My prototype wheel skirt
 

Here's a prototype skirt on my car. What do the experts think? I realise that part of the upper half of the wheel is exposed, thereby lessening the effectiveness of the skirt. But i figured it may allow me to permanently fix it to the car and also not have it bulging out wide enough which may increase frontal area. I know, it's a tiny increase but what the heck!
It's made from foam board and i heated the front and rear bits so as they curve with the bodywork. I also flared out the front a little to direct air around the tire. It took the heat of my gas cooker well, once i experimented with some scraps...:p
It also cut well with a stanley knife. The edges were rounded with a file.
Oh, the duct tape is merely for the picture. I have to make some brackets and a reinforcing rib to go along the straight edge. This may be curved for extra clearance and rigidity.
http://ecomodder.com/forum/member-vt...heel-skirt.jpg

It looks good!

Unfortunately, foam board won't hold up to the elements well over time.

I can't help but wonder if covering more of the wheel wouldn't be a better plan. It would hide more of a moving surface from the airflow. You'd have to sculpt it more, and maybe require more of a pronounced flex on the trailing edge, enough to cause flow separation. That would be Bad, but I'm just spitballing here.

That may be an issue alright. I was planning on painting it so that may cut down some of the uv damage, not that we get much of that round these parts!

Elhigh, yeah it's definitely not ideal but it does help me keep the skirt as flat as possible and also will hopefully allow me to remove the rear wheel without having to remove the skirt.
Hey, if it doesn't deliver the goods i can always make another pair.:thumbup:
Because i'm a sucker for ecomodding!
I'll make the other one later and duct tape them on for testing. I figure i should see if they work before taking lots of precious time making brackets.

ollie

Mercedes has put "partial" rear wheel skirts like yours (minus your "doglegs") on all of its recent crop of efficient concept cars, from the Boxfish "Bionic" car to the Bluezero, to the F700.

All of which suggests if you can't do a full skirt, a partial one is still worth it.

Note that if you do a Google image search on the Mercs, their skirts may not immediately jump out because they often use clear plastic material. This pic shows one in smoked plastic:

http://www.actualidadmotor.com/wp-co...-2-300x201.jpg

PS - you should add this thread to the Project Library. :)

Oops, I was wrong: the Merc F700 has "doglegs" on its clear plastic rear skirts in this pic:

http://images.marken.auto-motor-und-....jpg?r_498x333

Click image to zoom to a much larger view.

reminds me a bit of the greenpeace ecomodded renault twingo
http://i77.photobucket.com/albums/j5...ay/detail4.jpg

so it'll be an improvement over stock i think

Wow! That's probably the closest fit you can get and still be able to remove the wheel. What's the clearance when that quarter of the car is raised? I especially like the flares to direct airflow. Could you post a pic from a different POV, like a view from the rear?

Re: clear wheel skirts - There was a discussion somewhere about clear hubcaps and the problem would be the same - Mud. Clear is good for sterile showrooms, not puddles in potholes.

vtec-e -

I like it. Can you take a picture of the whole side of the car? I think the slant is a positive aesthetic for your Yaris, but I can't tell from the close-up. If you get the snap-in racing disks later, I think it will need to come out more because the cover bows out a bit.

CarloSW2

I'll take some pics tomorrow when it's light outside. The flare at the front is slight and i could have gone more. I don't know how well the foamboard will take to reheating so i might just leave it as is...for now.
Those are some interesting pics of similar skirts. It's kinda funny how i came up with the same shape without any outside influence! My reasoning behind it was the wheel arch tapers in a little towards the rear of the car but the wheel doesn't, obviously! So i slid a straight edge down the wheel arch till it touched the tire at both the front and the rear. This was going to be the lowest point of the wheel skirt and it was sloped as it turns out. If i designed it with an outward bow i would have ended up with a different lower edge. I'll still put a slight bow in it for aero and rigidity purposes and also to give me a little more clearance.
I haven't jacked up the car and removed the wheel yet but i'd say i'll be ok. At the very least i might have to tilt the lower part of the wheel in under the car to clear the studs and remove the wheel. If it's too fiddly then it's back to the drawing board. Should be ok though.

ollie

Who? Me?:o

vtec-e , I think your covers look fantastic ( once painted. )
It just looks ...'right'.
I would suspect that your method is indeed a better way to reduce the frontal area of a wheel skirt, yet have attached flow to the back of the car.
You have a really tight fit all around, and I would think that air will slide right past the wheel without any real turbulence. ( Especially if the wheels are smooth ).

