Gas mileage and air deflectors for vans - Fiberglass RV


View Poll Results: Will a deflector make much difference?
Yes, it will help 0 0%
Yes, it might help, but not much. 0 0%
No, I tried it and it was not worth the cost or effort 0 0%
Yes, but your driving habits are more important than the deflector. 2 100.00%
Multiple Choice Poll. Voters: 2. You may not vote on this poll

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Old 08-30-2019, 09:19 PM   #1
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Name: Ron
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Gas mileage and air deflectors for vans

I tow my 14' camper with a 2000 Dodge Grand Caravan. I am considering attaching a panel set at a 40 degree angle to the roof of my van at the back to deflect air over my camper, which is about 2-3 feet higher than my van roof. Will this improve my gas mileage, and is it worth the effort? I have the materials to make something with a deflector panel about 4 feet wide and about 20 inches tall. This would attach to the stock roof rack.
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Old 08-30-2019, 09:30 PM   #2
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I think you need access to a wind tunnel to work out all the parameters. Without information, you may make things better or worse. Maybe you would improve gas mileage and destroy handling.
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Old 08-30-2019, 11:01 PM   #3
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Just a guess, as without a wind tunnel it seems impossible to say, but that sounds like a lot of download on the panel and the rack, a lot of buffeting sound in the van, and a lot of turbulence between the van and the trailer. All of that sounds like worse mileage and some work to achieve it.

One advantage though, with all the buffeting sound inside the van, if the panel gets torn off by wind resistance, you'll know it right away by the quiet.

Seriously though, how much improvement are you expecting? Even if it seems to work, I'd bet it's not measurable. And the only time it might be is at highway speed. Why not just slow down 5 MPH and get a much larger benefit? Then you won't have to build the rack and you won't have to push on the throttle so hard.
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Old 08-30-2019, 11:42 PM   #4
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The poll at the top has three "Yes" options and one "No" option.
Another pointless poll.
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Old 08-31-2019, 03:01 AM   #5
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If it's the right shape/design, it should get you a small-but-not-zero improvement in gas mileage. The wrong shape could easily tip it over to worse, though. It's pretty hard to guess/generalize whether it'll help or not. Realistically, the only way to find out is to test it. I'd be surprised if it made as much of a difference as driving smoothly and slowly, though.

Also, keep in mind that any wind resistance improvement is also going to mean a bit more braking required on steep downgrades.
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Old 08-31-2019, 06:48 AM   #6
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I have used a wind deflector on my truck roof with several trailers. My deflector is only about 16" tall. It does not need to be as high as your trailer. It just kicks up the air flow over the trailer. My deflector is adjustable. I adjust it so very few bugs hit the front of the trailer. My assessment is it does not help gas mileage that much but it keeps the majority of bugs off the front of your trailer. That can be a good thing during love bug season in Fl.
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Old 09-01-2019, 05:36 AM   #7
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We have already used an adjustable baffle on our Dodge Caravan in about 2005, with a trailer Trillium Jubilee 1980.
Without the deflector when our speed reached 90 km / hr (55 mph) and more we felt a movement back and forth in the caravan.
I found and installed an adjustable baffle.
After several tries I had to install the baffle the furthest possible rear of the caravan, to make completely disappear the unpleasant movement felt.
For adjustment in degrees, each vehicle and trailer is different.
On the Internet I had read that to know if we had the right angle, we would stick a ribbon in the top of the deflector and the ribbon should float horizontally when we reached the desired speed. Not easy to check ...
The other method suggested by my parts supplier is to randomly adjust the deflector, until the movement disappears and as Eddie wrote, that the insects had dimunied much on the top of the trailer. It's this method that worked for us.
When I replaced the Caravan with a Dodge Journey, without a deflector I did not feel the movement of back and forth felt with the Caravan. So not installed.
I have never calculated to measure the difference in gas with or without a deflector.
Each vehicle and trailer will react differently, in my experience.
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Old 09-01-2019, 10:33 AM   #8
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The commercial truckers have vortex generators available and measured improvements after much "testing" average the max improvement of about 1 - 3 %.
The idea is to generate vortexes that leave the rear of the TV and help the air bypass the area between is and the trailer.
They also install them at the rear of the trailer to smooth out the airflow behind it.
All in all for our small trailers I wonder if it is worth bothering with.
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Old 09-01-2019, 10:48 AM   #9
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Quote:
Originally Posted by redbarron55 View Post
..
All in all for our small trailers I wonder if it is worth bothering with.
Maybe if your tug burned 4-5 times as much fuel and you towed your trailer as many miles as a commercial semi-truck does (roughly 45,000 on average)... but most of us only put 1,000 to 2,000 on each year on our trailer (and truly this time.. YMMV! )
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Old 09-01-2019, 03:29 PM   #10
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Quote:
Originally Posted by gordon2 View Post
Maybe if your tug burned 4-5 times as much fuel and you towed your trailer as many miles as a commercial semi-truck does (roughly 45,000 on average)... but most of us only put 1,000 to 2,000 on each year on our trailer (and truly this time.. YMMV! )
On my Dodge Caravan, I had installed the deflector only to remove the discomfort of turbulence at 55 mph and more, not for fuel economy, I never calculated it.
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Old 09-01-2019, 07:37 PM   #11
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You didn't mention what trailer you have so it's hard to imagine its shape. I would think something shaped like an Airstream or a Scamp with a wall installed AC would be very difficult to easily improve upon a van's mpg.
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Old 09-01-2019, 07:42 PM   #12
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You didn't mention what trailer you have so it's hard to imagine

