Tire Fairings
 

What kind of fairings should I put in front and behind the tires to reduce wind drag?

Hi Tony,

Darin had them (briefly) on his boattail, and I have 'em on my Scion xA; I think they are called strakes:

http://ecomodder.com/forum/showthrea...tml#post143382

http://ecomodder.com/forum/showthrea...tml#post209920

OEMs put simple, flat pieces of plastic in front of the tyres.
They put them pretty close to the tyres, and a bit more to the middle of the car.
They sometimes curve the inside part around the edge of the wheel well (i.e. facing more towards the middle of the car)

As for strakes after the tyres, a wedge shaped structure with shallow angles will do.
Put it as close to the tyres as possible, and make it no wider than the tyre itself.

It would probably be even better if you used the shape of the streamlining template, but that's rather complex in 3 dimensions.

i'd try to coppy what you see on oem car... these things are a result of windtunnel and on road testing and are a compromise between good aero and ground clearance, and impact resistance. they're not prefect but if your car doesn't have them they're gonna give you a little improvement. get down and measure some cars that have them as eyeballing the scale can sometimes be deceptive. going to low can hurt aero but also you quicky lean that even with carefull parking and driving, ramps and bu

you can also go for compound dams where you extend the airdam slightly in front the the tires and place even larger dams directly in front of the tires

you can use coroplast and as long as it doesn't folds along the ribs it's quite strong, alternatively i've used cheap flexible cutting mats from ikea they're just sturdy enough and because i screwed them to the curved plastic inner wheel well liner the cure adds extra rigidity

Tony, I really like your coroplast covers. I am going to copy them. My mini van has a lot of cutaway around the front of the wheel wells. I did some quick and dirty molds from heavy wire and dacron fabric (similar to the gritters liner) and covered them with carbon.

Here is what they look like. I also had used a similar technique with my grill cover.

I made a rear fairing from the wasted skirt. Should have put it closer to the tire, looks like kind of a scoop. Needs a little black spray paint.

http://farm6.static.flickr.com/5102/...8902231412.jpg

http://farm6.static.flickr.com/5262/...e44fd85141.jpg


Hi Dave,

How does the carbon fiber hold up? How many miles does it take to break even? How did you jump from 40 mpg to 57 mpg on the diesel Joetta?

You really have a way with coroplast Tony. Your bicycle always was one of the best super street bikes out there. Do you still have the chain drive steering.

I don't know exactly why I am getting better VW FE except that I did make a coroplast bubble on the hood and moved my coroplast grill block out to the front of the bumper. Had a lot of folks say that it doesn't help much if at all. Guess I should take it back off and if I am lucky my mileage would drop. Actually I have been getting avg of 49 for the last 1400 miles. I would be screaming up and down if I were getting 57.

I am not an engineer and don't do enough trials. I did add 2" to the stock spoiler and the mileage went down 2 mpg from my last fill. I know the wind was higher as spring is comming on. I am tempted to remove it. Perhaps it is adding frontal area and drag. I can't come to grips with having a lower body panel. I'm 60 now and don't like crawling underneath. I'd like to just cut loose and get a Tourag v10, let it shift itself and go like a billygoat in the snow.

I have a lot of carbon fiber in my shop and didn't have to purchase it specifically for the mini van project. I had it on all winter and didn't have any issues with it. I used probably 18-20oz of cloth. I got the idea from a tv show where they were stretching cloth to make speaker enclosures for punk cars. I thought that it might be a good way of making an aerodynamic shape. I used some 9 ga wire from some old election signs and reinforced them a bit, sewed on some cloth by hand shrunk it with a heat gun and spray glued on the carbon (any composite would do). Painted on the epoxy and once cured peeled it apart. If you make some wire frames up that fit your car well I can make them in carbon for you. I used some pop rivets to hold them on.

I really haven't figured out a way to get the smooth contour for a tail box. I think I want to use this technique. I was thinking that I might make it in sections and then turn them over so that the slope goes the right way.

[dreammode] Maybe having the concave areas at the front of the tail box might make shape like some of those laminar flow shapes like the weaver liner. [/dreammode]

The newer Jetta has a cd of .3 and my older one .36 Assuming a similar frontal area they have 20% less aero drag and a more efficient engine to boot. No wonder they break 50 pretty easily.

Tony, is the face of it next to the back of the tire covered?

No, Niel, right now it's an open scoop. I have some LDPE packing foam filler to hot glue in it.

I wouldn't worry to much about the scoop effect, if the air cant get out at the back it'll just be filled with static air travling along with teh car, also it's open face is shielded by the tire so it's not directly exposed to the airflow, and this is improtant because any difference in drag between an open and closed face largely come from the fact that with a closed face there's a stagnation bubble that acts as a crude nose cone, making the air pass cleaner over the edges... as the tire has already pushed the air asside, an open or closed boattail won't matter much... however there's not benefit either to having them open so, if you can close them go ahead

Not air, but water, mud and debris filling the scoop.

Dave, I have chain steering on my commuter bike. I went to push rod steering on some newer bikes. Chain has unlimited steering, its hard to get more than +/- 35 degrees without the rod hitting something, but its better for narrow Q. I am in the process of designing-building a new bike I want to try a over the shoulder space frame.

http://www.crazyguyonabike.com/doc/?...27&v=2i#182576

A bigger concern is the scooping of gravel, and in the winter around here, you would fill it with slush and snow and ice; which weighs a lot and could tear it off the car. I like the "seamless" construction of these.

I put the right rear fairing on last night. Now I have to figure out what to put in the front. Thanks Niel, for the tuff post.

I filled up, $46, wow $4.299 for regular 81 octane with 10% ethanol, and that was the cheap station. Got 43.5 mpg with the over size tires, 95.2 mph max speed... oops.. forgot the speedometer is slow.

Though I got better mpg, it seems like the car has more wind drag and doesn't coast as well. Hopefully the tire fairings will help.

I am thinking about octane booster, since I can tell the timing is being retarded when the engine is hot under load.