While the AeroCap is the focal point of this blog, and I am currently missing the core vehicle, there are other significant things that can be done to increase aerodynamics and reduce drag!
As found on Recumbents.com - things like Lowering the Vehicle - particularly with Ride-Height Adjustable Suspension systems that can allow the vehicle to particularly be lowered at speed, can result in improvements in aerodynamic drag - as much as 3% under the right conditions.
Underside Clean-Up - not a car wash - but an aerodynamic Clean-Up, or a full 'Body Pan' can also provide a significant improvement in Aerodynamic improvement - particularly when combined with Vehicle Lowering Activities. Make it designed for critical access areas having their own 'Inspection Doors' cut into it, with flush closing connectors.
Obviously - things out in the air spinning make drag too - so an easy addition - is to fair the Rear Wheels (Easier than the front ones, for sure), using both smooth Hub-Caps (Pizza Pans, or shallow domed style wheel covers, called - 'Racing Disks'), and Rear Wheel Well Skirts.
Rear Ends of the vehicle can also be cleaned up with a large 'Boat Tail' - or even a small one, and sometimes - a new custom 'Air Ejector' Spoiler can do a great job! Obviously - a 15% Improvement in fuel economy for a truck is great - what about a 15% improvement in Fuel Efficiency Boost!
Other items to consider (Removing) - Tall Whip Antenna's, Side View Mirrors (Replace with Side View Camera/Monitor setup), Roof Racks, or any other not used appendage in your current vehicle. Also - Blocking excess air flow inlets - to allow the vehicle to run warmer - and use less cooling air (Drag).
Other items that could be added in - include - improved Front Air Dams (To keep our airflow from under the vehicle), Hood Fairings (to smooth airflow to the windshield), and Side Fairings (to control turbulent vehicle side air flows).
To Really clean up your Vehicles Cd (Coefficient of Drag), combining all of the above elements and tuning them so the work well together - is part of the secret this Japanese Project used - to get twice the distance on the same Energy of a current 'Normal' vehicle:
Bizarre-looking Japanese EV is most aerodynamic production vehicle ever.
Here are some more Tips on making your vehicle more aerodynamic -
How to Make Your Car More Aerodynamic.
Special Vortex generators can also be used to control airflow!
Also - there are other things beside Aerodynamics improvements to reduce Gasoline (or Diesel) Consumption on your vehicle, see: 22 Ways to Make Your Car More Fuel Efficient.