Brainstorm: rear wheel fairing

[Fortuna Wolf]

I will have some time in the next month to sit on the driveway with and see if I can come up with something.
I am going to sit with a large block of foam and carve a model of a fairing for the rear wheels, then make a negative master with fiberglass (got any better suggestions), and then use that to make a the fairing in fiberglass.

I can't promise any mpg gains, but would anyone be interested in these (even if just for looks) as a kit so that I can pay for materials and make it worth my time to do it?

 

[mdt]

...anyone be interested in these (even if just for looks) as a kit so that I can pay for materials and make it worth my time to do it?

I've been scheming about making a set of fairings like this for quite awhile. I'm definitely interested in helping out. It'd be ideal to get input from someone who has some real world aerodynamic skills. The tricky bits to me are:

1. How low can you go and how close can you get and still have safe clearance for the full range of motion of the wheels? (need to articulate the wheel with shocks/struts removed while taking lots of measurements)
2. Will fairings dangerously effect the ventilation of the rear disk brakes? (prolly not...)
3. How do you make them relatively secure, but easy to remove/attach? It'd be best to not have to drill into ext. body panels when attaching the mounting hardware.

Thanks for getting the ball rolling for this FW! It's a long overdue mod!

-mt

 

[Fortuna Wolf]

1. I was going to make them flush with the bumper and side of the car. That way it doesn't look stupid and if something bumps the wheels higher than that you're already bottoming out.
2. Doubt it. I suppose we could do some real world testing with a high temp thermocouple and a track. If someone sends me a thermocouple and thermometer I will gladly tape it onto my calipers and get the data.
3. I was thinking about drilling and installing support brackets inside the wheel well, and then you would put the fairing onto them and attach it with some small bolts. If you wanted a design that clips it it won't be 1) as secure, and 2) will cost a lot more to fabricate. Its easy enough to make a fiberglass sheet and drill holes through it, but to fabricate it with clips economically would require something like injection molding in large quantities.
4. I've never done a thing like this before. Eek.

 

[mdt]

1. I was going to make them flush with the bumper and side of the car. That way it doesn't look stupid and if something bumps the wheels higher than that you're already bottoming out.

I don't have my car in front of me, but I'm assuming when you say flush to the bumper and the side of the car, that you simply mean flush to the side of the car. As a first pass it's prolly easiest to do this, but to get the fairing lower than rear axle will require having it not be flush with the side of the car, right? I mean at some point, the rear wheel protrudes out from the side of the car. So were you considering mebbe just covering 50ish percent of the wheel like the following fairing?

http://www.recumbents.com/car_aerodynamics/#Fair%20the%20wheel%20wells

I'd like to get a bit more coverage on the wheel, but I realize that getting any more coverage requires a curvaceous and therefore more complex fairing.

Eek!

 

[Fortuna Wolf]

Well, I meant, flush horizontally. I would then flare it out so it could pass over the wheel at the bottom.

 

[basjoos]

Here's a pic of the rear wheel skirt I installed on my Civic CX. The upper portion is permanently attached to the sheet metal and the lower rectangular portion is attached using velcro along the top and a bolt screwed into the frame at each lower corner so it can be removed for tire maintenance. The material is Coroplast with a curved aluminum bar attached to the bottom to flare the cover over the portion of the tire that protrudes out from the frame. Its been on my car since May with no problems. That row of screws on the left of the photo is not part of the rear wheel skirt, but is rather part of the boattail attached to the rear of my car.

Rear wheel skirt

 

[Fortuna Wolf]

Uh, well, did it increase the mpg at all?

 

[Brock_from_WI]

I am interested as well. Seems like a great idea, I would be curious to see how it might effect our cars mpg.

 

[RabbitGTI]

Here's a pic of the rear wheel skirt I installed on my Civic CX. The upper portion is permanently attached to the sheet metal and the lower rectangular portion is attached using velcro along the top and a bolt screwed into the frame at each lower corner so it can be removed for tire maintenance. The material is Coroplast with a curved aluminum bar attached to the bottom to flare the cover over the portion of the tire that protrudes out from the frame. Its been on my car since May with no problems. That row of screws on the left of the photo is not part of the rear wheel skirt, but is rather part of the boattail attached to the rear of my car.

