air dam material
 

I have heard people saying that they used sheet metal to make their air dams, but has anyone tried aluminum flashing? Just wondering how well it works compared to sheet metal.

If you hit an incline or something and bottom out, the steel will bend back into place. Aluminum does not, it will break.

Black coroplast. It bends right back even after a good whack. Some people use lawn edging, it's forgiving to a smack, too.

I used coroplast for the airdam on the TDI. I installed it in march and it's holding better than I thought it would. It almost looks as good as new. I scraped it down a couple times, but it flexes nicely and comes right back in place. I can not think of an other material that could have done a better job honestly. Also, if you have a longitudinal bend in your dam, the coroplast will resist real good to transverse forces, it won't bend under the car at speed.

Where could I get black coroplast or should I just use lawn edging? And it doesn't bend at high speeds? What did you attach it with, just sheet metal screws? How well does it hold paint?

I bought a roll of lawn edging but, imho, it was too floppy and easily bent to stand up to an oncoming 60 mph wind. I could picture it folding back flat.

Coroplast is pretty stiff and can hang in there against the wind, not to mention against the occasional curb or steep driveway entrance (I should know!).

I installed mine by first folding it over the edge of some 1" X 1" aluminum angle. I'll have to post some drawings of how I did that, it seems to be working out well. The 'plast is pop-riveted to one of the angle legs, wrapped around the angle to the other leg, and then #10 X 1" sheet metal screwed to the underside of the car.

From the front to back, we have coroplast (with pop rivet "good sides") facing out, then one leg of the aluminum angle (with the pop rivet "ugly sides") facing the back.

From bottom to top we have the other angle leg (with the screw heads), the layer of folded-over 'plast, then the underside of the car (penetrated by the screws). Held this way, the 'plast is backed up by the angle pretty well against oncoming wind and obstacles.

Edit to add: I got my coroplast at a local sign shop. It was a special order 6' by 2' black piece, cost me $12. It's easy to trim with a knife or scissors but gluing it may be a challenge.

Have a look at my TDI in the garage entry, you'll see the airdam. I just screwed it in the lip under my bumper with 7 screws. I actually got white coroplast covered with black vinyl which was leftover from a sign shop job.

Has anyone tried Kydex (thermoplastic) for an air dam?

I haven't yet but I'm trying to get my hands on some, I love the stuff, easy to form with heat, EXTREMELY rugged and looks pretty good to boot. If you know of a good place to get it for a reasonable price i'd be interested to hear as I am not sure if my source will come through or not.

I did mine out of aluminum siding because it was free. True, if you kink it to a sharp bend, itll break sooner than steel. But I had no problems with it breaking as I was forming it. I even folded the ends back and relocated the bends a couple times on the drivers side. Also if you bottom it out, itll most likely fold over gradually and you can pull it back. You wont actually land the entire front end of the car flat on the road. Also a plus is that it is more malleable than steel, so at the absolute worst if I lose it somehow, itll deform rather than poke a hole through my steel gas tank or oil pan or other things. I dont see that ever happening though, it is on there better than the airdam on my 6000 wagon and that one is still there. Really it is quite rigid though with a longtudinal bend at top and bottom.

garys_1k -

I was thinking the same, especially the lawn edging.

Also, I was thinking that you could back it with spongy foam to act as a spring. It would be light-weight and would allow the coroplast to compress/bend up and bounce back after hitting a speed bump and other urban predators of low-profile air dams. If the foam is integral to the air dam support structure, it would need to be "rigid" enough to withstand highway "wind" speeds (i.e. 60 MPH).

CarloSW2

I had seen some black lawn edging at Home Depot that had a thicker wall than most. It was a professional grade. It would have stood up great for this use, but when I went back to get it they didn't have it. All they had was the thin stuff that I would stay away from for this project.

Material for air dam
 

I replaced the lower front bumper lip of my '93 Prelude with 6" of 1/4" thick neoprene rubber. It is held in place with two full width sections of 1" aluminum angle stock cut and bent to perfectly match the shape of the factory lip. The rubber is held onto the angle stock via 1/4" stainless steel hex-head bolts. Ground clearance is 1". This was just added to my car so I will report the impact on gas mileage after my next tank.

