Truck Wings - Do They Really Save Fuel ?

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N5IBM

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Just checking with any of you that have actually installed a truck wing pulling your 5th wheel, and if it increased your fuel economy.

Thanks, Russell - Orlando, FL
 

Ron

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I have no first hand knowledge. However, I met a guy in Brenda that had one the one year but didn't the next year.  I was there when another 5er owner asked what happend to the wing on the truck and his answer was that using it the year before and comparing to the previous year it didn't make any difference other than it was just something else that required attending to when he arrived in Brenda.
 

Carl L

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Evidently they work for commercial, semi-trailer hauling trucks.  See the test results at http://www.freightwing.com/.  Given that it is a manufacturers site and they paid for the testing, there is little reason to doubt the results.  Certainly a lot of trucking businesses spend their money on the product.

Anecdotally, I can really feel the difference in shock wave and turbulence between a winged and faired truck passing my trailer and one without the equipment.  The protected truck's shock wave is minuscule, the unprotected one has a pronounced shockwave.  It is generating that shockwave that costs the fuel mileage and is cured by the wing.

In fact, the worst offenders on the road for shockwave are not the semi-trailers but the panel vans, buses, and motorhomes.  OTOH, 5ers do not seem to be major offenders in the shock wave department -- but then only the biggest 5ers come near a semi in frontal area.

 

Gary RV_Wizard

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The fly in the ointment is that the "wing" has to be tuned to the aerodynamics of the tow vehicle and trailer.  The chances of getting any benefit froma one-size-fits-all wing added to your particular truck and trailer are just about nil.  Even if the wing mount is adjustable.  Without some wind tunnel analysis, you have no idea what you are doing to the airflow.
 

w5blt

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I have unsuccessfully searched for about an hour for what I'm about to describe. This thing that I'm talking about is an "air disruptor". It's plastic, about 4" square with specific molding on it. It is normally used on the trailers for big rigs. The purpose is to disrupt and defuse the air that causes the "drag" on the trailer. Thus, increasing the MPG. Those that have used this on RV's and 5ers (gee, I wish I could find that URL), it has a dual purpose. First, it decreases the drag on the RV/5er and second, it drastically reduces the dirt and road grime that gets on the back window.

I would really like to have found this web site so I could refer everyone to. If I find it, I'll post it. Sorry. However, maybe someone can help me out here.

Bob
 

Tom

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I can't imagine a 4" (4 inch) deflector having any measurable impact on drag, fuel economy or anything else. Do you mean a 4 foot deflector?
 

Phil

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Tom said:
I can't imagine a 4" (4 inch) deflector having any measurable impact on drag, fuel economy or anything else. Do you mean a 4 foot deflector?

Tom,

Roll the window down and stick your hand out doing 60 MPH and you will get a good "feel" of what wind drag on a 4" deflector is.  ;D

Phil
 

w5blt

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Phew! I finally found it. Check out this link about AirTabls http://www.airtab.com/

By the way, you don't just use one. You may be using 50-100 depending on your application. There's a pretty cool video on that web site that shows exactly how they operate and perform.

Ya thought I was nuts, huh?
 

Tom

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Phil

Translate that to hp, mpg, or whatever and it's negligible.
 

Tom

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There's a big difference between one 4" deflector and 50-100 of them  :)  I can't imaging attaching all those things to my RV. If nothing else, it would look quite ugly.
 

w5blt

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Tom said:
There's a big difference between one 4" deflector and 50-100 of them? :)? I can't imaging attaching all those things to my RV. If nothing else, it would look quite ugly.

I don't believe that I said that you only needed one of them. As far as looking ugly, they can be painted the same color as your rig. But, the bottom line is improving your MPG.
 

Tom

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w5blt said:
I don't believe that I said that you only needed one of them.

Oops Bob, didn't mean to step on toes although my message wasn't specifically directed to you. But, for the heck of it, I looked back at what your message contained:

This thing that I'm talking about is an "air disruptor". It's plastic, about 4" square with specific molding on it.

Nothing in those comments suggested more than one deflector.

I'll skip attaching them to my coach and painting them, partly because I suspect they would depress the resale value. Doesn't mean I don't think they'd work.

