Aerofoil towing deflector

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Might a roofbox do the same thing? It would also give extra storage. When I towed I found the roofbox improved economy in places like Germany where towing speeds are lower but in France using higher speeds no difference at all. 

David

We fitted a rack to the roof of our CRV to carry our Oztent, which is basically a 9ft ×2ft open basket.

We drove all the way to Switzerland and back and was expecting it to hammer the fuel economy, but it actually improved it

Very strange.

Gruffy I am just wondered at a saving of 2 mpg will you ever get your money back?

If he drives five hundred miles and then drives five hundred more etc.

On our first caravan over thirty years ago we had a very flat front and used an Escort hatchback to tow it with the aerofoil right at the backand it did appear to help. On moving on to a more streamlined caravan and a Cavalier saloon pushing the aerofoil forward it appeared to make no real difference except to help keep dead flies off the caravan front.

I think with the better aerodynamics of the modern caravan these things do no real good. The downside could be they tend to push the back end down taking weight off the front wheels and that could be dangerous for some outfits on corners on a slippery wet road. 

You need an F1 type front spoiler then to get balanced downforce. 

Regarding getting money back.We do a lot of travelling.I reckon my van does about 7000 miles a year,its 3yrs. Old,the caravan shape as i originally stated is very square,bailey pegasus.this,im sure makes the aerofoil work for me.The test results on this new shape foil are independent,and therefore,hopefully un-biased.

I think you need an estate or similar shaped car with a square rear end and the aerofoil as far back as possible for it to work at all. If it is not near the back of the car because of a boot or long slope then it will be too far away to be effective.