Ive had mine on for almost 2 weeks now. Ive scraped it several times in gravel and it didnt do anything to it except make it dirty. Today I scraped on this one steep transition in pavement that my travel trailer bottoms out on all time. It bent it a little, didnt kink it at all. When I got home I straightened it with my fingers and besides a little chipped paint it still looks just fine. Not bad for free. I should hit it less and less as Iearn which places Ive gotta watch out for.

I belive that is the stuff that I got. They had it in 10' rolls. I cut it to fit and fixed it to the car with about 45 zipties thru holes I put in the underside of the bumper and the lawn edging. I then got one of those aluminum threaded rods and put it in the hollow loop on the bottom end of the edging, and used it to let me bend the lip to match the U shape for the bumper. Works well. I didnt have a drop in mpg, but also no gain (numbers are right where they always were) but I also do mostly low speed city driving (stop/go, about 45mph average).

i will post some pictures later.

http://i30.photobucket.com/albums/c3...t/DSC00103.jpg

http://i30.photobucket.com/albums/c3...t/DSC00105.jpg

the fatter pat at the bottom is actualy hollow, so I put one of those threaded aluminum rods in it and bent it to the shape I wanted, has held up well for the last few months/1000 miles.

I want to fiberglass over the center grill in the upper parts of the picture in the middle of the headlights), as it doesnt let that much air in and may help with overall airflow over the car.

Looks good. My Accord actually has a place for this to mount and with holes for the anchor nuts too. Aerodynamically speaking you would need to be traveling faster than 45 mph to see any noticeable gains. How clean is the underside of your car? Possibly a belly pan or filler panels may help some, but again at higher speeds. Most of my driving is highway, I would say 90%.

geoff -

It looks great, but I am not sure what you mean by "aluminum threaded rod". Do you mean for garage shelving or ?!?!?!?

CarloSW2

Exactly, it comes in different lengths, easy to cut with a hacksaw and also easy to bend while being lightweight. I chose it over just a regular rod because I figured the threading on it would help it "bite" into the platic lip and keep from sliping out of place. Along with the fact that it bends in on the edges and I sealed the ends off with silicone its been good, its just there to help it hold its shape in the wind.

Yeah, I do mostly city driving, I wasnt looking to get a huge gain out of it, and for the total cost invested (about $25-30) along with an hours work I was happy just to not loose any MPG. I havent seen any measurable gain or loss with it over the last 3 tanks of gas since I put it on (about 1000 miles and 2.5 months). I do almost completly city driving, only occasionaly going over 50mph. Ive heard that aerodynamics really only come into play with more modern cars above 55-60mph.

My office will be moving at the end of the year, and my 6 mile each way commute will be turning into 25 miles each way, with about 20 miles each way being highway, so I hope that things dont change that much adding an extra 10-20mph to my cruise speed (about 65mph from my now 45-50mph)

As for an undertray, the car has 3 different peices that run from under the radiator back to the mid point of the engine bay. I plan to get some of that corrugated plastic to help tie those 3 peices together, and carry the undertray further back, closer to the firewall.

Looks great Geoff. I had to read the message to see what you did, it looks like a factory part of the car.

Thanks, I am going to be painting the car black with the help of a friend that owns a body shop, I am interested to learn how to paint a car, ive already been trying some basic body work, filling dents on the car and holes left from removing the factory wing and badges on the back of the car, as well as the side door bump-gaurds and sanding down some paint bubles and minor surface rust. When the car is black it should really make this front lip blend in. The car has about has about 5 inches of clearance, the front lip reduces that to about 3 inches. The new springs I am looking at getting would lower the car by just over 1 inch. The lip is made out of pretty tough plastic, and the way its mounted it can spring back it it hits a curb or scrapes on a driveway.

The only thing I am not sure of is (as others have mentioned) how much the lip deflects in the wind at speed. Maybe i will have a chance to drive next to a friend on the highway and have them take a picture at various speeds (50, 60, 70 and 80) to see the effects. It I find it deflects to much to be useful I may try to fiberglass over it, and actualy moulding it into the bumper.

That's really not the case. Aerodynamic drag starts to become significant at the point where it requires more power to overcome the aero drag than it does to overcome the mechanical drag. There's not a lot of mechanical drag in your car, so I'd say the aero starts to land on the heavy side of the equation at just 20mph - less for some cars, more for others.