Anyone have any experiance using airtabs on their motorhome? Thank You.

What are airtabs?

quote:

airtabs

http://www.airtab.com/

Most websites that I found say "snake oil"

I figure if something this simple would save you
%4-6 on fuel that manufacturers would incorporate it from the factory.

They are air deflectors for trucks and RV's. Supposed to increase fuel milage, enhance handling and keep the back of the vehicle cleaner. You can check them out on airtabs.com.

quote:

Most websites that I found say "snake oil"

Now would the "snake oil" be the concept of vortex generators? "Most websites", a great reference standard, would say that vortex generators are a well proven technology used in the aviation industry for years.

Or would the "snake oil" be in the application of vortex generators in the trucking industry?
Which leads us to

quote:

I figure if something this simple would save you %4-6 on fuel that manufacturers would incorporate it from the factory.

This would be relevant to the trucking industry that first implemented the streamlining changes recommended by government research done in the 1950's with the release of the 1998 Volvo? That same industry that is finally addressing frontal streamliningwith the other brands?

Without having to enter everything again, go to post AirTab for Better Mileage

The slowness of the trucking industry in implementing new technology doesn't negate the technology.

From an RV prospective, the use of vortex generators (AirTabs) makes a lot of sense. Whether a motorhome of a trailer, there is a big low-pressure area behind the RV that causes drag and sucks up a lot of road dust depositing it on the RV.

I would say that you need to refer to better

quote:

Most websites

Let's see, if I were a RV manufacturer and could get an almost free, and could prove 4-6% fuel milage increase in this day and time, why would I not do it??? Although my coach gets about 8 mpg and 5% would increase that to 8.4 mpg, that is within the range of what I get as a variable already. The only ones I've seen that really support these things are the ones that have spent the money and then make these wild claims of huge increases. I've never noticed a study by an UNBIASED source on these things. You can get a much larger increase in fuel mailage by slowing down 5 mph in your driving and it won't cost a penny. Go figure!!

Perhaps someone can get Myth Busters to check them out?

I agree with Kirk that I would like an independent group like Myth Busters or Consumers Report to test the AirTabs.

But to discount the concept because

quote:

Let's see, if I were a RV manufacturer and could get an almost free, and could prove 4-6% fuel mileage increase in this day and time, why would I not do it???

Well we all have seen that an extra $150-$200 dollars to make sense in an RV is often overlooked by the manufacturers. And until this year, a few tenths of a MPG had no marketing value. The manufacturers would spend that money on something glitzy first.

This is a serious subject in the trucking industry, now. Articles like Article 1, Article 2, Article 3, Article 4, and =http://trailer-bodybuilders.com/trailer-oem/aerodynamic_breakthrough_rolling_road_testing/]Article 5[/URL] all speak to the efforts and some of the various aerodynamic improvements that can be practical for a commercial truck.

Why hasn't AirTabs made a major inroads to the trucking industry. Who knows. The reason most of the readers on this forum know the name is because of RVTV. I know from prior experience in trying to sell trucking companies on other technologies, they are a hard sell even with great return-on-investment values.

I know that I can benefit from some aerodynamic improvements. Given our average annual mileage, a .25 mpg improvement would pay for a set of AirTabs in one year. I just have to balance that with other things that might give a similar cost payback improvement.

Here is my unbiased experience with AirTabs.

I have a 2008 - 38' Cross Country pusher. 340 HP Cummins.
I tow a 26' stacker car trailer that hauls two drag cars, golf cart, etc. weight is 16800 loaded and it sticks above the motorhome roof by about 14".

Best mileage in three 700 mile trips was 5.7 to 5.8 mpg running about 60-65 on Interstate and 60 on State highways. Always in 5th gear as it would not pull or hold 6th gear.

I installed Airtabs on the trailer at the rear. I built a 14" flat wind deflector, set at 40 degrees and bolted it to the roof of the coach. I installed Airtabs along the top edge of the air deflector to accelerate air in a straighter line.

