And honestly, who among us wouldn’t love to be able to proudly proclaim our dimpled bottoms?
Did it matter whether the body had concrete shoes on?
I think most obvious reason why cars dont have this is ugliness 
Not as long as they had already turned in the absentee ballot for it.
The diffuser system on a racecar works by taking the fast incoming air at high pressure at the front of the car and directing the flow into a progressively higher-volume “chamber”. As the air expands and exits the rear of the car, it acts as a pump to create an area of lower pressure under the car, creating downforce.
Again, there is no area on the bottom of the car where jacket separation is a problem, it’s more or less a flat plane until the diffuser. Adding dimples would increase skin drag without giving the corresponding benefit of reducing a turbulent wake.
Dimples only really work on blunt, non streamlined shapes, because only in those shapes is the amount of drag caused by separation larger than the amount of skin drag. For a boxy passenger car, there might be some benefit, but for a race car (or plane or whatever), they would harm more than help.
I think the real reason, and the simplest of all, is that no one really cared about MPG until as of late. If people --especially in the US-- actually card about MPG you would not see Hummers, Suburbans, etc. driving around. They probably would not have become as popular as they did.
So, now, that people are way more MPG aware then a feature like this would probably take off especially if proven to work.
But, the real question is, will the cost of the design and implementation of this feature, that will be passed on to the consumer, be worth it for the consumer for the life of the car? We’re talking 26 to 29 MPG here… let’s assume 10 gallon tank here, we go from 260 MPG to 290 MPG… WHOO HOOO! A gallon of gas down the road from me is $2.60 @ 87 octane. So, assuming 200,000 miles out of the car, I see about 800 gallons in difference. Which at $2.60 is roughly $2000. So, the design and implementation cost that is to be passed on to me would have to be substantially lower for me to even consider it. And, they know this which is why it probably has not been done.
eb
Another possible reason manufactures don’t do it is possibly the MB didn’t have accurate results. When vehicle manufactures do fuel economy tests it is incredibly expensive and time consuming to get accurate results. You need control vehicles to account for ambient conditions lots of driving over varying conditions etc. I’ve found that simply the weather or temperature changes between their tests could easily make a 10% change. Try driving the same route with your car twice and watch the mpg display. One day it will be 20 and then the next it will be 18. Where did that 10 % change come from.
I don’t get this-the late Howard Hughes found that building an airplane (specifically the H-1) with flush rivets gained hime an extra 25 MPH speed. If dimples reduced drag, then aircraf with exposed rivet heads should have flown faster.
Golf balls don’t travel in space in the same way that cars do, so you can’t take one technological advantage from the golf ball and expect it to work in the car.
If cars traveled by flying through the air in a constant state of rotation with no control other than the initial force of propulsion, then maybe cars with dimples would work well. And it would also help if they were spheres.
The dimples in a golf ball induce spin which helps with either distance (because of an increased rate of climb) or control, or both. Dimples don’t increase aerodynamic efficiency.
The main issue in body panels is stiffness. You can increase stiffness, or resistance to bending by choosing a material of greater structural strength or increasing the thickness of the panel. Theoretically,when you double the thickness of a panel, you increase the stiffness by a factor of eight.
Think corrugation of a culvert pipe. By increasing the panel cross-section thickness you get a much greater resistance to crushing the pipe. In effect, you’ve increased the thicness of the panel. The corrugations are strategically placed however to resist the lateral loads on the pipe.
Dimpling can have the same effect. Or not. If the dimples are adjacent and staggered I can see a significant increase on strength to easily overcome the thinning of the metal. On the other hand, if the dimples are placed further apart or arranged in parallel rows. I would definitely agree with you.
Are you making this up as you go?
The club imparts spin; dimples do not.
I recommend you pick up a fluid mechanics textbook and read about the interaction between form drag, skin drag, and boundary layer separation on bluff bodies.
Uh, that’s not what their expert said.
OK, I misspoke about the dimples inducing spin.
http://www.freshpatents.com/-dt20091001ptan20090247325.php
(This is public domain information, so no copyright infringement concerns)
"The spin rates of golf balls affect the overall control of the balls in accordance to the skill level of the players. Low spin rates provide improved distance, but make golf balls difficult to stop on shorter shots, such as approach shots to greens. High spin rates allow more skilled players to maximize control of the golf ball, but adversely affect driving distance. To strike a balance between the spin rates and the playing characteristics of golf balls, additional layers, such as intermediate layers, outer core layers and inner cover layers are added to the solid core golf balls to improve the playing characteristics of the ball.
