on two values. The first value was the lowest
scale reading obtained by that car at a particular wind speed. The
second value was the middle reading. All of the the tests involved
some vibrating, which caused the readings to rise and fall. Human
judgement was used to determine the mean of those high and low
These two values were added for each car. Then the cars were
ranked from low to high. The cars having the low values had less drag
then the cars with the high numbers.
Aerospace Activities Page
Wind Tunnel Index
The Drag Equation
Shape Efects on Drag