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Old 09-03-2008, 08:03 PM   #11 (permalink)
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Originally Posted by aerohead View Post
Remember,these are race cars! Their windshields are inside the wake area of the fender-top extractors.In inclement weather,there will be quite a rooster-tail of rain water exploding out the top of those fenders.If it doesn't destroy your vision,it may not be the same for those following in traffic.Also,you may completely destroy the airflow in that area.GTP cars can have drag coefficients like Cd 0.7!!!!!!!!! They're way cool at the track,and they need a lot of brake cooling coming off a straightaway into the first curve.Not the sort of thing we'll be doing on daily commutes.
That's egg-zactly what they were talking about on Top Gear! The new TVR Sagaris has "style" louvers that are actually sealed :

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They were originally open. But, the CEO learned that rocks were flying onto the windshield, so he made them seal them.

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Old 09-04-2008, 03:41 AM   #12 (permalink)
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Fender vents? just finished the vents for a rex,stay tuned,simple matter of venting wheel housing a bit easier than skirting the front fenders.We are talking about genuine fender vents which are totally functional rather than sticky back chromed vents.
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Old 09-04-2008, 08:04 AM   #13 (permalink)
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Most of the models I've seen show hi pressure in the front of the wheelwell and low pressure in the lower rear 1/4. Of course these were stock vehicles no extra bellypan or low hanging air dam.
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Old 09-04-2008, 08:08 AM   #14 (permalink)
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Quote:
Originally Posted by aerohead View Post
Remember,these are race cars! Their windshields are inside the wake area of the fender-top extractors.In inclement weather,there will be quite a rooster-tail of rain water exploding out the top of those fenders.If it doesn't destroy your vision,it may not be the same for those following in traffic.Also,you may completely destroy the airflow in that area.GTP cars can have drag coefficients like Cd 0.7!!!!!!!!! They're way cool at the track,and they need a lot of brake cooling coming off a straightaway into the first curve.Not the sort of thing we'll be doing on daily commutes.
These cars race in the rain though...what do they have, super wipers?
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Old 09-04-2008, 03:19 PM   #15 (permalink)
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If you want to reduce the aerodynamic losses from the front wheel wells, from what I gather you have two ways, which may work best when combined.
1. Minimize air getting into the wheel well in the first place. Flat hubcaps, bumpers that guide air around as much of the front profile of the wheel as is practical, flexible material to smooth the underside of the suspension into the belly pan and wheel skirts covering as much of the open wheel well as possible.
2. Some kind of venting system in an attempt to equalize the pressure (positive or negative) within the wheel well. This could be those above-fender louvers or a vent that lets air out along the side of the car behind the wheel well. Side vents can be as complicated as little chrome grilles connected to the fender liner with ducts or as simple as the Insight's front fender's inward-curving rear edge.

Consider combining a skirt that covers only the front and top of the front wheel for wheel clearance and a vent cut out behind the wheel well through the fender. That should result in less pressure loss or pressure build-up in the wheel well since much of the air flowing towards the tire is redirected along the sides of the vehicle and the rest of the air in the wheel well has an easy way to escape.
Even using just a smooth wheel shape and an inwards-curving rear edge in the wheel well seems to work well for the Insight.

I figure that the best possible airflow would be to use a wheel pant around the wheel itself, like small airplanes and the Aptera, but also to enclose this shape in a flexible skirted wheel well like the Probe V. This way the wheel would get very nearly no airflow (except for what is vented through to the brakes... please don't forget to vent the brakes), the wheel well itself would let nearly no air into the suspension area, and the outer skirt over the wheel well would bend with the wheel when turning without having to scrub against the tire.
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Old 09-04-2008, 04:49 PM   #16 (permalink)
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What Ford discovered with their research for the Probe-IV,was minimize the wheel house volume,then enclose the wheel inside it's own encapsulating steerable fender,which pushes against the deformable urethane outer wheelskirt.Their work is the most comprehensive attack on front wheel drag I've ever read about.It minimized the local drag and also protected all the surrounding flow.If I should ever find time to pursue it,it's the direction I'd go.basjoos articulated front skirts are a masterpiece in design elegance,and probably for the effort,the best value in performance.It's probably the future.
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Old 09-04-2008, 05:06 PM   #17 (permalink)
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super wipers

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Originally Posted by OfficeLinebacker View Post
These cars race in the rain though...what do they have, super wipers?
OfficeLinebacker,you make a good point and my thought is that those cars wipers probably are kinda are super.Even my friend's Porsche 911' wipers floored me! Serious water movement!,and on a production car.With the race cars,The builder may presume that their car will always be "out front" and to -ell with the other racers.Don't know.I have noticed,that in a Beech Bonanza,you don't need wipers,as the airstream is powerful enough to shed the water away.Could be the same in the GTP class,as those beautiful convex $3,000 windshields may help with spray off the other cars.Combined with the fully-articulated single wipers,it may be all they need,and if they don't like it,they can pass into the lead! At least they are all on a closed-course,going in the same direction,the cars are as safe as million-dollar cars can be,and there are paramedics and care-flight helicopters standing by in case of a mishap.And the drivers get paid the big bucks to deal with all of that.Hmmmmmmmmmm where's my Simpson racing suit?
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Old 09-04-2008, 07:01 PM   #18 (permalink)
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Didn't basjoos say that his Civic now sheds rain well enough that he barely needs the wipers?
I was looking into the whole wheel fairing thing. It is disappointing that Ford figured out exactly what I have written above, actually spent money on getting it to work and then shelved the whole idea. I'll bet the engineers who spent years working on the encapsulating steerable fender are even more disappointed.
I think that if you can get to the bolts that hold the shock absorber to the steering knuckle you should be able to use these as mounting points for the rear part of the wheel cover device. For additional strength a few bolts could be put through the brake shield, or you could just replace the brake shield entirely with the back side of the wheel cover.
So build yourself the back plate, and then the curved section that wraps the wheel, and then some sort of attachment system for the front plate. It has to be easy to remove to fill the tires or remove built-up snow. Maybe wing nuts or magnets. It should then be possible to install a basjoos-style skirt.
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Old 09-04-2008, 07:43 PM   #19 (permalink)
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Sounds like Speed Holes
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Old 09-05-2008, 08:56 AM   #20 (permalink)
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Quote:
Originally Posted by lunarhighway View Post
i believe something similar, useing an inverse scoop like setup was first used on a 70's muscle car... can't come up with the name though.

one thing that puzzles me is that this seems to sugest rheres high pressure in the wheelwells, while other sources sugest there's a low pressure...

i could accept eihter case, but i'm running a bellypan i'm somewhat relying on the "low pressure theory" for radiator air extraction.

or is this the reason these sports cars use this setup as well?
I believe NACA Duct is the term you are looking for.

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