Air dams?

[aerohead]

Originally Posted by woodstock74

I don't know man, I really don't think they're doing all that much tunnel testing/CFD. At least not for the lower tier "econo boxes". If they were we'd struggle to find gains. In my career we'd spend hours in the wind tunnel and be happy to walk out with 1% reduction in drag. But this was on a highly refined race car. People on these forums are finding chunks without resorting to drastic changes (and they're finding huge chunks when they do). This speaks to a fundamental lack of development and refinement. We have to face it, cars are designed these days by accountants and focus groups. Yes, there are the exceptions: where it's profitable and can be used as a selling point.

A point made by styling chiefs decades ago,was that if $billions were required to push up mpg with a new engine,a few $million could do the same with streamlining.
Since CAFE is measured on a sales-weighted basis for the automakers 'fleet',if these econoboxes ARE optimized for mpg,without affecting styling,then the better mpg here,allows more sales of highly profitable lower mpg designs.
So actually,the bean-counters drive the streamlining based on profit motive,share value to the stockholder,corporate image,marketing advantage,and compliance with EPA regulations.
Sure it's been a slow incremental process but when you consider that the cheapest car sold today could embarrass a Corvette of my college days,there has been advances.
Hucho put an airdam kinda like yours on a VW 1600 and it raised the Cd by 0.04.
There is no a priori knowledge about how any production car might react to any particular modification.We mod at our own peril.
Given market competition I would be very reluctant to presume that any of today's automakers are attaching anything to their cars arbitrarily.It would be antithetical to capitalism.

[woodstock74]

Once I hit upon the best depth I'm going to convert the carbon extension to something more curb friendly. What plastic would be best for that? ABS? Or some kind of stiff rubber?

[aerohead]

Originally Posted by woodstock74

Once I hit upon the best depth I'm going to convert the carbon extension to something more curb friendly. What plastic would be best for that? ABS? Or some kind of stiff rubber?

ABS is great material but will shred or bust in a nasty ground strike.Corvettes,Trans Ams,and New Beetles can't seem to hold onto their's.
I stumbled onto some urethane foam shop floor pad material at BIG-LOTs back in the tool and hardware section.You get about 16 Ft SQ for $15 (US).It's gray in color and has a star-plate kinda pattern on one side.I flipped it and used the smooth side.It bends onto curbs nearly every day for 2-years now and has held up well to the U.V.Since it's a neutral density gray 'color' it goes with any body color.
I've recycled chin spoiler material off Volvos out of boneyards.It had a perfect stiffness vs flexibility.But I really like this foam floor pad.
The plastic lawn edging will do also.I've used it all.
PS,Big Dave has used rubber conveyor belt material to good effect if you can find a local source for that.And it's black.

[kach22i]

Originally Posted by aerohead

....urethane foam shop floor pad material

I'll have to try this material when extending my own front spoiler.

[JRMichler]

McMaster-Carr, McMaster-Carr, has many different types of conveyor belting. One type is listed as "impact and abrasion" resistant. That belt should make an air dam that will tolerate hitting the road.

[woodstock74]

Originally Posted by JRMichler

McMaster-Carr, McMaster-Carr, has many different types of conveyor belting. One type is listed as "impact and abrasion" resistant. That belt should make an air dam that will tolerate hitting the road.

That impact and abrasion resistant stuff is $8+/foot. I'm looking at the General Purpose PVC 4" width, $1.62/foot. As this is a "belt" I take it it has a lot of flexibility? When I think of PVC I tend to think of rigid (shatter prone in impact) PVC pipes.

[woodstock74]

Thought I was going to be clever tonight and lower the airdam another 2"...well, it doesn't clear the driveway. And another 1" doesn't either. So back to baseline. Only have about 1/4" clearance there (it's pretty steep). So I think it imperative to get something with a little impact resistance and I'll be looking at those belts. Need to think of what MkII airdam will be though (always looking to improve...).

[Sporty Modder]

I really like the design you have right now. The only thing I personally would do is widen it, go about half way across the tires on each side and call it good.
I dont think going any lower will help.

[woodstock74]

Originally Posted by Sporty Modder

I really like the design you have right now. The only thing I personally would do is widen it, go about half way across the tires on each side and call it good.
I dont think going any lower will help.

Problem is finding attachment points beyond the current width. Currently I've attached the airdam to the floor insert I made. I'm thinking MkII might entail attaching brackets to the perimeter of the bumper return. This would move the airdam forward of the current location and would allow me to widen it. I'll have a think.

[Sporty Modder]

Can you show /describe how it is attached now?