|
It looks like you were only able to reduce your trailing wake area by about 20-25%, so a 10% reduction in drag (for a slightly smaller % reduction in highway fuel economy) would not be surprising.
In an ideal world, you'd taper the sides inward for a larger reduction in rear area. In reality, that's difficult to execute with plywood, and it's nice to have the bedrails under your aero cap. In a very ideal world, you'd taper the sides of the bed inwards, too.
You can use the same template as you did for the side view, but line up the ground plane of the template with the center line of the truck. If your shape curves inward from both sides and from the top, you can get away with sharper shapes than the template suggests. How much sharper? I do not believe anyone here can tell you (except to recommend you imitate the EV1 and Honda IMAS), so you'd be flirting with flow seperation.
But back to reality. You have a classy looking cap, and I like the overhang. If you want further drag reduction, you'll need to find room for more reduction in trailing area. You've already plucked the low-hanging fruit in that department.
|