I have made one 500 mile trip in normal conditions. Results--OH YES!
1. Avg MPG for 513 miles 7.7 mpg. (about 30% better.)
2. It stays in 6th gear on everything but longer grades. It isn't like a 400 HP but it is a heck of a lot closer to feeling like one.
3. When a tractor trailer pulls up on the rear of my trailer it no longer pushes the trailer over 6 or 8" and this means almost no sway.
4. I am going to install them on the coach next week and see if I can get the air straightened out between the coach and the front of the trailer. I would guess I'll find a even more of a gain then.

Would I recommend Airtabs...........absolutely, Are they a cure all for everyone, probably not. But at $4.50 a gallon and 5 to 8 mpg you can do your own math. I would guess he will not be able to make them fast enough when the racers I know, who tow with motor homes, read my tech story in the magazine I write for, www.dragracingonline.com in the next month or so.

I DO NOT see sound engineering as Snake Oil. Now if it's a magnet on your fuel line, or a fuel additive....that is closer to Snake Oil.

The motor home industry has completely ignored aerodynamics for decades. Too bad, there will be very few manufacturers left pretty soon.

Jok Nicholson
'08 Coachman Cross Country DS38
340HP 6.7L Cummins

Thanks for the info. I think I've convinced myself that they would be worth the $200 or so investment.

Cleaning up the roofline by eliminating the clutter of roof mounted air conditioners, MaxxAir vent covers, etc. and improving the airlfow underneath the rig by enclosing the chassis with a smooth pan would probably improve mileage as much, if not more, than these little tabs.

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Originally posted by Lou Schneider:
Cleaning up the roofline by eliminating the clutter of roof mounted air conditioners, MaxxAir vent covers, etc. and improving the airlfow underneath the rig by enclosing the chassis with a smooth pan would probably improve mileage as much, if not more, than these little tabs.

That is a lot easier said then done on a coach you already own ...Agreed that makes a lot of sense for the OEMs though. Trailertoad1, By installing the tabs at the same time you installed the roof deflector, how can you be sure which contributed to the MPG gain the most? It would be interesting to see what the tabs do on their own .

With all due respect to Trailertoad1, your unbiased report, while interesting, is meaningless. It is what is known as anecdotal evidence. There are way too many variables involved for any valid conclusions to be drawn from your results. The only way these devices could be properly tested would be in a controlled environment like a wind tunnel or in a very long term road test with controls, such as could be done by a trucking firm with multiple rigs and thousands upon thousands of miles. I know trucking firms are exploring various methods of streamlining their vehicles, but none I have seen are as simple as gluing these tabs on their trailers. If it were that simple, they would all be doing it.

A lot of the roof of RVs has stale air on it when in motion, particularly when moving fast, The relatively blunt front end creates an envelope that leaves the air sitting on the roof as a high pressure area with relatively little surface flow.

For this reason, I would wonder if the AirTabs would make some kind of significant difference mounted on the face of the front cap along the top edge?

Yes, I wonder about the deflector that was added, too, and just how much of a difference that might have made, alone.

No question that anything that prevents a big vacuum behind any unit is going to help MPG, it is a bigger question about what resistance frontal loads present.

I have long wondered if a wasp-waist connection between a tow vehicle and a 5ver would greatly help the overall slickness. Its what they have long looked at in the aerodynamics industry on fast planes and even had a line of commercial carrier planes designed like this about 15 years ago, IIRC.

Still, slicker is better.. just need to know where it makes the most sense and that is often not the places that are intuitively the most likely places.

One example of this is the benefit of rounded corners and edges over the more typical sharper edges of box trucks, vans and the like. A study many years ago showed a huge reduction in drag just by turning the "Winnebago edges" of motorhomes into a curved edge with a minimum of a 2" radius. Companies like SportsCoach, made this part of the frame and got some amazing mpg improvements on the same chassis that many other MH makers were using at the time.

Overall length can have a huge affect, too, depending on where the envelope collapses onto the box. My 24' Winnebago got much worse gas mileage than my 27' with the same engine, transmission and differential.. and th3 27' was heavier. But, putting a pinto behind the 24' improved the gas mileage a lot. Putting it behind the 27' made no difference. These differences had to do with the length of the boxes only.

I wonder what a front air dam and side skirts would do to MPG ? Emery, I found it interesting that you obtained better MPG with the toad then without, even with the heavier unit, the same as adding a boat tail to the Winnebago I guess.