Do wind deflectors work??

On the front of the rack i would say NO because the air can get back in behind it' on the rear probably yes ,look at the Deflectors on most Prime Movers these days, if they did not work they would not have them

Hi Nige, A cover on my boat makes a big differance to fuel economy. With no cover it is like towing a parachute, so I think a deflector would work if set up correctly
Also I have found you get better economy from a stationwagon than a car when towing because it breaks the wind better

Cheers Pete

I had the large aluminium deflector on the front of my roof rack (see my rig pic on this reply), but have since removed it. I don't believe it improved fuel economy nor did it reduce the roar of the air passing over/through the roof rack. I don't tow a full size caravan, just the camper trailer.

I can't see that they would do much really. On the trucks the main benefit is smoothing airflow, cutting down gaps is really important and reducing turbulence. I would imagine that the air deflectors at the front of a roof rack would have a good chance of increasing turbulence and worsening economy. I can't imagine that it would smooth airflow over the top of the van when it is so far back.

Having said that, I would imagine that the rounded cover like we have on our ARB rack would help a small amount to cut down turbulence around the rack - does make it quieter.

Have a look at this link - I can't make it a direct link as it is a PDF I imagine.

http://www.kenworth.com.au/kenworth/pdf/Cummins_Fuel_Economy_Guide.pdf

On Page 10 there is a discussion about aerodynamic skirts on trucks and some simple diagrams that make me think the thing on the roof rack is a joke.

Andrew

Andrew

Yes you would be better to have nothing on the roof (no rack at all) and fit a ropunded frount section to the caravan or camper.

Once you get over about 80 km the drag caused by the flat rear of a caravan probably exceeds the direct frontal resistance.

A low profile van or camper greatly reduces the drag compared to a square box caravan.

I have built a low profile, aluminium camper with a streamlined front box and I now get better economy than when I had a roof rack with all my camping gear on top (and no trailer) dispite being about 400kg heavier with the camper trailer than with the gear on the roof.

If you have a small wind deflector on the roofrack to deflect air over the gear on the rack, yes it should help a little with streamlining the rack but not with the caravan.

Nige,
There's nothing quite as believable that a bit of here say so I thought I'd share some with you.

I had a long chat to a bloke in a Mt Isa Caravan park recently about the wind deflector he had fitted to his Patrol. He towed a full height Coromal tandem and he assured me that the wind deflector, which he fabricated, made a noticeable difference to his fuel consumption and he had very few if any squashed bugs on his caravan after fitting. The deflector was positioned probably about over the rear wheels or a little further back. He said that he experimented with the angle of the deflector as well as the positioning until he found the optimal position and angle. His one complaint was that his deflector was straight ( across the vehicle) as opposed to being curved so his next experiment was to curve the deflector especially at the ends and also to make it a bit wider.

Tom

For something a little different you might want to have a look at these.

www.airtab.com/

Nige,

They are great for advertising.

As far as wind noise goes with a roof rack, I think it has a lot to do with how far back the roof rack is positioned on the vehicle.

It would help with air flow, as I my case where I sometimes carry tarps on the roof rack. I put them directly behind the wind deflector and this helps with them not flapping around.

For tow a full size van I would think that the closer to the van the better. Positioning the deflector to wards the rear of the vehicle would be better and the only way to know how far back would be to experiment.

A wind tunnel test would be best but we all don't have one of them in the back yard.

For data I would try Caravaning Forums or even the likes of the NRMA and see if they have done any studies on the subject.

Wayne

hullo nige
i run 2 deflectors 1 at the front of the pack rack to push the air over all the b/s on the rack and a second deflector at the rear on the patrol just about the rear wheels ,fuel consumption probably doesnt do a lot but when trucks are passing and overtaking yes i know the difference the only trucks that have a real effect are the animal movers that seem to drag the air with them
but in my case and cicumstances i believe it helps and yes i tow a full size van
also the rear deflector is veed

steve