Disclaimer : I have no clue what I am talking about. What I said is pure guessing.

To test this though ( and prove me wrong ;) ) it would really be interesting to see a tuft test around this area of the car ( hey - while you're at it you might as well tuft the whole thing. It's really quite interesting to see how air travels around your car ! )

After looking at the skirts a second time, I think the edges of the skirt should be tapered inward ( like the front fenders of the 1st generation Insight. This would smooth out the airflow behind the tire instead of acting as a parachute.
Do you dare to bring the edges of the skirt ( the sides ) even closer to the wheel ?
Since this is a prototype, you could even just use tape to fill the gap.

Perhaps I shouldn't have jumped to conclusions without a picture from a 3/4 side view. How snug is the skirt around the wheel ?

Cd 0.19
 

The Renault Vesta-II concept used partial covers and still managed Cd 0.19 and 146-mpg.If you must compromise,then "you're there".Looks good!

I left a gap (at the dog-leg bit) of about 8 to 10mm to allow clearance for when the suspension compresses. More at the front as it turns out. I forgot to allow for the flare bit, which opened the gap a little. Since the axle is below the suspension pivot, the wheel will get closer to the rear dog-leg during compression. Not by much i'm sure but i wanted to allow for it anyway. I'll check all that tomorrow and take a few more pics. It'll be hard to take a pic while compressing the suspension though.....
Tuft tests! Yeah that is something i'd love to do. Well, making a video of them that is. I used to have a tripod that would be up to the job, a benbo trekker, but i don't have it anymore. I'll see if my current one will do the job. Otherwise a length of unistrut or something with a ton of duct tape. Yup.....sounds like it'll work!

ollie

Well spotted. I noticed that as i fitted it but just wanted to take a pic for here. As i stand over it i can really see how it protrudes past the tire. Certainly needs some heat to bend it in, which will tighten the gap too. Every little helps eh?!

ollie

You plan to heat it ? I thought it was foam board in this prototype version.


Regarding the tuft testing, do you have anyone that can drive beside you and video ? It would save you the hastle of trying to rig up a camera rig.
It would actually take three people, since you need two people to drive and be looking at the road ahead.
Another option would be to have someone video from the side of the road as you pass by. Using a camera on a tripod would only capture a fraction of a second of the test since the camera would not follow your car, and it would ost likely be blurred.
Also, your camera might get stolen.

( Jut make sure they have a steady hand and know where you want them to point the camera. ) :D

You can tuft test by rigging a camera "boom" on the car aft of the area you're interested in. I did this to look at my rear skirts.

http://ecomodder.com/forum/showthrea...etro-3692.html

Just don't knee-cap any pedestrians.

Hi,

The rear of my skirts do get some outward pressure, even without the "dogleg":
http://img.photobucket.com/albums/v7...d/DSC_2730.jpg
Since this picture was taken, I "rotated" the skirts forward, so that the bottom edge slopes up more towards the back -- and they *still* get pushed outward. To the point where the tape is getting lifted off of the fender...

vtec-e -

Coolio, form follows function.

