Design Concepts
There are three basic options for the fairing of the vehicle: no fairing, partial fairing and full fairing. A scoring matrix was used to rate these three designs based on drag reduction, weight of fairing and manufacturability. Drag reduction can be quantified by the drag coefficient of the design. Although a lightweight fairing will benefit the speed of the vehicle, all fairing designs will be manufactured with two layers of light weight carbon fiber. Manufacturability is the effort and time needed to manufacture these designs.
From the scoring matrix, it is seen that full fairing is the type of fairing that scored the highest.
Next, the shape of the fairing was considered. Two shapes chosen to be considered were the teardrop and tunafish shapes, which were suggested in the ASME HPVC Webinar. Basic CFD analysis was run to determine the drag coefficient of the two shapes. Figure 57 shows the geometry and velocity streamlines for the Teardrop shape and Figure 58 shows the geometry and velocity streamlines for the Tunafish shape.
Table 8 summarizes the obtained surface area and drag coefficient for the two shapes. A lower surface area would mean less area over which carbon fiber needs to be applied, and therefore would mean a lower weight vehicle, which could aid in attaining a higher speed.
Table 8 shows that the tunafish shape has both a lower surface area and lower drag coefficient, so therefore the tunafish shape was chosen.
The shell must enclose all of the parts of the frame and steering and also allow the driver to operate the vehicle freely. The space near the crank needs to have enough room so the rider's feet will not collide with the fairing while pedaling. To address this problem, the cylindrical volume of space that a rider would need to pedal was measured using the crank on the prototype. This cylindrical volume was modeled in Solidworks and incorporated into the assembly as shown in Figure 59.
