Rear hatch airflow/spoiler idea

"Echo51" (echo2047) 02/06/2016 at 15:52 • Filed to: None

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So i own a hatchback. I did away with the stock spoiler to get a bit more downwards rear-visibility, and also deleted the wiper because a loner wiper never looks nice. Now i have water droplets forming on my rear glass, and even with 50mph they refuse to budge or run off, so clearly there’s a pocket of stagnant air there. Would a roof spoiler be able to create some turbulence or other air over the glass so it would blow clean?

(Shown here on a FR-S with/without roof spoiler, it looks as if it has some air movement against the glass?)

Here’s my car in question.

Berang > Echo51 02/06/2016 at 16:04

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The Saab 95 had a spoiler that was designed to clear the rear window. You can see a slot in the top that directs air downward under the spoiler and over the rear window. The early car on the right lacks this feature.

AddictedToM3s - Drives a GC > Echo51 02/06/2016 at 16:09

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I would believe a roof spoiler would create an even more predominant pocket of air over the rear window making the rain drop situation worse. Using that same train of thought though, the vortex generators found on the Evos would create the effect you are looking for? Although I could be very very wrong.

Echo51 > Berang 02/06/2016 at 16:31

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I was thinking something along this aswell, to direct air down along the glass, just been unable to find any pictures of what i was thinking. Thanks!

Echo51 > AddictedToM3s - Drives a GC 02/06/2016 at 16:48

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Interesting, and seems worth a try too. Combined with wool-tufting to see the flow aswell. Maybe tape up the roof to hatch gap?

http://www.autospeed.com/cms/article.ht…
If all else fails i may have to take the random internet forum posters advice and just drive with the tailgate up!

TheRealBicycleBuck > Echo51 02/06/2016 at 17:31

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They used to be common on minivans. It grabs a little air and redirects it over the rear glass. I'm not sure they were very effective, especially at low speeds.

Eric @ opposite-lock.com > Echo51 02/06/2016 at 18:21

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In the case of the FR-S, the spoiler is making it worse. It’s creating a pocket of low pressure above the rear glass.

It would be possible to direct air downward, but it would negatively affect handling and/or fuel economy.

Try putting Rain-X on it so it rolls off.

Echo51 > Eric @ opposite-lock.com 02/06/2016 at 18:27

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I had something similar to Rain-X before, and that just made the droplets smaller, making it even more opaque. But you could get it to bead together and roll off by either accelerating hard enough to make the roof water roll down over it.

Levitas > Echo51 02/07/2016 at 00:04

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I’m about to finish up a second degree in aerospace engineering, so I’ll offer a few cents:

What is being shown with the FR-S is actually reversed flow (the boundary layer separated) coming back up the window. If you had the droplets on it, the drops would actually be driven up towards your roof. The reason the little wing is added is to create that little pillow of reversed flow, which then works with the little trunk spoiler, which then reduces the size of the wake behind the back of the car. Believe it or not, but it actually improves aerodynamics and lowers drag!

So, for your car, you could do what others have suggested, and mount a flap/wing that pulls air and directs it more tangential with the window. This should work, but might add some wind noise and some drag. Other than that unfortunately, you’re kinda out of luck because of the inherit shape of the vehicle.

Echo51 > Levitas 02/07/2016 at 04:57

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Cheers for the input. If all else fails i’ll just have to start driving with a glass scraper or something else to wipe it off it bothers me.

Jdrentarol > Echo51 02/11/2016 at 10:08

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Go for it

Echo51 > Jdrentarol 02/11/2016 at 10:12

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Might aswell go for the actual Cossie wing for the escorts then :D

Jdrentarol > Echo51 02/11/2016 at 10:16

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Goddamn I want a wing from that car- just so I can mount it on my wall and stare at it.