I have an acquaintance that built a trailer to tow behind his van. He used it haul his streamliner bicycle to races. He claimed that it improved his mileage by filling in the negative pressure space behind the van.
The shape is a simple tear drop shape when viewed from above. The top is flat. I only have one photo of it that doesn't really show it well.
Here is a recent communication from him:
We used the Harbor Freight trailer kit to start from. Got the largest diameter tires and wheels they offered. Pretty much threw the frame part away and kept the axle and hitch.
I used 2" X .065 square tube for the main frame, 2" X .125 for the center spine to the hitch, 1" X .065 for the verticals on 2 foot spacing and 1/2" X .065 on one foot spacing for the rafters. we nailed wood forms to our back deck to form the aero shape of the 1" tube.
The skins are aluminum .065 thick 5' X 12' sheets. The height of the trailer is 5'. I put the aluminum skin on with 1/8" stainless pop rivets for most of the structure with 3/16" along the lower front. The top skins are .032" mostly because I had them from a previous project
It was made to fit behind a full sized Ford van which helped the mileage quite a bit.
It is taller then the mini van so does not do much mileage help on it
maybe if the corners were cleaned up a bit ....
....
The photo that I have is here: The side door is open and it pretty well hides the trailer.
