[skyking]

Originally Posted by aerostealth

This is a scale drawing of the top of my Apex trailer to show the added mods for improved aerodynamic trailer towing. The scale is 1 ft per grid line. The trailer body increases from 19.5 ft long to nearly 26 ft including both the projected front and back modification. The side width is 90 inches or 7.5 wide. The second image at the right shows a side view of the boat tail only which is showing the top angle of 25 degrees to scale. The two side panels and the bottom panel will be at a 10 degree angle as shown.

I have seen in other threads a rationale for the trailer manufacturer to optimize interior space in trailers as a reason not to improve the aerodynamics of trailers. It is my position that this rationalization is not legitimate. As can be seen by my drawing the rear boat tail could be light in weight and made fold-able for storage when not in use. The front fascia can be light weight paneling also which would cover the propane tanks, and act as an additional storage area for light weight object like bed rolls etc.

The manufacturer really does not have a good reason not to include modifications like this into their trailer designs. With fascia surrounds for the AC unit if top mounted, and under belly enclosures to clean up the air under the trailer they would have a much better product that could cost the buy up to 30% less in fuel cost to tow. You can not tell me that this would not sell if it was understood by the buyers. The manufacturer could incorporate these features much better then the Ecomodder can after the the trailer design has been finalized. They could do it better, in a more durable fashion, and with a more pleasing aesthetics then most of us can in our garage. I think such a product enhancement could breathe some new life in this moribund industry.

The real reason it is not being done is fundamental lack of comprehension and insight into the physical laws governing low speed aerodynamics and its importance. In short they just are not all that sharp of pencil in their chosen field of trailer designing.

There are DOT lighting requirements for vehicles over 80" wide.
My solution is to make a folding boat tail, or one you put together, that attaches to pull-out clearance light bar above and bumper/taillight assemblies below. Then you meet the lighting requirements, and provide a stiffening structure. Put an x-brace like yours in the back when done and it would be strong.
Now you have a 5 or more foot extension with plan taper, and a rear diffuser makes it a nice 4 sided cavity that should "let go" of the wake as good as it can be done.
Fold it up and stow it and you can still get into your tight spaces.