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Old 05-11-2018, 07:42 PM   #1 (permalink)
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Kammback question

My computer is down and I'm not sure how to upload pics from my tablet so please bear with me.

I have seen newer vehicles with a Kammback (if that is the right word) spoiler mounted along the roofline above the rear windows. Some are flatter (like a Jeep Cherokee) and some are more "curled" with what I can only describe as inverted winglets (like a Ford Focus). I have seen the chart showing truck bed aerodynamics and wondered if I could adapt something from another model vehicle to the cab of my Ranger. I already have a tonneau cover and the chart showed a pretty significant improvement with the addition of a spoiler.

The question is what type spoiler would I look for? The flat style or one with the downward curved edges?

It'll be a small miracle finding something that fits the shape of my cab anyhow, so it may be a moot point. I'm thinking the flatter style would be easier of the two to adapt though.

Any thoughts?

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Old 05-11-2018, 07:54 PM   #2 (permalink)
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In theory, flat spoilers on both the top of the cab and the sides, angled slightly inward(5* or so) with about a 1” gap between the cab and the spoiler would be ideal, as it would start the air in the shape of an aero-shell...
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Old 05-11-2018, 09:16 PM   #3 (permalink)
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I had started to build an aero cap for my old Ranger (the '97) and had worked out all the angles pretty well. IIRC it was about 3-4 degrees at the edge of the cab to most closely fit the template. Then up to about 7 degrees and then 12 degrees to the tailgate.

This old thread has some of the pics. Never got a chance to finish it and now the Little Black Ranger it gone.

Advice on aero-cap shape
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Old 05-11-2018, 10:39 PM   #4 (permalink)
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One thing, A spoiler is different from a wing. A wing works on the difference between the air pressure above and below the wing. A spoiler "spoils" the lift created by air being stretched over the top of the car, usually by redirecting the air away from the horizontal.. I prefer a wing, and if possible, one that can raise and lower when needed or not.
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Old 05-11-2018, 11:42 PM   #5 (permalink)
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kammbacks and roof spoilers

So here is the Jeep Cherokee spoiler, not very much like a kammback:


And here is a kamm style roofline spoiler on the back of a Focus:


Whether either is what you want is hard to say.

What you do in fact want is a spoiler that brings your general shape closer to "the template," which looks like this:


Overlay that template on a good profile shot of your vehicle, probably by finding on online. Align the point of highest camber on the template with the point of highest camber on your vehicle photo. Then your roofline spoiler shape will emerge.
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Old 05-14-2018, 11:18 AM   #6 (permalink)
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Quote:
Originally Posted by hat_man View Post
My computer is down and I'm not sure how to upload pics from my tablet so please bear with me.

I have seen newer vehicles with a Kammback (if that is the right word) spoiler mounted along the roofline above the rear windows. Some are flatter (like a Jeep Cherokee) and some are more "curled" with what I can only describe as inverted winglets (like a Ford Focus). I have seen the chart showing truck bed aerodynamics and wondered if I could adapt something from another model vehicle to the cab of my Ranger. I already have a tonneau cover and the chart showed a pretty significant improvement with the addition of a spoiler.

The question is what type spoiler would I look for? The flat style or one with the downward curved edges?

It'll be a small miracle finding something that fits the shape of my cab anyhow, so it may be a moot point. I'm thinking the flatter style would be easier of the two to adapt though.

Any thoughts?
maybe there's something about this in the seminars.
In 1988,Texas Tech University published an SAE Paper based upon research they did with Ford pickups.Both CFD and full-scale tunnel testing at Lockheed,Marietta,Georgia.
Different cab-'wings' were tested in combination with a half-tonneau covers,and the lowest drag configurations were a function of bed length,wing length,and wing angle.
At the sweet spot,you could get an 18% drag reduction.
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Old 05-15-2018, 09:55 PM   #7 (permalink)
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Thanks everyone.

Aerohead.....when you say "....in the seminars..." what do you mean? Is there a section of the site I haven't explored yet? I would love to read more and try to learn more. If I decide to try something like this I probably won't change the tonneau to a half tonneau.

What I would really like to do is rework my old aero cap that I linked to earlier and adapt it to the new truck. The original cap was for a short bed stepside. The new truck is a regular bed fleetside. Time is at a minimum right now with work and the drive to and from. I still like the cab/wing idea though. It's amazing how easy things work in your mind.
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Old 05-16-2018, 09:40 AM   #8 (permalink)
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I put a roof wing on my S-10 and it's flat, no angle.

There is a slight air gap between it's leading edge (beveled down 45 degree angle) and rear of the cab's roof edge.

It works to provide some down force via the air slot going off the seat of my pants feeling.

The thin sharp edge of it's end is a clean release edge for the air.

If I were going to adapt an SUV roof spoiler I'd look for one that's a bit neural looking in it's angle, maybe slightly downward and has an air slot.

I took photos yesterday of the only SUV with roof spoiler that directed the air upward, but it was just at the two ends as if to purposely induce a vortex. I'm sure that is a model specific solution from many hours of wind tunnel testing and perhaps would avoid it. I will try to post the photo later.
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Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
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Old 05-16-2018, 06:31 PM   #9 (permalink)
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Happy hunting.

I like kach22i spoiler for the crescent-shaped back edge. I'll be it makes pretty vortexes under polarized light.
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Old 05-17-2018, 11:47 AM   #10 (permalink)
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Quote:
Originally Posted by freebeard View Post

Happy hunting.

I like kach22i spoiler for the crescent-shaped back edge. I'll be it makes pretty vortexes under polarized light.
That design has been CFD illustrated by two different people, one of them a professional and that wasn't an issue.

The wheel openings and Sportside bed however were very dirty looking.

FYI: The SUV rear roof spoiler I spotted the other day was a Santa Fe by Hyundai.

The two return ends follow the side arc roof line down.

The middle part where the rear hatch is slopes at a greater angle downward.

The transition between these two angles makes an optical illusion that the the ends flip up.

I was able to take a close look at this while out running, sorry no pictures.

Click the link and zoom in.
https://rwshiftinggears.wordpress.co...ndai-santa-fe/

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1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
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