Rear wheel skirt

Post photos of the whole car.........please.

 

[Fortuna Wolf]

You know how there is that flat lip around the wheel well? I may try making a something that fits over that lip with a clip (though, screws would be far better)

 

[basjoos]

The rear wheel skirts increased my mileage by about 3mpg.

Here's a photo of my whole car.

 

[Fortuna Wolf]

inquiring minds want to know, what was the before and after mpg?

 

[TurbinePower]

Changing a tire on that thing must be a real PITA...

 

[RabbitGTI]

Are the clear attachments on the front and back plexiglass?

 

[moondawg]

That is the coolest thing I have seen in a long, long, time.

Kudos for wanting to increase your economy so much!

moondawg

 

[basjoos]

The initial mileage was 51mpg (summer), 44mpg (winter). I am currently running about 70mpg.

To change a tire, (front wheel), release the 2 retraction springs on the bottom of the skirt, flip the skirt up out of the way, remove the hub cap, and then you are removing lug nuts. (back wheel) Unscrew 2 phillips bolts and loosten the velcro along the top of the skirt, set the skirt aside, remove the hub cap and the lug nuts.

The clear glazing is clear vinyl, which is a flexible, but sturdy material also used for windshields on boats and ultralights.

 

[njkayaker]

The rear wheel skirts increased my mileage by about 3mpg.

Here's a photo of my whole car.

What's the mpg of the unmodified car? 3 mpg seems awfully high for improvement provided by the wheel fairings. Cool looking car though.

 

[Fortuna Wolf]

he said 51 to 70. Which is quite impressive really.

 

[mdt]

Basjoos - Do you still have use of the hatch with the cowling on the back?

Very cool use of easy-to-find hardware!

-mt

 

[njkayaker]

he said 51 to 70. Which is quite impressive really.

"The initial mileage was 51mpg (summer), 44mpg (winter). I am currently running about 70mpg."

It's not really clear what he is saying.

 

[basjoos]

Since my car has a 2 piece hatch (like a mini-station wagon), I don't have the use of the hatch. If I had a 1-piece hatch like a typical hatchback, I would simply have mounted the boattail to the back of the hatch so it would lift up with the hatch as I opened it (sort of like the front door of the C5 military transport jet).

With the car is its stock condition, I was getting 44 mpg in the winter and 51mpg in the summer. I am currently getting about 70mpg, whereas the car in its stock condition would normally be getting 46mpg at this time of year.

 

[mmmchickenboy]

at what speed do you realize this fuel economy (70mpg)? i would guess 55mph, but with the amount of modification you have done, i'm wondering if the target speed has shifted.

 

[catmandoo]

what you talk of is nothing more then a fender skirt,lots of old american cars of the 60's-80's had them.go find one and check em out they usually have a lever right underneath the middle.the ones on my 66 pontiac you push up then in on the lever to release from it's locking tang,then pull down.this releases the 2 outer tabs that hold it in place,i think if you reinforced your skirt you could also use this kind of arrangment to hold yours on.if it's fiberglass it's not gonna weigh too much,whereas my old pontiac they probably weigh 10 lbs apiece at least.

 

[basjoos]

I'm getting the 70mpg in my usual day to day driving and commuting (52 miles each way). Most of my miles is interstate driving at 55 to 70mph, combined with some rural backroads at 45mph and urban driving at 35 to 45mph. On my most recent (in late Sept) long distance road trip on the interstate I got 66mpg at 75mph, but I have added some more aero mods since that trip and hopefully should do better than that now.

 

[bikeprof]

basjoos. THAT IS A WONDERFULL VEHICLE!
It is so "Star Wars...", GREAT!

I am hoping to do some MODS. on my wagon but not so drastic.
I remember your tire spoilers, that is one of my first aero mods. with the rear wheel fairings and wheel covers.

YOU are such an inspiration...