CASE STUDY
Porsche 996 Ducktail Grilles
Many find the appearance of Porsche's first water cooled 911 a bit bland. One way of addressing this is by fitting an aftermarket ducktail instead of the retracting wing.
This also sheds some weight from behind the rear axle - a win-win situation especially in a car with a rear-weight bias. Unfortunately the grille supplied with this part is typically nothing more than a flat mesh which may be sufficient for a track car but lacks the aesthetic refinement one would expect for an upmarket road car. How do we solve this?
The first step is a high detail 3d-scan
As always, the first step is a high quality 3d scan. One of the interesting aspects of 3d scanning is how it highlights imperfections which can't be seen with the naked eye. In the harsh artificial light of cyberspace every small imperfection, dent and undulation becomes evident, as can be seen in the image to the right. In real life this part was sanded down professionally, painted and polished to a high gloss, and none of this is visible on the car. This makes 3d scanning a valuable tool for car restorers and a nightmare for body shops.
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3d scanning is often used to supplement traditional hand measurements. In the case of an organic shape like this ducktail it is a necessity. There is no other way of accurately measuring the curved surfaces and getting them into CAD.
CAD design
The second step is to design a grille which will fit within the confines of the scanned area. Since the car has virtually no flat surfaces we decided to use curved ribs as the principle design element with thinner, angled vanes running between them. The vanes were angled to be as non-restrictive as possible to the air path into the engine bay. This means that the engine and air inlet are essentially open when viewed from the front but closed when viewed from the rear, which is good to keep falling leaves out.
Manufacturing considerations
The material we chose was carbon-fibre infused nylon-12 which can withstand prolonged temperatures of up to 160C. This is more than any engine grille should ever see unless the car is on fire.
In terms of durability it exceeds regular plastics such as ABS and has the added benefit of being UV resistant and lightweight. Since this is not a stressed part the choice of material is a slight overkill but these parts sometimes find their way onto rally and off-road cars which see a fair level of abuse. So, as always, we cater for the worst case scenario​
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Result
The end result looks aesthetically pleasing and fits in with the rest of the car. These grilles have survived many adventures in harsh conditions as can be seen in the photo collage below. The 996 test mule (which is now living a quieter life in the UK) spent years as test bed for various technologies in South Africa, often in blistering heat and on unforgiving roads.
