What are the large "flaps" on the back of some full-sized trailers?

The advantage is not that small , especially on long distance high speed applications.
A big problem I have seen is that all these add on's have to be adjusted and dialed in to get the desired/optimum results.
With hopping from trailer to trailer with different truck set ups most of the advantage is lost.
If you had one combination or a bunch set up exactly the same running high speed flatland you could make money where others were battling to survive just on the savings you could achieve.
These type of devices are obviously not the answer to all situations.

 

http://www.google.com/patents?id=NmIQAgAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false

 

That's what Airtabs do, using horizontal vortices.

From Tapatalk- for when you're really addicted.

 

i've got air tabs and love them

 

well having seen a few trucks with the 'teeth' on the front grille and one of those flaps or big cones on the back.. there ought to be a certain decal for the rear of the package..

 

Anything to improve arrodymics is money in ur pocket.I like the trailer fairings, more mpg and truck handles much better.But,they can be a problem in deep snow.

 

The big issue is that some states are being picky and writting tickets for over length.... greater than 53'.. I know a couple of drivers are fighting the tickets not sure of what the out comes is/was...

 

There is a specific reg written exempting these devices from length measurement on any STAA route.

 

We are paid so cheaply that we put those wings on the trailers because we are trying to learn how to fly