LouLawrence
Traveling the US fulltime since 2000.
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JimK-NY wrote:LouLawrence wrote:JimK-NY wrote:LouLawrence wrote:If anyone thinks that adding an air deflector DOES NOT help is delusional. Air going over a trailer vs. slamming into the top of the trailer is a real thing. How much? Can't say, but it's a reality.
How much? Got any data?
It's been working for tractor trailer drivers for years.
Again, where is the data? I could not find results of any studies.
I could actually care less if you can't find the studies. If you don't believe it, don't do it. I doubt there are any truckers anywhere who have taken their wind deflectors off.
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fj12ryder
Platte City, MO
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"I could actually care less if you can't find the studies. If you don't believe it, don't do it. I doubt there are any truckers anywhere who have taken their wind deflectors off."
There's a very big difference between the placement of semi wind deflectors and RV wind deflectors, in fact it can be measure in feet. If you don't get the deflector close enough to the trailer, there isn't going to be much benefit. Of course if everyone agreed that they worked as well as you're suggesting, there wouldn't be a semi out there that didn't have them. But there are lots of them, so there must be a lot of delusional people out there. ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/smile.gif "smile")
And .5 mpg increase can be put down to many things, not the least being a unconscious desire to make sure the mileage is better, i.e., backing off just little bit, a little less acceleration, many things can show .5 mpg increase. A person could perhaps be delusional to think it has to be the results of a wind deflector. Sometimes the data is worked with to support the theory, rather than vice versa.
Howard and Peggy
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dodge guy
Bartlett IL
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fj12ryder wrote:"I could actually care less if you can't find the studies. If you don't believe it, don't do it. I doubt there are any truckers anywhere who have taken their wind deflectors off."
There's a very big difference between the placement of semi wind deflectors and RV wind deflectors, in fact it can be measure in feet. If you don't get the deflector close enough to the trailer, there isn't going to be much benefit. Of course if everyone agreed that they worked as well as you're suggesting, there wouldn't be a semi out there that didn't have them. But there are lots of them, so there must be a lot of delusional people out there.
And .5 mpg increase can be put down to many things, not the least being a unconscious desire to make sure the mileage is better, i.e., backing off just little bit, a little less acceleration, many things can show .5 mpg increase. A person could perhaps be delusional to think it has to be the results of a wind deflector. Sometimes the data is worked with to support the theory, rather than vice versa.
The lengths people will go through to make their point is ridiculous. Everyone saying that they have used one and got better mileage and you still don’t like the answer. Sorry, but they can and do work! Try it for yourself and see. But stop trying to make yourself believe it can’t happen!
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fj12ryder
Platte City, MO
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Actually for RV's I think there are more studies that say they don't work than there are studies that say they do. So stop trying to make yourself believe it can happen!
You think they work, and I think they don't. We'll just have to agree to disagree.
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maurice-r
central indiana
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Admittedly, a Chevy Express van gets poor gas milage, but we enjoy our van. Our adult kids keep trying to get us to buy an SUV like them, but for some reason, they still ride with us in our 15 passenger van!
Our family did one trip with no deflector, and saw the fuel economy drop in half. I did some google searching, including here on RV.net. I saw a lot of negative comments, but a few positive. So I figured, what the hey, its just a hobby and my time; I'll try something. For us, it worked.
I was not and still am not prepared to do scientific studies. I am not selling any plans, just basically giving away my idea and example. If I have everything fastened down so that I do not present a hazard to someone else nor bring attention to our fine dedicated Highway Patrol, then why be so adamant that "it does not work"?
Thank you for allowing me a place to post my idea!
Maurice and Brenda
Franklin, IN
2001 Chevy 15 passenger and 1999 Venture pop-up
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JimK-NY
NY
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Before going through the effort and expense, I would like to know if an air deflector was worth it. This discussion reminds me of the air whistles that are supposed to help avoid hitting deer. There have been lots and lots of studies that show no effect, but plenty of people still use them and believe they work.
