golf ball dimples

[rmaurerjr]

I have a question that we just thought of.

My son and I were watching the TV show "Myth-busters" and they did a test on how the dimples on a golf ball cause a ball to go farther. In their test, the took a car and covered it in 2 inches thick of clay all over the body and tested the gas mileage. After that they put golf ball dimples all over the car and tested again. They increased the the gas mileage from 13 mph to 17 mph (I can't remember the actual numbers but it was substantial)

My son thought we can cover the car in dimples and make it faster by .10 to .001 of a second. That can win races.

Has anyone tried that? I can't test that 100% since our pack track does not have a timer and I think a timer will show the small change.

[zeezop]

My 2 cents:
If your son wants to try it then do so.

Comments:
Mythbusters, probably my favorite show. In the episode they did not start measuring the gain until the car reached the targeted speed so maybe you will not slow down as much on the straight section.

The aerodynamics are probably one of the least important factors; real gains occur when you spend time on alignment, axle and wheel prep.

Looking back at some old cars I saved one of the fastest ones is a slice of cheese drilled with holes that resemble dimples...but the fastest ones are those with the best alignment, axle and wheel prep.

A dimple car would look cool; go for it as it could not hurt and let us know how you made out.

[the woodbutcher]

Now that is what I'm talkin' about. This is what makes this sport so much fun! Engineering and buiding the cars together. Getting the brain engaged and digging, scratching, and maybe even clawing for every last bit of energy these cars have.

I think you should do it. Except, use a steel rod of some sort with a rounded end and tap it with a hammer to make your dimples ...

[zeezop]

I would not want to hammer the car to make the dimples. If possible grind a bit to drill the dimples, might be some router bits or dremel bits that would do the job.

[Talk-n-Derby]

I watched that episode on youtube last nite and the dimple information where it relates to speed, did not actually have to do with speed. The dimples were used to create lift and loft in the ball, they found when they used a dimpless ball it had more intial speed off the tee but could not maintain loft to maintain speed. The dimples kept the ball in the air, therefore "giving the ball speed" because it wasn't hitting the ground where solid friction would slow it down. If dimples worked for speed, drag cars, nascar cars would have dimpled bodies.
Also the dimples if not put exactly uniform could catch air more in one dimple then another then causing the car to possibly shake or move around the track. There would be stability issues.

[rpcarpe]

So, what were the results? I'd like to hear how this car did. I might try this on a pair of spare blocks.

[ljo]

I was under the impression the dimples changed the surface area of the ball, thus it slices through the air more easily.
It would be neat to try. However, it would be difficult to make uniform dimples. Also the dimple size may play an important role. I would think too large a dimple would hurt performance. I am still not convinced aerodynamics is as important as everyone claims, since the speed is not very significant. I think the wedge cars go faster, merely because there is less wood and more weight where it counts. Just my thought, and I am far from an expert. I am backing this thought, with an experimental car I built for the "dads race" at my kids' derby. I ran a solid block(rightfully called the "Brick") that had been hollowed out and rear weighted and was only a tenth slower than my kids winning wedge.

[rpcarpe]

Also, check out two deep lectures on aerodynamics at www.pinewoodderbyphysics.com the lectures 8 & 9 explain the difference between some basic shapes of cars. There is also a video of a Dad and kid changing the aerodynamics w/ a 3x5 card taped to a car.

[2borggold]

Interesting idea! Let us know what you find out.

[nmanhipot]

A well known bicycle wheel manufacturer has been using dimpled rims for quite a while. These guys are wind tunnel junkies and aren't afraid to start over from scratch and take a lot of risks to make professional/competitive level bicycle wheels go faster (2-3k per set, mind you.) Their aerodynamics are optimized for a target speed 30 mph. Of course, the Mythbusters were measuring at 65 mph, but the results were a 14% improvement in mpg (26>29.65).

I don't know how much of a difference it would make at 8 mph, but it's worth a few tests. I considered this myself but I found too much left to do on other fronts.

I believe the theory is that dimples create turbulence which leads to an increase of aerodynamic friction (on the leading edge) but a more significant decrease in pressure drag (on the trailing edge), Pressure drag is a type of separation resistance that keeps the object from moving forward - think of this as the vacuum caused by displacement. The dimples allows for less pressure drag on the back end than laminar flow over a smooth (sphere) effectively reducing the displacement so less energy is lost.

dsc.discovery.com/videos/mythbusters-dimpled-car-minimyth.html