This week, I continue to work on the various brackets used to support the horn grill and turn signal housing found on the desirable longhood models from 1969-1973. In addition to the brackets under the headlights, my car needs the formed patch panel to bridge the gap between the fender wheel arch and the turn signal lens. In other words, I’m talking about how to form a patch panel that replaces the accordion bellows famous on the impact bumper cars. (pic below)
A streak of creative thought inspired me to form my own a patch panel. This patch panel needs compound curves and radiused flanges to match the factory longhood wheel arches. Not only does the earlier Porsche longhood look better in my opinion, but it will also weigh less.
How to Form a Patch Panel Using a CNC Machine
Since the small patch panel is a convoluted shape I decided to make a hammerform using a CNC machine. First, I traced cardboard templates from an original longhood car. Then I scanned my traced templates into 2D images using a flatbed office scanner. I imported these curves into CAD software to create the desired 3D surface. Next, I created the tooling paths for the CNC machine and viola!
A body hammer and simple nylon block ended up being the best tools to hammer the shape into the form. Extra care with the hammering ensured I didn’t dent or damage the wood form as I pushed the metal around. You can hear when the metal has bottomed out on the hammerform. In summary, I’m really happy with the final contour match and can’t wait to weld it in place. If you have any questions or would like to see more please let know.