I have done many tens of thousands of miles driving my RV and have recorded every drop of fuel I have used. My fuel mileage has been highly variable due to road delays and conditions, hills, speed, ambient temperature, wind speed and direction and who know what other factors. I would never notice a difference of a half mpg due to a deflector. It would take a controlled experiment with an accurate fuel consumption detector.
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LouLawrence
Traveling the US fulltime since 2000.
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If it only kept the bugs off the front of the trailer it would be worth the effort with no downside at all.
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valhalla360
No paticular place.
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dodge guy wrote: Everyone saying that they have used one and got better mileage and you still don’t like the answer.
But not "everyone" is saying that. I know a couple of guys who added them...then a year or so later they got rid of them because it was more hassle mounting and demounting with no improved MPG to show for it.
As stated before, there is a huge amount of variability between RV configuarations and then claims with no attempt at consistent testing...if everyone got noticably better MPG, I'm sure you would see 90% of towing trucks with air deflectors...yet the exact opposite is true.
On the other hand near 100% of semis pulling standard box trailers use them. You can bet the trucking manufacturers and haul companies have tested and confirmed how to implement to get the maximum benefit but unlike RVs, it's a very standardized configuration, so easy to apply to the next truck they buy.
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maurice-r
central indiana
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I respect you guys who have driven tens of thousands of miles! I had not seen any air deflectors that were as gradual as the one I made. I wondered how effective the short but sharp angle style is. Such as two pictures that have been posted in this thread.
If I may ask for clarification? Of the comments of little milage difference, (both your experience and from hearing others report) are most of the air deflectors of the short length and sharp angles?
Could it be possible that a long shallow angle deflector might help milage better than a short sharp angle?
Our family members also drove a Ford F150 pulling a car hauler empty except for a small cargo trailer ON the car hauler - so top of small cargo stuck up at the 9' mark. His fuel milage was much lower than with no trailers. (I had offered to make a quick "camper shell-air defelctor" out of osb ply before we left but he said his bed cover prevented that.) He got better milage on the eastbound trip when he pulled the car hauler with a kia sedan on it and another family member drove his own F150 pulling the samll cargo.
Again I say, all of my information is from the dashboard computer, so it is not scientific.
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valhalla360
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maurice-r wrote:I respect you guys who have driven tens of thousands of miles! I had not seen any air deflectors that were as gradual as the one I made. I wondered how effective the short but sharp angle style is. Such as two pictures that have been posted in this thread.
If I may ask for clarification? Of the comments of little milage difference, (both your experience and from hearing others report) are most of the air deflectors of the short length and sharp angles?
Could it be possible that a long shallow angle deflector might help milage better than a short sharp angle?
Our family members also drove a Ford F150 pulling a car hauler empty except for a small cargo trailer ON the car hauler - so top of small cargo stuck up at the 9' mark. His fuel milage was much lower than with no trailers. (I had offered to make a quick "camper shell-air defelctor" out of osb ply before we left but he said his bed cover prevented that.) He got better milage on the eastbound trip when he pulled the car hauler with a kia sedan on it and another family member drove his own F150 pulling the samll cargo.
Again I say, all of my information is from the dashboard computer, so it is not scientific.
The problem is it takes some science and testing to get something proven and effective (while not perfect, our dash readout matches pretty well when we check against hand calculations). A smooth transition is important but the biggest trick is getting the back of the wing as close as possible to the front of the trailer matching the height of the trailer front. A big gap or a drop after the cab (such as with a pickup) results in difficult to predict results.
Interestingly having done 5 east/west cross country trips over the last dozen years with different rigs, I've found eastbound typically gets better fuel economy looking at my records. When I look at the individual days runs, it correlates well with the winds conditions (most common winds in the lower 48 are from west to east). For example on the current trip we are just finishing up, we averaged 9.1MPG westbound and are at 9.9MPG eastbound. Same rig, same driving speed/style and similar terrain.
There is no question that aerodynamics can help but randomly sticking a wing on will result in random results.
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