New air dam

[JRMichler]

The factory chin spoiler on my truck had broken into several pieces years ago, and the duct tape holding it together had been replaced several times, so I decided it was time to make a proper air dam.



I wanted something slightly lower than the factory chin spoiler, plus it had to be sturdy enough to smash into a snowbank or plow pile without damage. So I bought some conveyor belting, stainless carriage bolts, silicon bronze nuts and washers, and built an air dam. The bottom row of bolts fasten to angles that bolt to a second piece of conveyor belt intended to add stiffness to the visible piece. I have not yet observed whether the air dam flexes back under wind loads on the highway.

Unfortunately, I cannot properly test it. Any MPG difference from the factory setup will be small, and my driving habits will change since I retired last week.

[Erasmo]

Looks good. Any plans to eliminate that antenna?

[freebeard]

I support the decision to upgrade, but for the stock pieces after duct tape the next step is:



Else Zip ties.

[aardvarcus]

Looks good! I like that it is out at the leading edge of the vehicle. Even if you don't notice the MPG as much, I bet you will notice the better handling that would provide to direct more air over and around than the factory setup.

[kach22i]

Originally Posted by JRMichler

The bottom row of bolts fasten to angles that bolt to a second piece of conveyor belt intended to add stiffness to the visible piece. I have not yet observed whether the air dam flexes back under wind loads on the highway.

Please post a photo of your setup for lower lip bracing, it sounds interesting.

Below is my solution, obscured in the photo is the cross bar forming the big "U" shape for the metal. The lower lip is braced only for about 18" in the middle, but works because of the curved shape.

Chin Spolier - fast/easy/cheap/effective - Page 2 - Pelican Parts Technical BBS

I did a 80 mph test, the front spoiler concaved on me at the middle, needed additional support. ...........

I attached aluminum channels to the ABS rock guard, and notched the channels with a grinder, and then bent into an arch and attached with bailing wire a steel wall standard (shelving type) to form the bow reinforcement.

You are looking at two layers of chin spoiler plus a splitter, it's quite the mess under there but works and looks good from the outside.

[MobilOne]

Congrats on the retirement! And the chin spoiler.

[JRMichler]

A photo showing the air dam stiffener from underneath. The angles are UHMW plastic from McMaster-Carr ($3.00 per foot).



It does a good job of holding the air dam to the same curvature as the bumper out at the ends, but I suspect the middle blows back. I'll be adding a couple of braces similar to what Kach22 did, except my stiffeners will by something 1/8 X 1 steel so that I can bend them back easily after contacting a snow band.

[JRMichler]

Snow collected inside the grille block when driving through falling snow. My guess is that a lot of air is coming up from underneath the new air dam. If so, there's more air going through the radiator than needed. If so, that excess air is AIR DRAG.



Thoughts or suggestions, anybody?

[ECO-AKJ]

Originally Posted by JRMichler

A photo showing the air dam stiffener from underneath. The angles are UHMW plastic from McMaster-Carr ($3.00 per foot).



It does a good job of holding the air dam to the same curvature as the bumper out at the ends, but I suspect the middle blows back. I'll be adding a couple of braces similar to what Kach22 did, except my stiffeners will by something 1/8 X 1 steel so that I can bend them back easily after contacting a snow band.

Looking at this picture reminds me of those wind tunnel tests of a box trailer and the air just swirls at the back, it may be doing so here in a similar fashion.

[kach22i]

Originally Posted by JRMichler

My guess is that a lot of air is coming up from underneath the new air dam.

Originally Posted by kingster1989

Looking at this picture reminds me of those wind tunnel tests of a box trailer and the air just swirls at the back, it may be doing so here in a similar fashion.

I'm wondering if a small splitter would be enough to establish a "plane".

This plate splitter or plane would not only split air at the leading edge but provide a clean edge from which the air could release from.

https://robrobinette.com/S2000Aerodynamics.htm

Note how the high pressure (red) bubble sits on top of the splitter adding downforce. The underside of the splitter also generates low pressure (blue) and downforce but the splitter needs to be lower than about 3 inches to generate this low pressure area.

Rebel Front Splitter Insert GB - Cobalt SS Network

Not only will this help stability but it will also help cooling by forcing more air to go through the rads.

Follow the links provided above for proper context, I did not want to Copy & Paste an excessive amount.

EDIT: I sketched up what I think is happening.

Aerodynamics by George Kachadoorian | Photobucket


I would not make it like my splitter, which was an outer lip only - you need a to establish a parallel plane to the ground because your stepped up backer is a step up, and is drawing the air up to fill the vacuum.

Chin Spolier - fast/easy/cheap/effective - Page 2 - Pelican Parts Technical BBS


I have no internal step up on mine shown above, which is maybe why I got away with my design. Yours needs to be different because yours is different.

In other words:
You built an upside down Gurney flap!
(without the splitter/rear deck trunk/wing part)

The chin spoiler is the Gurney flap, second flap is the internal bracing.

http://blog.octanenation.com/kubica-...-thanksgiving/