By altering ball construction and composition, manufacturers can vary a wide range of playing characteristics, such as resilience, durability, spin, and “feel,” each of which can be optimized for various playing abilities. One golf ball component, in particular, that many manufacturers are continually looking to improve is the center or core. The core is the “engine” that influences the golf ball to go longer when hit by a club head. Generally, golf ball cores and/or centers are constructed with a polybutadiene-based polymer composition. Compositions of this type are constantly being altered in an effort to provide a targeted or desired coefficient of restitution (“CoR”), while at the same time resulting in a lower compression which, in turn, can lower the golf ball spin rate and/or provide better “feel.”
The dimples on a golf ball are used to adjust the aerodynamic characteristics of a golf ball and, therefore, the majority of golf ball manufacturers research dimple patterns, shape, volume, and cross-section in order to improve overall flight distance of a golf ball. Determining specific dimple arrangements and dimple shapes that result in an aerodynamic advantage involves the direct measurement of aerodynamic characteristics. These aerodynamic characteristics define the forces acting upon the golf ball throughout flight.
Aerodynamic forces acting on a golf ball are typically resolved into orthogonal components of lift and drag. Lift is defined as the aerodynamic force component acting perpendicular to the flight path. It results from a difference in pressure that is created by a distortion in the air flow that results from the back spin of the ball. A boundary layer forms at the stagnation point of the ball, B, then grows and separates at points S1 and S2, as shown in FIG. 1. Due to the ball backspin, the top of the ball moves in the direction of the airflow, which retards the separation of the boundary layer. In contrast, the bottom of the ball moves against the direction of airflow, thus advancing the separation of the boundary layer at the bottom of the ball. Therefore, the position of separation of the boundary layer at the top of the ball, S1, is further back than the position of separation of the boundary layer at the bottom of the ball, S2. This asymmetrical separation creates an arch in the flow pattern, requiring the air over the top of the ball to move faster and, thus, have lower pressure than the air underneath the ball.
Drag is defined as the aerodynamic force component acting parallel to the ball's flight direction. As the ball travels through the air, the air surrounding the ball has different velocities and, accordingly, different pressures. The air exerts maximum pressure at the stagnation point, B, on the front of the ball, as shown in FIG. 1. The air then flows over the sides of the ball and has increased velocity and reduced pressure. The air separates from the surface of the ball at points S1 and S2, leaving a large turbulent flow area with low pressure, i.e., the wake. The difference between the high pressure in front of the ball and the low pressure behind the ball reduces the ball speed and acts as the primary source of drag for a golf ball.
Advances in golf ball compositions and dimple designs have caused some high performance golf balls to exceed the maximum distance allowed by the United States Golf Association (USGA), when hit by a professional golfer. The maximum distance allowed by the USGA is 317 yards±3 yards, when impacted by a standard driver at 176 feet per second and at a calibrated swing condition of 10°, 2520 RPM, and 175 MPH with a calibrated ball. According to the USGA, there are at least five factors that contribute to this increase in distance, including: clubhead composition and design, increased athleticism of elite players, balls with low spin rates and enhanced aerodynamics, optimization in matching balls, shafts, and clubheads to a golfer's individual swing characteristics, and improved golf course agronomy. Even though numerous factors influence the increase in distance, golf traditionalists have been demanding that the USGA roll back the distance standard for golf balls to preserve the game. The USGA has recently instituted a research project to design and make a prototype golf ball that would reduce the maximum ball distance by 15 or 25 yards. (See “USGA letter to manufactures takes ball debate to new level,” by D. Seanor, Golfweek, pp. 4, 26, Apr. 23, 2005)."
I didn’t see the mythbusters episode but I still don’t see how they hope to simulate the effects of the golf ball surface on a non-spinning car surface.
My question is this; did they really need to put dimples over the whole body of the car? Dimples would seem to only be necessary past or around a certain transition point… that is the point where the rear of the car starts to taper back down and the vacuum would otherwise be more strongly formed.
On a golf ball it is not possible to know which side will face forward so the whole surface would have to be dimpled. Perhaps the ball would eventually put the higher drag surface to the rear but there is no telling how it would behave until that happened.
If it is not necessary to cover the entire surface then you might be able to have your cake and eat it too with an aerodynamic shape and better transition that allows you to keep some of the classic lines of a car while improving fuel efficiency.
If you do it right, ALL science is “fun science like entertainment”
If you do it wrong, Its impossible to teach.