CarloSW2

I think there has been some confusion regarding the material used. It's plastic right the way through and needs two to three runs of a stanley knife to cut so it's tough enough. Under close scrutiny it is a little porus and this results in it being lighter. The surface finish is ever so slightly rough but has a gloss finish to it. I'm going to take a few more pics now. Won't be doing any ecomodding this weekend as i'll be working. But i'll make a start at it on monday.

ollie

Here's the front flare as requested:
http://ecomodder.com/forum/member-vt...view-flare.jpg
And the full side view:
http://ecomodder.com/forum/member-vt...-side-view.jpg
Rear view:
http://ecomodder.com/forum/member-vt...-rear-view.jpg
This pic highlights the need for an outward bulge. And the very end of it needs work to tidy it up a little.
I'm erring slightly on the side of painting it black as it will stand out less. However, painting it the same as the car would look smart. Any suggetions are welcome!

ollie

TEST YOUR PAINT FIRST! Some cheap spray paints like to eat through foam-plastic.

My vote is for 100% black. It'll make your car look more like the back end is floating.

I like to highlight mods, not hide them, so I vote silver.

Maybe a poll is in order for the thread?

Good point about the eating plastic qualities of the paint. When the time comes i'll test it on a scrap first. Isn't there an undercoat that allows the paint to flex with the plastic? I should probably consider that too.
I've also added a poll to see what the general consensus is. Obviously it won't have a bearing on mpg but it helps if the mod looks good.:)

ollie

It looks good either way.
Do what you want !

Dude!! You photoshop skills are waaay better than mine! I tried it on another pic but it didn't work out. I'm preferring the silver to be honest.

ollie

Thanks !
The bad thing about silver paint is that it shows details such as the corrogation in the material that you are using. Also, if you use spray paint, the paint will tend to have a visible pattern with metallic colors. ( So use a good quality paint and a criss-cross pattern. )
With either color ( but especially silver ) I would suggest maybe adding a small black edge to the bottom lip and curling it under.
You can use black trim pieces that are usually sold for screens at home improvement stores ... or just use some good quality electrical tape if you have a steady hand. If you look at wheel wells on cars, the metal does not end in a sharp edge, but rather has a rounded edge that tucks into the wheel well.

If you go with black, you will find that matte black hides imperfections, as well as makes the piece look professional and not 'cheap' looking.

( Just my suggestion )

vtec-e -

I voted silver, but black still looks cool.

CarloSW2

There aren't really any other black accent pieces on the car, so I say silver.

I like your design as it allows you to check/add air to the tires easily.

I tried full skirts and getting access to the tire stem was one thing I hated about them.

Mine didn't improve fe either, that I could tell.

I voted silver since... that's how I painted mine:) I had a paint mixed to match my car, and even though it's not a 100% match, it still looks good. Cd's pics also suggest making it look like an extension of the car.

I too, like to highlight the mods. Just think, If someone sees your mod, gets curious about it, does some research, and gets hooked on ecomodding like all of us, that just makes the mod worth it in my book.
Also, Krylon make plastic-specific paint called krylon fusion. It's for outdoor patio furnature and such. The only problem is that it won't be color-matched. I painted the plastics on my 4-wheeler with it and it's held up very well, expecially since my fenders are contantly flapping around and bending from bouncing off of trees lol

Yes, it does allow some extra tire to expose the valve for regular pressure checks.
I also am concerned about the potential for non existent FE gains. I'll make up the second skirt with reinforcing ribs for the outward bulge. But i'll just duct tape them on or maybe do up some quick and easy clips for testing. If i get nothing then maybe i'll do some tweaking. If there's still no gains there then i'll not go any further.

Cd; yes, i'll radius the lower edge. Will look much better.

I'm having a few days off work now so i can get busy. My regular commute will restart next weekend so no definite no's till then. I noticed that i have a good few miles on the current engine oil and am not far off an oil change. Combined with the recent drop in temps and i'm going to have to factor that in.

ollie

Looks good, I like your design. Nice hubcaps too, I got the exact same model! I picked the most aero of the bunch they had at the store.

Talk about a global economy: same hubcaps at the store in Quebec and Ireland.

I voted silver - seems I went with the majority for once on these polls :)

Follower...
:P

not covered enough you need to cover the heck out of it LOl.. No drag is what your going for LOL