Thanks for sharing this gadget with us.
 

BernieD

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Tom said:
Translate that to hp, mpg, or whatever and it's negligible.

Tom

I was delivering a PressurePro system to a customer. He had a Foretravel towing a Jeep GC and both units had all of these deflectors on them. Turns out he is a distributor for them, a friend of his developed them. I believe he had around 100 on the coach, including the A/C covers and other air grabbers on the roof. The deflectors were mounted on the rear of the coach, about 4" apart going up the sides and across the roof. A similar setup was on the Jeep. The deflectors are clear plastic tho he had a few of them painted. They were noticeable, but not obtrusive. He also claim the airflow kept his rear camera and Jeep rear window much cleaner.

IIRC, he indicated that he got between 1-2 mile increase in fuel economy with the deflectors installed. I wouldn't call that negligible.
 

Tom

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Thanks for the report Bernie.

BernieD said:
IIRC, he indicated that he got between 1-2 mile increase in fuel economy with the deflectors installed. I wouldn't call that negligible.

My "negligible" comment was made when I thought we were talking about only one 4" deflector (or just one hand stuck out the window). I kept thinking about the things some 5th wheel owners have on top of their truck to deflect air/reduce wind resistance - same concept as many of the truckers use to decrease drag, which was why I asked if 4" really meant 4'.  It wasn't until I saw the picture that I had a HFWPOH moment and realized what "it" really was.

I have no reason to doubt the claims of improved fuel economy, nor do I have any data to support it. Last night in bed I was mentally drawing an analogy with an anechoic chamber which has lots of surfaces protruding into the room to intercept air  (sound) movement, although in the latter case the materials are designed for absorption rather than deflection. Not being an air or acoustics engineer, my completely non-engineering take on it (before I finally fell alseep) was "this probably works".

I doubt I'd add them to my coach though, painted or otherwise. OTOH if fuel prices achieve new highs maybe some of the RV manufacturers will start offering them as an option. Hopefully the inventor has applied for a patent and he could do well out of it.
 

BernieD

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Tom

My customer said that his fuel economy was based on refuels over a long period of time before and after the installation. Of course, if you use Rolling Stock, that is a very easy comparison to make  ;)

When you drive your big box down the road, you create a virtual vacuum behind the coach. The deflectors smooth out the air and move it around the vacuum improving your aerodynamics. I do believe the shape is patented.
 

Ron

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IIRC, he indicated that he got between 1-2 mile increase in fuel economy with the deflectors installed. I wouldn't call that negligible.

Of course a distributor would get that much improvement. ?Now what would really be interesting is to know what the rest of us would really get for improvement. ?I didn't see any mention of wind tunnel tests to back up their claims. ?It is easy to build and sell almost anything and claim it improves mileage but without documented test results it is all hype.

 

Tom

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The deflectors smooth out the air and move it around the vacuum improving your aerodynamics.

Ah yes, I recall seeing video of wind tunnel tests and computer modelling of air flow for spoilers on cars. It would be interesting to see the same tests &/or models for these deflectors. Come to think of it, I've not seen any such tests or models on RVs as-is.
 

Ned

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There are some photos of wind tunnel tests on the web site.  I can't vouch for the validity of them.
 

Ron

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Airflows and airflow behavior vary greatly depending on the surface, shape and length of an object. What one would visualize as a workable solution doesn't always work. ?without intensive wind tunnel test with smoke to study airflow patterns one cannot determine how an add feature will affect airflow or if it would have positive or negative results. ?Change a variable such length, shape, or protrusion and a lot can change. ?Such a device could work in one situation but cause negative turbulence in another. ? Without valid test results, which if they had them I think they would be publishing them, it is all like playing poker or a guessing game.

Show me the test results. :D ;D
 

Tom

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Ned said:
There are some photos of wind tunnel tests on the web site.

I must have missed them. All I saw were some "computer simulations" in the video and a couple of animated gif images. Like Ron, I'd like to see the data, including test conditions, etc. The web site says it was tested in a NASA wind tunnel. I've lost my connection with someone who used to work there; he might have some knowledge or witnessed the tests.
 

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