Wind Deflectors for Towing

[lamborghinifan]

Just wondering has anyone had any experience with using any sort of wind deflector on the top of their car when towing a trailer/caravan?
I have an older type van that isn't very aerodynamic and was wondering if people thought they made a difference or not to drag/fuel use etc.
Pics are Good too:-)

[ltd]

If it goes above the outline of the towing vehicle then yes, use a deflector.

[Crazy Dazz]

Based on my limited understanding of aerodynamics, I don’t believe these work, and may actually make it worse.
The deflector itself will generate drag, possibly serious drag if you get a low pressure zone behind the deflector. Then when it hits the van you get the same impact you would without the deflector.
Unless the deflector was very large and extended all the way back to the leading edge of the van, it is unlikely to be effective. Plus it will be noisy.

[The Yeti]

these were a real popular site in the 70's & 80's on top of falcons & Kingswoods / commodors towing vicounts, franklans and Millards up and down the coast each Christmas

[aquahead2001]

Had a Friend with one and he swore by it.

My experience with the negative effect of aerodynamics when towing came when I went from towing my 15' poptop with a standard EF wagon to a Tickford lowered AU wagon, which was about 50mm lower the EF I think. The EF towed my van pretty well, but the AU struggled. It always felt like it was getting pulled backwards with the van's drag.

The only difference I could attribute to the poorer towing capability was the additional frontal area of the van that was "in the air" due to the lowered wagon. Always wanted to try a deflector, but I never did, I got a Territory instead

[mik]

anything is worth a try in my book, towing one of those big old vans i towed up north with the xr6 pulled the weight easily, but the wind drag at 100 kph it doubled the fuel consumption.

[flappist]

Remember the majority of the drag is from behind the vehicle.

Look at the shape of a wing or a fuselage.

[lamborghinifan]

Well i've done some tinkering this afternoon and whipped up a bit of a deflector. running up and down the same stretch of 100k road in the same direction I tried the deflector up and down. My conclusion is that the terry definitely does not work as hard staying on 110 with the deflector. bit hard to get anything in the way of fuel figures but it's worth the 5 bucks the scraps cost to build it. (I'll pretty it up now I know it works)
Actually last year I towed the same van with my ute which is much lower, and I whipped up a deflector from the top of an A/C unit spur of the moment/night before. Because i'd never towed in that configuration before I had no comparison but the bug splatter seemed to say that the wind missed at least some of the van. The terry's extra height doesn't actually help because I've had to lift the van with oversize rubber to keep the rig level. Pics attached.

[Crazy Dazz]

Originally Posted by lamborghinifan

I've had to lift the van with oversize rubber to keep the rig level.

Couldn't you have lowered the hitch with a different tongue?

Maybe you should write to mythbusters with your hypothesis?

[mik]

that looks ok.

[bigsta]

I had a HZ kingswood wagon years ago with one of those the only difference i noticed when i took it off was that the rear window would get dusty easily and if the tailgate window was down it would suck in exhaust fumes.

I cant remember if it sucked in the exhaust or not with the deflector on though.