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Fabricating an air dam.
https://slantsix.org/forum/viewtopic.php?t=40704		 Page 1 of 3
Author:  Sam Powell [ Sat Jun 19, 2010 9:09 am ]
Post subject:  Fabricating an air dam.
I was thinking it might be easy to fabricate an air dam starting with an a older pickup truck accessory. Does anyone have a Ford Ranger from 1990-97 that they can measure the width of the bumper on? The Dart measures 62" wide. If the Ranger is that size, there are several nice after market parts for the vehicle that would be a nice jumping off place. Any older pickups with flat front profiles that are out there might be useful also, if they are the same dimension.

Thanks in advance.

Sam
Author:  slantvaliant [ Sat Jun 19, 2010 5:03 pm ]
Post subject: 
I don't have any bumper specs, but I saw this fabricated dam/splitter setup at the Big Bend Open Road Race a few years ago.

Image

Image

Out back, he had this setup:

Image
Author:  zorg [ Sat Jun 19, 2010 5:33 pm ]
Post subject: 
Wouldn't you know it, my dad's '91 Ranger bumper just measured in at 61.5". The bumper appeared to be about an inch wider than the sheetmetal on the truck. Hope that helps.
Author:  Sam Powell [ Sat Jun 19, 2010 7:34 pm ]
Post subject: 
Quote:
Wouldn't you know it, my dad's '91 Ranger bumper just measured in at 61.5". The bumper appeared to be about an inch wider than the sheetmetal on the truck. Hope that helps.
That sounds like about the perfect size.

Slantvaliant, that Dart's air dam is probably highly functional, and nicely done, but a bit much for my taste. It would take some getting used to. That photo is very helpful. Thanks. I know now not to get too carried away. I probably would not take mine down below the level of the sheet metal on the side of the car (rockers).

I know now the Ford RAnger is just about a perfect fit, and there are some simple, tasteful pieces out there. The one I was looking at today has just one hole in each side for what looks like brake cooling ducts. Other than that it was solid all the way across, which means it would actually do something, such as push the air around the car instead of allowing it to create disruptive turbulence around all that stuff that hangs down on the A body cars, such as the K member and Radiator core support.

Sam
Author:  wjajr [ Sun Jun 20, 2010 6:46 am ]
Post subject: 
Check out mid eighties Chrysler Laser & Mustang air dams. Laser came with a very square looking unit not unlike the lower section of the one previously pictured. I think those cars are close in width to an A Body.
Author:  Sam Powell [ Sun Jun 20, 2010 8:00 am ]
Post subject: 
I don't remember what the Lasers looked like. I am goin on vacation today for a week, and I can almost always find a junk yard...er...uh.. auto recycling center to visit. I will be sure to take along my tape measure and a few basic tools.

Sam
Author:  Sam Powell [ Mon Jul 05, 2010 9:25 am ]
Post subject: 
I am finally working on constructing a good functioning, attractive air dam for the Dart. I am pleased with the results so far.I have been thinking about this for about 15 years. No exaggeration. An employee of mine was scrapping his Ford Ranger pick up, and he gladly donated the air dam off of it to my Dart project. It is about an inch short of ideal on each side, but it was free, and I can live with this. It is the perfect depth as it extends down just to the level of the front lip on the K member.

The part I started with includes accommodations for brake ducting which I am building. One side is about done. I am fairing in the underside of the front of the car to make a smooth airflow around the front end parts, all of which will be hidden by the air dam. The fairing will go clear down to the level of the air dam bottom edge between the frame rail extensions that the bumper bolts to to. This means I most likely will cut the bumper open behind the license plate and move the plate over to the right, between the brake duct and the center opening. I think there needs to be a little more opening in the front than just the grill area provides.

The current decision I am wrestling with a bit is whether to have this bottom fairing protrude forward from the bottom edge of the air dam, or end behind it. Does that little lip that sticks out at the bottom of a front air dam do anything at highway speeds, or is it purely to mimic the high speed needs of Nascar?

Now that I am this far into this project, I am wondering if it would be smart to replace the metal bumper with a plastic one? I have always steered away from this out of a basic protective instinct, even though it would save a bunch of weight. I have always been worried some yo-yo (maybe me) would back into it in a parking lot. Does anybody know of a company that produces GOOD plastic bumpers for the 67-69 Darts? I was not happy with the parts I got for the front end. They required a bunch of body work to make them good, and the fiber glass fabric began to show through the paint even though the parts looked flawless when painted.

