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Old 10-02-2016, 02:37 AM   #1 (permalink)
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Lip spoiler?

So, I've been pondering the aerodynamics of my Malibu again(always seeking gains), and I'm working presently on a lip spoiler... Right now, I've got my old vortex generator array repurposed into the inner reinforcement for a lip spoiler... The thing is, I'm not sure how to optimize the design for aero benefit... Right now, the reinforcement is made up of triangles, roughly 1"x2", right triangles, meaning the spoiler rises at roughly a 30* angle, and has a hypotenuse of roughly 3"... The thing is, the trailing edge of the trunk is curved, and I would like to match it... Either I can curve the entire spoiler and complicate the build with a complex curved hypotenuse, or curve just the trailing edge of the spoiler, making it taller(and longer) in the center, and shorter near the edges...

Is a 30* angle suitable for aero, or should I change it now, before gluing the entire thing together? What would be the optimum height for it?

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Old 10-02-2016, 01:23 PM   #2 (permalink)
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I thought those were for rear down force not slipperiness. My L200 has the flat type spoiler on the trunk lid, I don't know if it is just for looks or if it helps.
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Old 10-02-2016, 01:57 PM   #3 (permalink)
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I think that the spoiler changes the effective rear glass angle, making the profile closer to the Kamm-back shape... If it also extends past the end of the trunk lid, it can also help with the fineness ratio... The one on my wife's Impreza isn't too tall, but it does extend past the trunk lid for nearly an inch, and Subaru chose to put them on all the 15-up models(even my wife's 2.0i base) for an improvement of (supposedly) up to 1mpg highway...

Which kinda straightens my perspective; I think my spoiler may end up too tall, so I might reshape the triangle reinforcements for a lower height and try to elongate the hypotenuse surface past the end of the trunk lid...
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Old 10-02-2016, 02:54 PM   #4 (permalink)
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Can you put numbers on, or show a picture of, that curve? And what's the goal? Keeping the rear wheels planted or squeezing out more mileage?

Gurney flap (or wickerbill): small in scale, at right angles to to 'trip' the airflow locally.

'spoiler' spoiler: same scale as the rest of the car. I like to think of it as a fence that prevents the wake migrating up onto the decklid where it can suck on the back window.

Bonneville spoiler: flat and long. Benefits as you describe. It can also be the top of a box cavity:

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Old 10-02-2016, 09:46 PM   #5 (permalink)
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I'll grab some pics tomorrow of the curve, but the idea is to get better mileage from its addition, not so much for downforce... A bonneville type spoiler would help fineness ratio, and promote detachment, but for some reason, I'm hung up on something like the Malibu SS had... It looked pretty cool...
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Old 10-08-2016, 01:48 PM   #6 (permalink)
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30-degrees

Quote:
Originally Posted by 19bonestock88 View Post
So, I've been pondering the aerodynamics of my Malibu again(always seeking gains), and I'm working presently on a lip spoiler... Right now, I've got my old vortex generator array repurposed into the inner reinforcement for a lip spoiler... The thing is, I'm not sure how to optimize the design for aero benefit... Right now, the reinforcement is made up of triangles, roughly 1"x2", right triangles, meaning the spoiler rises at roughly a 30* angle, and has a hypotenuse of roughly 3"... The thing is, the trailing edge of the trunk is curved, and I would like to match it... Either I can curve the entire spoiler and complicate the build with a complex curved hypotenuse, or curve just the trailing edge of the spoiler, making it taller(and longer) in the center, and shorter near the edges...

Is a 30* angle suitable for aero, or should I change it now, before gluing the entire thing together? What would be the optimum height for it?
Back in 1974,CAR and DRIVER experimented with some home-built spoilers for their CRISIS FIGHTER PINTO project.They found a drag minimum when the rear spoiler had a 30-degree up-sweep.
Some have done like you're thinking about,using the spoiler to reach up to the template profile
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Old 10-08-2016, 05:30 PM   #7 (permalink)
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Well, I'm probably not gonna reach that high with the spoiler, as I plan on a hypotenuse surface length of 3-4", but it should help at least a little
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Old 10-08-2016, 07:59 PM   #8 (permalink)
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The first-gen Civic Hybrid had a small spoiler on the rear of the trunk that was supposed to be good for a reduction of ~0.02, if I recall correctly.

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Old 10-08-2016, 08:21 PM   #9 (permalink)
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Quote:
Originally Posted by aerohead View Post
Back in 1974,CAR and DRIVER experimented with some home-built spoilers for their CRISIS FIGHTER PINTO project.They found a drag minimum when the rear spoiler had a 30-degree up-sweep.
Some have done like you're thinking about,using the spoiler to reach up to the template profile
What car is that?

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Old 10-08-2016, 08:56 PM   #10 (permalink)
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Quote:
Originally Posted by Ecky View Post
The first-gen Civic Hybrid had a small spoiler on the rear of the trunk that was supposed to be good for a reduction of ~0.02, if I recall correctly.

I think my spoiler will end up being taller than the HCH1 spoiler, if I extend it past the end of the trunk lid, and keep my approx 30* upsweep... Ideally, I woulda just bought the factory spoiler from a Malibu SS, but I've yet to find one, and really don't wanna spend $40-60 on one...

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