| The Protar 1/24 Lancia LC2 that I'm building is a primitive kit, with many details that cry for improvement. I decided to take the louver panels over the front wheels as a good subject to try to design and print new parts for. |
| A clear photo, showing six slots, with the louvers raised. I think I've also seen the panel inverted, with the louvers projecting down and forward.
The louvers are all of equal length, note how they 'cross' the dark blue Martini stripe on the inboard side. | 
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| This photo shows the same configuration. It also shows much clearer that the inboard edge of the louver panel is angled, it almost follows the dark blue Martini stripe. |
| An excellent overall view of the car, and the front wheel louvers. I used it to calculate the louver panel length as a percentage of the wheel base. | 
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| A similar view of the Mirabella car. It allowed another measurement of the louver panel length. |
| In yet another study, I connected the ends of all louvers, to see whether they are a straight line or not. To my surprise, the inboard ends are not on a straight line, their length decreases towards the rear of the car. | 
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| I made a single louver component, by lofting through several side-to-side cross sections. A window frame defined the panel shape.
Note the thickness of the parts. This is always a gamble: how thin can you go? It usually looks massive on screen, but very acceptable once printed. | 
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| The louver was multiplied, and mated with the window frame, creating a louver panel. It's not the definitive panel, since it has 5 instead of 6 louvers, and a rectangular panel. But it would a good test piece to print. |
| Here's a view of the STL export, that looks smoother. I refined the design a bit, making the louver 'lips' 0.3 mm whereas the rest is 0.6 mm. Another area of improvement is that the louver facets are now slightly shorter, and the opening angled away from the 'vertical'. It implies that the sheet metal was only bent, not stretched. | 
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| Initial printing attempts failed miserably, and this was the best one! Shown here is an 0.3 mm thick design, that came out as 0.2 mm, with printing flaws: holes and warping. They would be near impossible to separate from the supports without snapping small chunks from the actual parts. That's why I learned later to add the support manually in the slicing software. | 
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| I finally got a near-perfect print. But my design was not: it has 5 louvers, and I now count 6 louvers.
While studying reference photos, I noted that one car (0007 in 1985 configuration, as sold by Girardo & Co in 2020) had the six-louver panel mounted upside down - interesting! |