Thoughts?

Sam
Author:  emsvitil [ Mon Jul 05, 2010 12:37 pm ]
Post subject: 
I thought those rubber lips at the bottom of air dams were sacrifical...

Something to scrape without destroying the air dam.
Author:  Sam Powell [ Mon Jul 05, 2010 1:25 pm ]
Post subject: 
Maybe it would be best to make the bottom fairing of plastic of some kind. I was planning on making if of aluminum. In either event, it will not be anywhere near as low as my Miata. I have to drive that car on 2x4's to get a jack under it. BTW, looking at the Miata design has been very instructional in how to engineer this addition to the Dart. I have it from the Miata forums that if you take that bottom piece off, for ease of maintenance, the temps go up on the engine.

Sam
Author:  Dart270 [ Mon Jul 05, 2010 1:41 pm ]
Post subject: 
Look at some newer car airdams. Usually they are not all the way across, or right at the front of the car. Mine goes straight down from the radiator support front plane, with a little crown (pointiness) in the middle. I know, need to post a pic... It doesn't quite extend sideways to the inside lips of the tires. It is 4" above the ground and it flexible enough to totally distort when I hit things (parking curbs, driveway dip...). I will be revising the design.

Lou
Author:  Sam Powell [ Mon Jul 05, 2010 2:19 pm ]
Post subject: 
Lou, Your description of the design you employed sounds like what I was planning on doing originally. But as I got to studying cars out there on the road, I could not hold the creative juices down. Now I am pretty deep into this. It is not as wild as the photo in this thread, but it does go beyond the simple drop down from the radiator core support.

Mine sits several inches back from the lowest edge of the steel bumper, which makes it recede somewhat from the forward upper part. I wish I could post a photo of what I am doing.

My digital camera has died, or I would snap a photo and send it to you with an e-mail. Send me what you have when you get around to it.


Sam
Author:  slantvaliant [ Mon Jul 05, 2010 4:45 pm ]
Post subject: 
When you have the shape you want and get it mounted, have someone take photos of the dam with the car at speed. Looking at my photos from open road races, it's clear that a lot of the flexible and even some of the metal dams, spoilers, bumper covers and such deflect quite a bit just from aerodynamic forces. This even happens in the slower classes, say, 85MPH. Reinforcement might be in order.
Author:  Sam Powell [ Mon Jul 05, 2010 7:42 pm ]
Post subject: 
Quote:
When you have the shape you want and get it mounted, have someone take photos of the dam with the car at speed. Looking at my photos from open road races, it's clear that a lot of the flexible and even some of the metal dams, spoilers, bumper covers and such deflect quite a bit just from aerodynamic forces. This even happens in the slower classes, say, 85MPH. Reinforcement might be in order.
That is good to know. This will influence my decisions from here on out. I guess you have to make a choice between strength and flexibility. One is good for performance reasons, the other is good for "OOPS"! reasons. I know I have dragged the front of my Miata over quite a few parking stop blocks, and was glad I decided NOT to paint the air dam. And it's flexibility has saved it for sure.

I guess if I make the Dart's bottom fairing strong, as in out of Aluminum, with good bracing, I will have to be extra careful where I take it, and over what terrain.

Does anybody know what is the best way to handle the underside of the rear of the car? It is pretty clear from looking at present day designs what they are trying to do with the front, but I cannot tell what the guiding principles are for the rear of the car. Could you fair in the bottom of the car and get any improvement? And, how about the bottom of the car itself. Do the cross members catch air and create turbulence that is disruptive?

Sam
Author:  oldblue [ Mon Jul 05, 2010 8:43 pm ]
Post subject: 
Check out some of the info here.http://ecomodder.com/forum/aerodynamics.html
Author:  Sam Powell [ Tue Jul 06, 2010 5:37 am ]
Post subject: 
That is amazing, Oldblue! One could spend hours reading there. I already spent one hour. It is hard to relate this stuff to our old squared off body styles, but the basic theories are there to work with. One could really get sucked into this kind of thing as an entirely new hobby. I am already thinking about my design and how to change it.

One thing to note, some of the experiments conducted by these forum members were pretty ugly. I would not have the heart to go anywhere near that route. But, tasteful mods can be made to make some improvement for sure. Thanks again.

Sam
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