There are times when both passion and logic influence a decision in equal proportions. Alfaista Mike Cudahy wanted to go racing. He'd been driving an Alfa Romeo Duetto in local club events and had the bug. He wasn't excited about the safety provided by an open car, so he began looking for a closed car—logic. Cudahy also loves Alfas—passion. So, when an Alfetta came available near him, he went to look at it—passion. It was perfect for a racecar project. It had a blown motor, worn out interior, and straight body panels—logic. He brought it home.

"I chose the Alfetta GT for a couple of reasons: One, simply because I've been a fan of Alfa Romeo cars since before I had a drivers license. Two, because it provided an interesting platform, in that virtually nobody was running the car in any of the classes. This meant that I had access to an empty canvas in which to create a competitive car by using whatever talents I had, or had access to. It's much more of a challenge to make a car competitive on your own than it is to write a check for someone else's fast car. I wanted to do more than win; I saw it as an incredible opportunity to create, to design, to learn."

His second chore was to decide in which class to race in the Sports Car Club of America. The Alfetta could run in SCCA's ITB, under Improved Touring rules, or it was also eligible in E Production as a Full Prep car. He has a STRONG propensity for tinkering, so he figured the EP would be more fun—passion. Since he is a prototype model manufacturer, he also had some ability to tinker—logic.

The Alfetta is not exactly the hot choice for EP. It is a bit heavy, not terribly aerodynamic, and, with its 2-liter engine, not a powerhouse. Cudahy had his work cut out for him. But he had some thoughts about how to reduce drag and improve downforce. A friend from the Rapid Prototyping Consortium at the Milwaukee School of Engineering (MSOE) reminded Cudahy that the school had a wind tunnel and senior engineering students looking for an interesting senior project. Cudahy had graduated from MSOE and was familiar with the technology they had available, so he approached Dr. Robert Kern about making aerodynamic improvements to the Altetta a senior project. He was soon involved as an advisor to Mechanical Engineering students Nicholas Kristan and Rick Williams, who were excited not to be doing a project that was purely theoretical. A side benefit was that Williams brought some useful and practical experience to the project—he had been a body man for eleven years before pursuing his degree. The final report for their ME 492 Senior Design III project was titled "A Lighter and Faster Alfetta GT" and provides the details for this article.

When starting a project like Cudahy's, it is important to have some measurable outcomes so you know when you have been successful. One important measure was the weight. The rules say that an Alfetta can weigh 2000 pounds; Cudahy's car weighed 2108. So, a primary goal was to reduce the car's weight by 108 pounds. Usually that's easy, since all you have to do is replace steel with lighter materials where the rules allow. The driving goal, though, was to reduce the weight in a way that also improved the aerodynamics and downforce of the car, a good thing to do with a car that already suffers from power deficit.

The approach to aerodynamic improvements and weight reduction centered on redesigning the front and rear quarter panels, header panel, and spoiler. Taking advantage of the rules that allowed for flares to accommodate increased track, new panels would he fabricated from carbon fiber to provide the weight savings.

The wind tunnel at MSOE wasn't one that could accommodate a full-size racecar, so the plan was to make a scale model of the car. Ideally, the model would have resulted from a laser scan of the racecar, giving a very accurate computer image of the car. Cost being a consideration, Cudahy bought a 1/43-scale model Alfetta, which was then scanned. The scale model was produced from the computer image at a 1/17.2-scale using Laminated Object Manufacturing (LOM). In their final report, Kristan and Williams describe LOM as "a process where a laser cuts the perimeter of a part from sheets of paper (layers of paper glued together) along with a grid between the border and part line. The part is then carefully uncovered by removing the small pieces of the grid, sanding and covering (the part) with a finish to protect the model from humidity." Essentially, the model was a block of carved paper covered with a hard finish. Imperfections were smoothed or repaired using modeling clay.

The scale, 1/17.2, seems an odd number, but it was determined based on restrictions on how wind tunnels can be effectively used. A model cannot exceed 7% of the tunnel's cross-section, or it will cause "tunnel blockage". The model of the original car had a frontal area, calculated using SolidWorks CAD engineering software, of 0.05507 sq ft; and the altered body style's frontal area was calculated to be 0.06223 sq ft. The 1/17.2 scale was selected because it produced a model that was big enough to work with but still less than the critical 7% of the wind tunnel cross-section.

Once painted and with wheels added, the "stock" model was tested in the wind tunnel to establish the base number for drag. The wind tunnel set up was designed to elevate the model and move it out of the effects of the tunnel's lower boundary layer. Drag was measured from a spring scale connected to the bottom of the model by fishing line run over a friction-less pulley.

