Hey guys. I've lurked these forums for some time, and now I'm posting because I recently bought a 2006 Jetta TDI and I'm really interested in this type of spoiler. I put together a couple of images of what I envision and I'd like to know what you guys think.
This design is similar to California98Civic's, but it will be a bit longer and with larger vertical fins. I feel the fins are important for two big reasons: one, I want to isolate the "bubble" behind the car as much as possible, which should create some sort of virtual boat tail and promote cleaner separation. Two, and probably the most important: this spoiler separates two very different air masses - fast moving air on top, and stagnant air on the bottom. That stagnant air will want to push its way around the spoiler toward the low-pressure stream on top (which, I'd like to note, makes me think this spoiler actually creates lift), and these fins should prevent that from happening. I don't claim to be an expert, so I'm open to suggestions if anyone disagrees with my logic.
Now, here's my idea. Rough math puts the spoiler at being around 30 inches long at a constant 13.8 degree slope. I'm sure I'll have to do some tuft testing to ensure that the boundary layer stays attached, but I think it seems plausible. I'd like the trunk to be functional with this thing on it, so the vertical fins will conform to the back of the trunk; the rear-view picture should give you an idea of what I mean.
In these pictures, the spoiler is red and the vertical fins are blue. What do you guys think?
P.S. Laws in my state dictate that I can have extensions as long as 6 feet on the rear of my car, so I'm good on that end
