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Old 12-15-2020, 02:50 PM   #30 (permalink)
JulianEdgar
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Quote:
Originally Posted by woodstock74 View Post
While I'm at work and don't have access to pictures...I've been contemplating a small modification to my spoiler which I'll try to describe without pictures. So trailing edge sharpness is an obsession for me, maybe it's important, maybe not so much. But aero details on road cars are detuned to avoid pedestrian issues (and manufacturing practicalities I'm sure). I've been wanting to add a trailing edge extension to my spoiler (the old spoiler didn't survive the rear ending, see pictures further up in thread, and they replaced it with a proper factory spoiler) that essentially redoes that work, but also angles down slightly. So it would be an extension, not merely a sharpening of the existing trailing edge, perhaps 60 mm in length, angled down approximately 10 degrees from the trailing edge of the base spoiler. Curious thoughts on this? The idea is all about base area infill of course, and it would have a sharpened trailing edge to boot increasing turbulent kinetic energy as the airflow snaps off that edge. Or should I just concentrate on giving the existing spoiler a shaper edge (it's rather rounded)? Nothing pedestrian-slicing of course, the end part would be FDM 3-D printed.
A few points:


- Trailing edges don't have to be sharp sharp to work, so I wouldn't obsess over that.

- If you "increase turbulent kinetic energy as the airflow snaps off that edge" you will likely make things worse, as I would think that the trailing vortices will be more intense. (That's not how separation edges work.)

- I think the notion of "base area infill" is a bit deceptive, as I don't think you can easily do that. What you can do is reduce wake size - not quite the same thing.

- An angled downwards rear extension probably will reduce wake size and reduce drag, but you'd find out only through testing whether it was worth doing. Test first with a mock-up of plastic sheet!
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