You don't say who you are responding to so it's anybody's guess. However, if you look at the profile under the poster's name, you might find info about trailer and tow. Or not.
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Old 09-01-2019, 08:03 PM   #13
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Did you look at the originator's profile? There's no trailer type noted.
Quote:
Originally Posted by Glenn Baglo View Post
You don't say who you are responding to so it's anybody's guess. However, if you look at the profile under the poster's name, you might find info about trailer and tow. Or not.
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Old 09-01-2019, 09:05 PM   #14
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Did you look at the originator's profile? There's no trailer type noted.

I still don't know who the OP is. Who are you referring to? Which post?
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Old 09-01-2019, 09:14 PM   #15
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Originally Posted by Glenn Baglo View Post
I still don't know who the OP is. Who are you referring to? Which post?
Glenn, OP = Original Poster. See post #1
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Old 09-01-2019, 09:21 PM   #16
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Quote:
Originally Posted by ibupnorth View Post
You didn't mention what trailer you have so it's hard to imagine its shape. I would think something shaped like an Airstream or a Scamp with a wall installed AC would be very difficult to easily improve upon a van's mpg.

This is the post I was referring to, which I quoted, so you would know what I was referring to.
Prior to ibupnorth's post ( above ) there are three others who posted on topic. I don't know that ipupnorth's post is a response to one of the three, or which one, or one posted much earlier.

People may think that they are responding to the last post they see, but others may respond first, which leads to confusion.
To clarify, I am responding to Donna Dee's post, since it's quite possible others have responded in the time it took to write this.
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Old 09-01-2019, 09:24 PM   #17
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Quote:
Originally Posted by Donna D. View Post
Glenn, OP = Original Poster. See post #1

There are six other forum members who responded after #1.
To quote: "You didn't mention what trailer you have".
Who is "You"? Where does it say OP #1?
I'm suggesting that it always helps to quote at least part of the post you are referring to, or to name the person you are responding to.
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Old 09-01-2019, 09:44 PM   #18
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Originally Posted by Glenn Baglo View Post

"People may think that they are responding to"..........
Glen, thanks for being concerned about me and what I might think, but I wasn't confused about the ongoing discussion. Responses should be assumed to be directed toward the OP unless otherwise specified. Doncha think?
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Old 09-01-2019, 09:49 PM   #19
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Are you talking to me?
Two 'n's.
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Old 09-01-2019, 10:05 PM   #20
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Quote:
Originally Posted by Glenn Baglo View Post
Are you talking to me?
Two 'n's.
"Name: Glenn ( second 'n' is silent )"

Sorry, I left out the first n, instead of the second n. My bad.
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