Has anybody ever seen anything like this? Does it work?

Home : Airtab

 

I believe I know a member (Aerocell4x4) that has them on his rig. I'll shoot him a message and ask him to stop by here. It won't be until later though as he is only online late afternoon into the evening.

 

They don't do anything to improve fuel economy. I did my graduate research on Commercial truck aerodynamics. I'm familiar with many of the devices out there. These don't help.

 

I know we had vortx generators underneath the wings and horizontal stabilizers on the venerable USAF's KC-135 Stratotanker. They were for stability. V/r Les

 

Hello there 5280
(Secret agent man, they've given you a number and taken away your name ...)

Yes, I have AirTabs on my cutaway chassis van.

Pictures are in my Gallery 2006 Ford Econoline 4x4 - Aerocell - Post Quigley 4x4

As I recall, AirTabs claims a one to two mpg increase for an eighteen-wheeler, which if it gets seven to eight mpg to begin with that would be a significant improvement.

I bought them to dress-up my van.

I might have gotten a one mpg improvement out of them, but then the improvement might have come from the engine breaking-in.

When I bought the truck with three thousand miles on it I got about 14+ mpg, after the AirTabs I am getting about 16 mpg.

I drive mostly interstate in cruise control at 55mph along relatively flat coastal highway, even on the back roads I'll use cruise control down to 30 mph.

The most noticeable benefit of the AirTabs for me is a marked reduction in vehicle sway when buses & 18-wheelers overtake me, I used to have to actively steer as the van was buffeted, and now its like they are not there.

The back of my van doesn't get as grimy as big box trucks do.

So AirTab's claim that their vortex generators modify the air flow behind a truck seems to hold true.

 

I have an FAA Mechanic's certificate with the Airframe & Powerplant ratings so I know something about those vortex generators.

Vortex generators are applied to areas of the aircraft where there is a need to 'hold' the air flow to the surface of the aircraft.

Most people understand that the airplane 'stalls' when the airflow separates from the surface of the wing and the wing thus looses lift.

What they might not realize is that the air flow will also separate from other surfaces of the aircraft, and that separation renders whatever is 'behind' it (down wind) ineffective, such as a flap, elevator or rudder.

So depending on the aircraft, when the flaps are deployed you might see a row of vortex generators appear as the flaps approach maximum extension, their downward deflection is such that the air doesn't, of its own, flow smoothly off the wing and down the surface of the flap.

The vortex generators induce the air flow to cling to the surface of the aircraft in these conditions thus enabling greater useful flap extension.

You'll notice that the tail surfaces have them too, and on propeller driven aircraft only asymetrically and that is due to the corkscrew airflow from the propeller down the length of the fuselage. With the airplane in certain attitudes (not to be confused with altitude) one side of a stabilizer will have a good flow of air across it, while its other side is relatively calm, so vortex generators are placed on that 'calm' side to keep the airflow 'attached' to that surface and thus the elevator/ rudder remains effective when deflected toward that otherwise 'calm' side.

On a truck / van the vortex generators have the effect of streamlining the back of the 'brick'. Think of the Space Shuttle being carried on the back of the 747, NASA put a cone over the rocket engines to reduce the aerodynamic drag of the Shuttle. Also those Car-Carriers that take your car down south for the winter as you fly there, they have a similar fairing at the back of their trailers.

The AirTabs are intended to create that same effect of streamlining, think of those down draft air curtains that keep the bugs from flying through open warehouse doors. The AirTabs are intended to create a wall of vortexes that converge behind the truck and which then act to guide the surrounding airflow smoothly past the back of the truck.

 

And now I'll go back to the Connecticut Chapter and lurk as usual.

You can blame Greg for asking me to

 

I have them on the trailing edge of my roof. Have not noticed any improvement to fuel mileage. Took like 13 or 14 of them to span the width of the cab. Now that they are on there I am going to leave them so it does not peel the clear coat off. They do stick good.


If they really worked all the 18 wheelers would use them. 1 MPG or even .5 MPG times the hundreds of thousands of miles would be a big saving.