The aerodynamic improvements for drag appeared to be quite good. In order to decide on what alterations to test, Cudahy had looked at the shapes of a number of altered Alfetta racecars. These included a number of cars raced successfully in Europe. But Cudahy also made sure he understood SCCA's "General Competition Rules". This is a critical step in any race-car development process. If you don't understand the rules, you are going to have a very unpleasant season in the tech shed. The aesthetics of the shapes he reviewed (passion) and the reality of the OCR requirements (logic) produced the prototype shape to test.

With the potential shape selected and the test procedure designed, it was time to run the tests. After the model was mounted in the wind tunnel, temperature and atmospheric pressure were recorded, since you can't compare data from multiple tests if the ambient conditions, which can vary considerably, arc unknown. The tunnel tan was then brought up to 50-Hertz (1Hz=1 cycle per second), drag force recorded from the spring scale, and wind speed measured using a Pilot-static tube. The runs were repeated at IHz intervals until a fan speed of 60Hz was reached. This entire process was repeated three times, for both the stock body shape and the racecar body.

The final results of the tests showed that, when drag force was plotted against velocity, the altered body had a higher drag force at lower speeds than the original, but that the force on the stock body increased more rapidly than that on the altered body, finally resulting in a lower drag force on the racecar shape at the maximum velocity of the wind tunnel. Higher drag on the racecar body shape at lower speeds is likely related to increased downforce, which is a good thing when cornering.

Downforce measurements were made during the fabrication of the new body panels, because downforce improvements, while important, were secondary to weight reduction and aero-improvements. The set up for measuring downforce was innovative but not very successful. A false floor, similar to the one used for the drag measurements, was constructed, but it was allowed to rest, through narrow slots cut in the wind tunnel floor, on its wheels on a scale. The results showed that the new body shape had more downforce initially at low speeds, and then both body shapes produce similar downforce as speed was increased from about 67-72 ft/sec. Above 72 ft/sec, the new shape had less down-force than the original shape, the result of improved airflow over the more aerodynamic body shape. At the highest fan speeds, approaching 80 ft/sec, downforce on both bodies was again the same. While the data looked reasonable, an analysis of the test procedure suggested that they couldn't be trusted. It was feared that the negative pressure created by the moving air inside the wind tunnel, and causing an uneven distribution of force on the model, was too much for the model to overcome. The results, therefore, were questionable. A more accurate procedure was devised, but the reality of an approaching race season prevented the procedure from being tested.

After validating the performance of the new body shape, the next step was to produce new body panels for the racecar. To help the process along, Cudahy bought another Alfetta to use to construct the buck from which the molds for the new panels could he taken. Kristan and Williams reported on this process in their final report: "By using aluminum templates and Styrofoam, the new design features were roughly shaped on the duplicate car. Application of polyester body filler and grinding to desired shape resulted in the final design. Once this was complete, the panels were painted for a smooth finish so that molds could be taken." This was quite a time-consuming process, since imperfections in the buck would show up in the molds and, therefore, the new carbon fiber body panels. The finishing process involved priming, sanding, and waxing the surface to make sure it was very smooth. With one side completed, cardboard templates were cut for several sections of each panel. "The sections were then used on the opposite side for an identical match." The final step was to spray the surfaces with polyvinyl alcohol; a treatment that made it easier to remove the mold once the mold material had been applied and hardened.

The mold material proved to be another critical piece of the project. It needed to he easy to use and relatively inexpensive. Cudahy's business, Prototype Techniques, builds prototypes, so he was familiar with the materials that were available. He settled on Epopast 400, a molding material that is easy to use, good for five or six sets of body panels from each mold, and costs about $120 for a mold. Axson North America, Inc., produces it, and one of Cudahy's sponsors, Thyssen Krupp/AIN Plastics (800-544-0597) who distribute AXSON Epopast 400, provided the material for the project. According to Cudahy, "The AXSON Epopast 400 laminating epoxy paste gave us all kinds of advantages: It's very inexpensive, it's really easy to use, kind of like playing in the mud at kindergarten, and best of all, gives you a useable mold in 24 hours!"

Cudahy's season with his newly modified Alfetta included many of the problems associated with racing a newly modified car, hut the overall results of the project were positive. The handling and down-force of his lightened racecar were noticeably better with no effect on the car's top speed. Even with the increase in frontal area, the newly designed pointy end of the car helped keep the car's nose planted better on the track. Alfettas, with their high front end, develop lift at the front because they channel air under the car. The new design directs the air over the hood of the car and around its wheels, improving aerodynamics and downforce. The results were quantified at Road America, where Cudahy's lap times dropped two seconds a lap with the reshaped car. His results this year were better than they had been, but the Alfetta is a big car with less power than many of the EP rivals, so Cudahy remains an underdog in the class. Sometimes, though, you just have to go with your passion.

(ALFA OWNER May 2004 PG.11)