[hat_man]

I had posted earlier that I was designing an aerocap for my truck and got so much good information that I started building the "skeleton". Life threw me a curve and I had to put it on hold. I want to thank all of you who gave me advice on the shape. I am following it as best as I can. I haven't given up just a minor set-back.

I understand the concept (but not the mechanics) of "tailgate up vs. tailgate down" and how the air coming over the cab "curls back" and "stacks up" in the bed (after hitting the raised tailgate) allowing the subsequent air to flow over the bed more efficiently

The other day on my way home from work I had a crazy idea cross my mind on air flow under the truck after the aerocap is built. I had already thought of adding a partial belly pan from approx. the rear axle to the bumper using the spare tire carriage for support.

For the sake of argument, let's assume that the first picture is the shape I am shooting for.

In the second picture I have extended the aerocap out to the same distance as the open tailgate. Would this help with efficiency or mpg? How would this effect the air flow under the truck?

In the third picture (now for the crazy idea) what would happen if someone added a "reverse tailgate" of sorts to the outside of the regular tailgate? When closed it would rest just under the aerocap extension in picture two. But when opened would it work similar to the "tailgate up" concept and allow for better airflow under the truck?

I am no aero guy for sure, I just get a mental picture and wonder how it might work. The whole idea came from seeing the fourth picture and kind of smashing it together with my aerocap idea.