It may just be me looking thru old eyes, but in looking at the pic of the airflow and comparing it to the way they are installed in the first post, arent the top ones on backwards?
They look OK to me. The pointed end of the AirTabs should be aimed to the rear, or towards the direction of the airflow, and the ones on this application seem to be doing that.
We were talking to an Air Tab representative at an RV show just after getting our Outlook. He suggested driving the MH for a year before installing the air tabs, order to fully realize the difference. Other claims are a cleaning back end and camera operation, especially in rainy weather. Better handling in crosswinds and passing trucks, as well as an increase in fuel mileage. The air tab says fuel mileage should increase between 2% and 12%. At 10mpg a 10% increase would only be 1mpg.
I am reluctant to get them, mainly because of the MH design, slide out trim very close to rear on one side and awning arms on the other side. I am not sure how they would work.
If I could get an extra 2.2 MPG on our motor home, I would place my order first thing tomorrow, but the company advertises a 6.06% improvement and that would give me an extra .5 MPG increase, which is good! Bagman.
Back in the 80s we had a Blazer, and the back window would get dirty quick. I suspect the flat back was creating a low pressure air area, sucking up dirt and water to fill the void behind the vehicle at highway speeds. So I installed a chrome wing 4" Hi by 50" wide or so, on the top right at the back. These were sold in auto stores back then.
It sloped up to the front at about a 45 deg angle, and it did scope air in and force it down into the low pressure area behind the truck, and keep the back window cleaner longer.
I did not run any test on mileage, but I would think having them on three sides would make some difference, in braking the slight vacuum behind any big flat back ended vehicle at freeway speed, and should increase mileage some.
2001 27' Four Winds Class-C E-450 V-10.
Buick Park Ave Ultra, Ford Ranger PU, JD 500 backhoe.
1941 Farm All "A"
Polishnurse wrote: Sounds like the Myth busters should run a test on these.
Mythbusters is great TV but some of their science is flaky and I've never seen them do anything with the rigor that this test would require. You would want to see the work done by some graduate students at a university that has a strong automotive program.
Now that I think about it there is a way to do the test fairly easily but it would make boring TV and I doubt that MB would touch it. You would need two "identical" motorhomes and run them around a test track for several 100 mile tests to get a good idea of how their mpg results compare. Then put the airtabs on one of them and repeat the tests. You'd run both at the same time on the same track, half a lap apart, to make the environmental and road conditions the same for both. If the airtabs work the difference should show up.
Unfortunately for owners you can't run this test by yourself since differences in weather, road, traffic, and fuel pumps will bury the result in measurement noise. But if you have a friend who has a fairly similar MH who is willing to make the same trips at the same time stopping at the same stations using the same pumps and fill technique you could run the test fairly well. Make a few trips together to get comparative data, put tabs on one MH, make the same trips together again and compare the results.
Ken
Mythbusters did do a similar test......whether running a pickup with the tailgate up or down (or removed, I can't remember) would yield better fuel economy. The results were interesting. Tailgate up won. They also did a test in a "water tunnel" with dye to show what was happening and confirmed it with the truck manufacturer.
The back to back test with airtabs in same conditions or running may vehicles with and without to get a good big data sample would have to be done to get good results. With the current cost of fuel one would expect that vehicle manufacturers or fleet owners would be jumping all over it if there was something there to be had economy wise.
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