Dimpled vinyl wrap more efficient than paint?
Know why golf balls sport their dimpled finish? That uneven surface cuts wind resistance, allowing the little objects to fly further through the air. Similar technology has more recently been applied to athletic garments like the oufits worn by Olympic swimmers and cyclists. Could the same principles also apply to automobiles? At least according to a new venture called FastSkinz, the answer is yes. This company's recent development by SkinzWraps, a firm that specializes in vinyl wraps for automotive advertising, and it's claiming an 18-20 percent improvement in fuel economy from its new plastic wrap. As much as we'd love that to be true, it sounds a bit overly optimistic to us. Any eco improvements would definitely depend on many factors, especially the speed at which the vehicle is being driven, but we'd like nothing more than to find that such a simple trick could boost efficiency by such large percentages.
[Source: FastSkinz via MaxGladwell]
Reader Comments (Page 1 of 1)
gorr 8:12PM (2/16/2009)
This can save 0.2% gasoline consumption approx. Maybe of a big airplane like a 747 it can save 10-18%.
What they can do better is building a variable grill opening in the front of the car and let enter just the necessary air for cooling the internal combustion engine for 3-6% approx fuel saving
at low speed and 6-10% at high speed, 100 mph or more.
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jharlan 9:03PM (2/16/2009)
I agree with gorr. 18-20% increase in fuel efficiency? They're dreaming! If you believe that, you would believe you could put an electric motor in a car to turn a generator to power the electric motor and have a perpetual motion machine!
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Herm 10:13PM (2/16/2009)
20% is possible but I think only at hwy speeds, and not 55mph but 70mph and higher. After all it works with golf balls, giving them much longer range. How would you keep all those dimples clean?
Golf balls have a lot more proportional drag due to their small size (Reynolds number) than a much larger car or airplane.. such dimples may just not work on cars or airplanes. Dimples in golf balls has been used for 100 years, by now you would think it would have been applied to airplanes.
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Gordio 10:41PM (2/16/2009)
I think there are dimples on planes actually. when researching why golf balls have dimples, one example they showed were planes.
http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml
Scroll near the bottom.
I think this is also why the tesla has a fake "grill" on the top of the front hood
Gordio 10:43PM (2/16/2009)
Ah! I misread. Those things on jets are not dimples (the article actually says dimples don't work on other objects). Other objects like wings use *alternatives* to dimples that are more appropriate for non-sphereical shapes
GenWaylaid 10:49PM (2/16/2009)
This reminds me of Homer Simpson putting "speed holes" in his car with a pickaxe.
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Eric 11:38PM (2/16/2009)
So vortex generators on wings are to help lift, not to reduce drag. It works in a golf ball because the Reynolds number is low (ratio of the viscous to inertial forces) due to the small size and relatively low speed. Without dimples, the flow separates on the golf ball before it transitions to turbulence and thus makes a big wake. With dimples, it transitions before it separates, making a smaller wake. The added skin friction from the turbulent flow is smaller than the decrease in pressure drag from the wake.
Now with a car or a plane, the Reynolds numbers are much higher, and it's unlikely that there's much laminar flow at all. Cars don't have laminar boundary layers separating.
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Dave 3:04AM (2/17/2009)
"Cars don't have laminar boundary layers separating."
They do, the most visible ones are at trailing body edges.
Dimpling the whole car as already suggested just increases drag on the car with minimal reduction in wake.
All you need to do is to disturb the boundary area near the trailing edges of the car. Vortex generators (as seen on Gordio's link above on the jet) are a more effective way of doing this on a vehicle.
People have already sell vortex generating kits for cars - fuel efficiency gains are usually range from not noticeable to slight improvement. Results could probably be improved with wind tunnel testing on a car by car basis.
There is one rather well known example of vortex generators on a production car, have a look at a recent model Mitsubishi EVO (not the most recent one). However, the primary reason for the VGs on this car was to help direct air towards the large rear wing to reduce lift - not to reduce drag. There is a white-paper detailing how engineers finalized the design of the VGs on the EVO that can be found with a bit of Googling.
MisterK 3:09AM (2/17/2009)
Yay science!
Seriously though, the amount of times I've seen products add dimples "because golf balls have them" is terrifying. those stupid PC case fans come to mind
jim 9:37AM (2/17/2009)
Glad I read the comments before heading out to the garage with a ball peen hammer.
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DJ 9:55AM (2/17/2009)
Could be a gimmick, but it may depend on the particular object being applied to as well. E.g. Zipp is famous for and apparently proven that its dimpled carbon wheels are more aero than their non-dimpled counterparts. Rocket Science Sports has applied the technology to water bottles. Louis Garneau to its aero helmets.
No matter what improvement there is, if there's an improvement, then do. Every little but counts.
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Matt 10:30AM (2/17/2009)
My $.02 is that I think I trust the hundreds of engineers at the multi-billion dollar car companies to determine what makes my car its best... doubt my bubble wrap or whatever will make fuel economy significantly better without making it look significantly worse. If an automaker can get it to work, great, I want it. If not, I'm not experimenting with MY car.
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Ian 11:57AM (2/17/2009)
Another data point:
The Corbin Sparrow (now Meyers Motors NmG) single occupant electric three-wheeler also had (large, 2" diam) dimples on its lower rear and the trailing surfaces of its wheel fairings. The designer, Michael Corbin, should know a thing or two about aerodynamic optimization. At one point, he set the world speed record for motorcycles!
On the Sparrow, the rear dimples might have actually been to create downforce without resorting to a draggy spoiler. From a comment on the half-bakery:
The dimples on a golf ball create lift when the ball has a backspin--letting the ball go higher, and therefore farther. Dimples (to some extent--based on the scale of the dimples) break up laminar flow. Laminar flow is the most efficient airflow on a large scale for penetration (though not neccesarily true when generating lift). If you were making a car that flys, then dimples might help. Since most cars are designed to generate a certain amount of downforce (opposite of lift), in order to keep the car on the road, dimples would obviously be a poor idea. Technical explanation: Dimples create vorticies. Vorticies create drag. This is good on the top side of a lifting surface (or on a spinning lifting surface). Many modern aircraft add efficiency by placing vortex generators on top of the leading edge of an airfoil. The bottom surface always stays as smooth as possible to reduce drag and raise air pressure. On a car, you want more air pressure pressing the car down, so the top surface is smooth (notice how auto makers often leave engine, transmission, exhaust, and suspension components exposed under the car to disrupt laminar flow, create drag, and more importantly, downforce).
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Dave 1:12PM (2/17/2009)
The reason they put vortex generators on the top of airplane wings is to decrease the stall speed.
When the wing's angle of attack gets too high (think angled up), the wind flowing over the top of the wings wants to separate off the lower portions of the wing.
Vortex generators placed in the correct spot create a bit of turbulence which keeps the air flowing along the wing surface (kind of like tripping it) at the expense of adding drag when the plane isn't close to stalling.