You forgot the last sentence in your story:
"Now I'm making one for Joe's Legrand"
You forgot the last sentence in your story:
"Now I'm making one for Joe's Legrand"
If you've watched a Formula 1 race in the past decade or so, you've probably noticed some funny-looking fins below the cars' rear wings. These are called diffusers, and they're simple aerodynamic devices that create a low-pressure area under the car to increase traction. We'd seen them on our competitors' cars in B Modified, so we decided to try one for ourselves.
We began by measuring the available area under the car, as we wanted to fit the largest diffuser possible. The next step was to make a buck (or male mold) out of blue insulation foam. Based on our research, we settled on a few measurements: a diffuser angle of 12 degrees and 5 inches of rise for the 24-inch-long rear section.
Next, we layed up an outer shell for the diffuser. This would form the backbone of the piece and also function as our car's lower belly pan, taking the place of some aluminum sheet metal that was covering the underside of our engine bay. Once the shell was cured, we sanded it down and made strakes and stiffening ribs out of corrugated polypropylene sign material. These pieces were epoxied in place.
After the polypropylene cores were solidly planted, we wrapped them with carbon fiber—essentially making a very light and stiff sandwich. We let that cure, did some more detail sanding, and then finished off the piece with some carbon fiber wrapping around the back edges to make it look pretty.
All told, the piece weighs under 5 pounds. In theory it should help our car stick to the ground, even at autocross speeds.
Would you like to let us in on the "research" part? We'd love to know more!
Reading Simon McBeath's book on Competition aerodynamics and talking with D Sports Racing folks---12 degrees seems to be the maximum angle for a diffuser that can function at lower speeds.
Oh, and from the available space for the diffuser, we then had 1 leg of the triangle and two angles (90 and 12) so we could calculate the rise at the back end.
That's cool! How smooth is the surface finish on that baby? Also, do you think you could snap a picture so we can see how the whole assembly looks like from beneath the car?
It's not molded-smooth--..but not rough either. I'll shoot some additional pics, but more will be published in the more indepth print article.
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