Roof rack and wind deflectors

Ray,
I have not taken fuel readings after adding, but it seemed to help.
Other advantages are lower wind noise and no splattered bugs on the gear stored on rack so helps to keep the better half happy.
I made mine out of a sheet of PERSPEX from BBC (Bunnings) for $15. Cut with fine tooth hand saw and bend with heat from wifes (or your) hair dryer. Hold in place with stainless screws. Whole lot $20.

Hope this helps
Vince

Mal

Where do you get sheets of polycarbonate from in brissy ?

Ray I've used a deflector made out of thin aluminium sheet for years on a 3/4 rack on a 75 series troopy.
The roofrack lops around 2mpg off the fuel consumption travelling at 95 -100 kph.
Fitting the deflector did little to the consumption but made a huge difference to noise and buffetting. Also as someone else said it keeps the fauna off the rack bag, also deflects tree branches up and over if it is close enough to the roof.
The roof rack was composed of three heavy duty loadrails (gal ones) with a gal pool fence panel as the base covered with marine type carpet. Load consisted of a spare 7.50 x 16 tyre case, a 4 foot square rackbag and a small bag with a rolled up fuel bladder. The rackbag only had sleeping gear and light stuff in it nothing heavy.
The wind deflector was mounted off the front edge of the fence panel with aluminium flat bar brackets from approx 1" off the roof to the height of the tyre case at an angle of about 45 degrees.

I made mine from a sheet of acrylic (perspex). bent by careful use of the barbecue (enclosed type). Cost less than $20. TJM roof rack on 1990 Rangie.

Effect???? HUGE REDUCTION IN WIND NOISE!!! HUGE HUGE HUGE!!!!

Fuel consumption not measured, but I work on the theory that all that noise requires some energy. Less noise = less energy required, unless it is being turned into some other form of energy ie heat which I doubt.

Anyway if it cost me more fuel, I'd be happy 'cause I could't stand the noise

G'day Ray,

I've got a mate who specializes in aerodynamics (aircraft designs) and a while back we got talking about wind deflectors on roofracks and whether or not they do improve fuel economy. He told me that the only way to improve the aerodynamics of practically all 4wd vehicles would be to completely remove the front end bodywork and replace it with the nose off the XPT train. In other words, just about all 4wd vehicles have the aerodynamic design of a backyard shed and the fitting of a wind deflector to the roofrack would have such a minimal beneficial effect on fuel economy that it would not be noticeable.

Another thing to consider is the angle of the deflector and the only way to determine if you've got it right is a wind tunnel test or you could fork out around 25 thousand dollars for state of the art computer software that simulates wind tunnel testing.

The bottom line? They're good for keeping bug guts off your load and thats about all.

Diesel1

Hi all,

Thanks for the replies. I see what you all mean by the wind noise, if I can't reduce it with the deflector the roof rack is coming off.