Rear kammback spoiler

[freebeard]

Originally Posted by myself

...the trailing edge of the sail panel, instead of aligning with the bumper cut line, would be essentially vertical and extend to the body crease that bisects the taillight.

Originally Posted by aerohead

I'd advocate that the new 'green' lines extend down to the crease in the hatch,just above where the Ford oval emblem is,enclosing more volume.

Agreed.

[California98Civic]

Originally Posted by aerohead

... the Lamborghini Urus SUV ...

[eagle]

when you suggested that the side winglet should extend all the way down the window , I remembered the toyota glanza rear spoiler(s)

the top one apart from the "ridiculous" angle of attack does come down the window and in many cases, the owners have fitted an additional spoiler tip/lip/tray to the bottom of the windscreen

I always thought this was purely a visual modification but now I am considering it ......a bit.....

thoughts ?

[JulianEdgar]

Just consider the vertical parts as separation edges (ie stopping the flow wrapping around the corners). Plenty of published evidence in support of this approach, and angling them inwards a little (as you previously suggested) is a good idea.

The horizontal extension at the base of the window has a little support in the literature as a possible means of disrupting vortices in the wake.

[California98Civic]

Originally Posted by eagle

when you suggested that the side winglet should extend all the way down the window , I remembered the toyota glanza rear spoiler(s) ... thoughts ? ....

A former EM participant, Greasemonkey, posted a good short thread on a kammback he built for his Civic VX hatch in 2013. He said it more than paid for itself over 80,000 miles of subsequent driving. Here is a photo of the final build. This is I think a good visual approximation of a lot of the advice you are getting.

[freebeard]

Needs speed holes/portholes on the sides, for visibility.

[Fat Charlie]

Not really. It restricts the rear view on a car with an already restricted rear view. The last 6 or 8 inches of the top section are what hurts visibility the most, the sides do practically nothing. On my Fit, the roofline itself does the restricting- I've got to move my head to see around the 3rd brake light.

[aerohead]

Originally Posted by Fat Charlie

Not really. It restricts the rear view on a car with an already restricted rear view. The last 6 or 8 inches of the top section are what hurts visibility the most, the sides do practically nothing. On my Fit, the roofline itself does the restricting- I've got to move my head to see around the 3rd brake light.

It's a good criticism. I do believe that modern synthetic vision will more than compensate for the shortcoming.Driving 'rear-view mirror-less' trucks for over a decade meant, just relying on the side mirrors.
Always scan your environment.

[Fat Charlie]

It was a criticism of the situation, not the mod. A fastbackish roof that isn't a glass hatch is going to restrict visibility. Stretching the roof and dropping the trailing edge a little farther would restrict the view a bit more, but nothing radical: I already have to duck and peek around my CHMSL, I'd just have to do it a bit more

[eagle]

new cars weirdly have these black spots perfect if you want to make a spoiler like the one we are discussing

(the photo is from a 2017 audi a1 but have seen this on many cars, huyndai i30 etc)



also, here is a rear windscreen from a renault scenic with -a quite big - side spoiler which also has these...uhm....holes?