? about Golf ball dimples
 

I have several large areas I want to cover with a material that will have golf ball dimples on it, (I will be making them, figured out how to do that). My ? is; is SCALE important, for the effect. I'd like to make them 1 1/2" in diameter, and 1/8" deep.Its a lot more labor to make them say, 1/2" in diameter.(Imagine doing a 4'x8' sheet, using a drill to make each dimple. A LOT more work!) So, will I still get the effect of reducing the boundary layer, and therefore the drag on the air flowing over the surface? Anybody Know??Dutch

Perhaps someone more highly degreed than me can answer, but I do know that even on golf balls the dimple size & pattern vary from manufacturer to manufacturer. They all have their own different (but similar) beliefs on the dimple patterns, so I doubt that anyone here will have such a conclusive answer.

-BC

I also have something to add. Would dimples behave the same way? We're talking about totally different shapes. A sphere and a flat plane. Certainly this should have some effect as to their behavior, and maybe influence optimal size, proximity, and arrangement?

-Jay

Ok, no expert here, but looking for Wikipedia (ha! again even less expert there!) anyway:
Most golf balls on sale today have about 250 – 450 dimples.
Golf equipment maker Callaway has introduced a ball with hexagonal dimples to increase the dimpled area on a golf ball, as hexagons tesselate unlike circles.
Super-distance balls have deeper dimples and are heavier than allowed by regulation, which allows them first to maintain momentum and second to maintain a thicker "envelope" of still air around them which reduces turbulence and wind resistance. Marketers of these balls generally advertise a 12-yard gain on most distance shots.


Those are the points of interest as I see it. So clearly amount of dimples can vary, they also talk about some balls with 400 larger diameter holes and 600 pinhead holes, so clearly you can mix size too.
The thought of hexagonal is interesting, I wonder how much it helps/affects.
The 'super distance' ball notes that deeper dimples cause a tighter envelope of air. Not sure if that's true but definately I would want to look in to an anaylsis on depth and how much it helps.

Where are you planning to place these on a car? Since it's about the boundary layer I would think it's main purpose would be to keep air connected even when the shape of the object is dropping off too fast to normally maintain attachment.

That is, if you already had a perfect teardrop, dimpling would not help, and neither would it help a kammback, because it's too severe, but dimpling the back of a VW bug should have some pretty amazing results, becuase it's not smooth enough as a rain drop to maintain flow and will lead to turbulence, but close enough that dimples should keep flow attached further.

I know a lot have talked about it, and I read that Smokey U did it, but I'm doing it! I'm making a duct, 34" wide and 16" high, from the tranny to behind the rear axle. At the front, it gets about 5' wide, also at the back. Complete belly pan, even under the engine bay. Object is to carry the positive pressure air at the front of the truck to the negative pressure air at the back.Going to use this material to line the duct, as well as on the bottom surface of the belly pan.May also use it on the roof, from the top of the windshield to the back, and maybe on the last 3' of the sides.The truck is a Divco milk truck; google Divco club of America to see what it looks like, or imagine a slightly smaller version of the early UPS trucks.Also going to put a visor on it, and cut holes between the bottom of the visor, and the top of the windshield, and duct that to the back as well.All the ducted air will join up at the back, and 'come out' of a large hole above the back bumper, 16"x34", 2 holes about 16' square on each side of that, and 2-3" dia. holes running up the back, at the corner, and across the top.(Of the back).So, thats the plan.If I drive down a dusty dirt road, and have very little dust behind me, I'll know it worked! Jim

I originally wanted to post a joke about "speed holes", but Google Images wouldn't give me the picture I need for it. :) Then I read that you're using it in a belly pan which reminded me of something I've got...

My 2008 Volkswagen has golf ball dimples on some of the factory belly pan parts.

https://lh4.ggpht.com/ronanian/SBm-Ya...0/IMG_0658.jpg

Is this part from a Golf? :rolleyes:

LOL, now that you mention is, "Rabbit" is just US-marketspeak for "Golf". :p

Can't tell from the pic, What is the diameter, and depth, approximately, in inches, please!!That looks like what I'm talking about!!Jim

Vaguely speaking from memory, the diameter was about 1 inch and depth was almost nothing, at most a quarter of an inch. I just reviewed my photos of it and of the car's undercarriage, but they're not very good for determining size. I'll leave myself a note to try to get measurements when I get home from work.