Winglets and bumpy paint? - Fuelly Forums

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Old 05-19-2007, 04:06 AM   #1
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Winglets and bumpy paint?

Winglets:

Has anyone experimented with winglets in front of wheel well openings? Using my hand propane torch and some vinyl, I've formed winglets.

Since I have to drill visible holes to mount them, I thought I'd try to get some actual data before I start drilling holes willy-nilly.

Bumpy paint:

I cover a lot of air shows. In the mid '80s, I was able to get up close and personal with a MIG-29, the Russian F-15 clone. Now, these things can go mach 2 but the Russkies had a problem. They can't build a quality aircraft skin to save their lives. So they came up with a unique approach to allow the plane to slip through the air. Bumpy paint. A urethane coating that looks like it has large grains of sand in it was applied before the paint to create a "zone" of separation between the poor fitting panels and the air stream. I was able to have a conversation with the designer who was touring with the aircraft(s) around the United States who was somewhat forthcoming with the information after being plied with some compliments about the MIGs. Photos of MIG attached; note bullet holes in tail.

Just a thought.
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Old 05-19-2007, 04:47 AM   #2
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Ah, speed holes!
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Old 05-19-2007, 05:46 AM   #3
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Explain what you mean by winglets. Do you mean deflectors? (Check the aero discussion forum - I posted a thread about them with a pic of the Tesla's deflectors.)

As for special paint / dimples etc., everything I've read about automotive aero on this topic says that at typical speeds, this type of thing makes no appreciable difference.
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Old 05-19-2007, 06:07 PM   #4
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Here's the a photo taken from the video.

Think canard instead of winglet. Just another little thing to get the air away from the front wheels at speed.
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Old 06-01-2007, 09:28 AM   #5
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There are a number of studies that support small "air dams" or deflectors in front of the wheels on the bottom of the car. Additionally, the C6-Z06 Corvette has small "Gurney lip" spoilers on the front edge of the front wheel well. It stands to reason that getting the air around the wheelwell will lessen turbulence, and therefore, drag. Interestingly, the small lower "air dams" actually increase frontal area of course, but directing the air around the tire and wheelwell more than makes up for the drag penalty.

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Old 06-01-2007, 02:01 PM   #6
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Without adding any frontal area, one could stop the straight on collision of the air flow and the tires by using a small deflector... it will help but the criteria should be: direct more air outside rather than more inside/underneath the car, do so in such a way as to complement any streamlined flow existing on the car's perimeter (like smooth exstension of lower fender/lip), and make sure it isn't so low that it will rip off/bend on the first pothole or speedbump..

Don't expect to be able to measure the change though. it will be too small, but this and a few other small changes could shave a 1 or 2 or 3 off CD and you will eventually notice.
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Old 06-01-2007, 07:55 PM   #7
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The canards in front of the front wheels works. I notice the most difference when in traffic. What I've done so far retains the mpg at higher speeds. It's installed just above the air dam. I'm debating the same thing in front of the rear wheels, the pre-2000 wheel wells (the pre 2000 Dakota had an aero fender flair front and rear that extended the wheel wells past the tires) or a combination of disc wheel covers and a rear skirt. Figure $10 for canards, $300 for the flairs and $200 for the disc/skirts.

My issue at this point is that everything I've added (with the exception of the side skirts) is attached to the front bumper fascia which is plastic. Now I'm faced with drilling metal which is rather permanent in "damage".

I'll have video of the canards in a few days; I'm going into post-production of my next episode this weekend.
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Old 06-02-2007, 12:38 AM   #8
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hmm same principle applies to golf balls... they dont go mach 1...might as well try it...
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Old 06-02-2007, 03:53 AM   #9
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You could use the "stone chip" coating that manufacturers put at the bottom of some vehicles; that's pretty bumpy. But would the entire vehicle need it? If I recall, the entire airframe wasn't coated, just the leading edges where the ill fitting panels were. It was a long time ago and I wasn't allowed to shoot close up photos, just the long shots.
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Old 06-02-2007, 08:56 AM   #10
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There's a few articles on the web documenting how auto surface conditions basically do nothing for aerodynamics. This makes sense to me after all of my digging. Dimples on golf balls work, but the same correlation cannot be made on larger surfaces due to different aerodynamic effects (flow separation is partly a function of surface length.... a not often quoted fact is that small scale wind tunnels do not accurately reflect full scale unless the pressure in the wind tunnel is increased corresponingly). For the vortex jets and maybe the rougher surfaces on planes and jets... the velocities are so much higher that things like that can make a difference.

For a car, 20 feet long at 60-80 miles per hour, neither would likely have a measurable effect... you need to affect the air flow more dramatically than you can with such passive means. Look up synthetic jets however. These look more promising if you are looking for something measurable, yet not altering of vehicle shape characteristics in a large way.
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