Drafting is a tactic employed in many sports. This technique allows competitors to conserve energy by using the wake created by other athletes to pull them along. The wake provides a favorable pressure gradient to the trailing athlete. Since the pressure is low in the wake, the athlete is pushed along by the atmospheric pressure behind them. While drafting is frequently used in high-speed sports, such auto racing or bicycling, it is also an effective technique in low-speed sports, such as marathon running.

In order to study this phenomenon, scale models of runners were constructed and the drag on the trailing runner measured. This allows for the determination of the optimal position for the trailing runner. By varying the velocity in the wind tunnel, the effect of headwinds and tailwinds on this technique can be studied. A one-sixth scale model will be used as it allows for the optimization of the wind tunnel conditions.

High quality marathon runners run at an average pace of 5 minutes per mile. A 4 mile per hour headwind and tailwind are to be tested in order to determine the effect that each condition has on a runner's ability to draft.

Plastic action figure models with one sixth of the height of an actual six foot tall marathon runners were used in the equipment. One model was threaded so that it would fit directly onto the sting mount. The mounting block will be constructed to allow appropriate but variable spacing between the leading and trailing runner models. The mounting block will be of a height that allows the lead runner to be at the same height as the trail runner model that will be mounted to the sting to insure the accuracy of the data that will be gathered.

1. The electronic transducer and drag balance are calibrated.
2. The ambient conditions are determined
3. The trailing runner is mounted on the sting mount.
4. The mounting block is positioned on the floor of the test section. This precludes the mounting block from affecting the drag force on the trailing runner when the lead runner is added.
5. The drag on the trailing runner is recorded at velocities corresponding to a 5 minute mile with a zero headwind, a 4 mile per hour headwind and a 4 mile per hour tailwind.
6. The wind tunnel is stopped and the leading runner positioned in the mounting block.
7. Steps 5 and 6 are repeated with several different spacing between the leading and the trailing runners.
8. The wind tunnel is stopped and the models and the mounting block removed from the test section.

Diagrams and results of the objects may be found below.

• From the drawing determine the frontal area for each object.
• From the available table, calculate the Reynolds Number and Drag Coefficient for each object.
• Plot Drag versus Velocity for each geometry.
• Plot CD versus Re for each geometry.
• Compare with expected values and discuss.
• Determine the optimal drafting position for a marathon runner.
• Measure the energy saved by drafting.
• Study the effects of headwinds and tailwinds on drafting.