Why are Zipps dimpled?
#1
Port
Thread Starter
Join Date: Jan 2008
Location: Boston
Posts: 6,654
Bikes: 2022 Soma Fog Cutter, 2021 Calfee Draqonfly 44, 1984 Peter Mooney, 2017 Soma Stanyan, 1990 Fuji Ace, 1990 Bridgestone RB-1, 1995 Independent Fabrications Track, 2003 Calfee Dragonfly Pro
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 985 Post(s)
Liked 1,866 Times
in
1,064 Posts
Why are Zipps dimpled?
Why are Zipp rims and hubs dimpled? I get the golf ball reasoning, but if that is so, then why are no other aero products dimpled? Airplanes, cars, cars etc all face greater aerodynamic loads than a bicycle wheel, and yet none are dimpled.
But then the Mythbusters worked on this a while back:
https://www.autoblog.com/2009/10/22/m...-dimpling-mpg/
But then the Mythbusters worked on this a while back:
https://www.autoblog.com/2009/10/22/m...-dimpling-mpg/
#2
Resident Badass
Join Date: Jun 2010
Location: Rochester, NY
Posts: 80
Bikes: 2009 Raleigh Supercourse
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Because it would be a hell of a lot more expensive/time consuming than it already is to dimple every car/airplane/etc that is made. Plus, a dimpled car would look ugly as balls, as shown by the Mythbusters.
#3
30 YR Wrench
Join Date: Aug 2005
Location: Oxford, OH
Posts: 2,006
Bikes: Waterford R-33, Madone 6.5, Trek 520
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 3 Times
in
2 Posts
Marketing. The rider is the biggest aerodynamic impediment. I LOL when I see some totally "aero'ed out" dude with a loose, fluttering jersey. Of course, if you are a PRO, everything little thing counts, but for the average Joe? Naaaah.
#4
Port
Thread Starter
Join Date: Jan 2008
Location: Boston
Posts: 6,654
Bikes: 2022 Soma Fog Cutter, 2021 Calfee Draqonfly 44, 1984 Peter Mooney, 2017 Soma Stanyan, 1990 Fuji Ace, 1990 Bridgestone RB-1, 1995 Independent Fabrications Track, 2003 Calfee Dragonfly Pro
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 985 Post(s)
Liked 1,866 Times
in
1,064 Posts
OK, but then why not things where money is no concern, like fighter planes? And why is Zipp the only company dimpling their cycling gear?
#5
Certifiable Bike "Expert"
Join Date: May 2005
Posts: 5,647
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Actually, money is a concern even for fighter planes.
And if dimples made commercial planes use less fuel, they would pay for themselves very quickly.
I think the real answer has to do with wind velocity and profile, like the dimples only work in some transitional Reynolds number area. But I don't really know much about aero stuff.
And if dimples made commercial planes use less fuel, they would pay for themselves very quickly.
I think the real answer has to do with wind velocity and profile, like the dimples only work in some transitional Reynolds number area. But I don't really know much about aero stuff.
#6
Formerly known as: cpk0
Join Date: Nov 2004
Posts: 300
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I have to facts to support this, but: money is always a concern, even when it's US defense budget money. Dimpling adds huge amounts of surface area, so maybe all that extra material, when it's some exotic composite with super low tolerances for error actually is a limiting factor. Maybe it's not money and LM has done tests and found dimpled material expands differently at mach 1 than flat material. Maybe it has a worse radar signature. Really not sure, but I'm wiling to bet if the golf industry has figured it out, the airforce has at least looked into it. As far as other cycling products, they either don't believe it's worth the R&D costs (wrongly or rightly, I don't know), they just haven't thought about it, or they think putting they efforts into something else (lighter material, better bearings, etc) is a better return on investment. There's no cycling product design newsletter that all of a sudden gives every company the lowdown on each development; sometimes it just takes time for everyone to catch up.
#7
Chases Dogs for Sport
Golf balls are traveling much faster than bicycles and the forward-spinning side is traveling very fast, thus making vortex generation possible and productive. The rearward-spinning side (lower velocity, but still faster than a bike) sees much less benefit, the interaction thus producing lift. A perfectly smooth golf ball doesn't travel nearly as far -- and neither does a golf ball without spin. (That's why a "knuckle-ball" doesn't fly as far.)
Zipp isn't the ONLY company dimpling their cycling gear. A frame manufacturer or two has dimpled the surface of their frames. But, ultimately, the dimples don't make a measurable performance difference at cycling speeds on such an insignificant part of the total surface area of the bike. At cycling speeds, they are better revenue generators than vortex generators.
Last edited by FlashBazbo; 07-09-10 at 08:42 AM.
#8
Senior Member
Join Date: Feb 2010
Posts: 719
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 28 Post(s)
Liked 0 Times
in
0 Posts
I think I read an article where airliners will be dimpled some day.
Fighter jets on the other hand, have to deal with upwards of nine G's, and have to be repairable in the battlefield. Fuel economy and max speed aren't the biggest issues facing a fighter jet.
Dimples are also bad for stealth...
Fighter jets on the other hand, have to deal with upwards of nine G's, and have to be repairable in the battlefield. Fuel economy and max speed aren't the biggest issues facing a fighter jet.
Dimples are also bad for stealth...
#9
Chases Dogs for Sport
And, to incorporate another favorite BF debate: Hairly legs really should offer lower drag than shaven legs. The hair disturbs the boundary layer of air -- same concept as a dimpled surface.
#10
Certifiable Bike "Expert"
Join Date: May 2005
Posts: 5,647
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
You can google "airliners dimpled"... here's a good thread: https://www.airliners.net/aviation-fo...ad.main/51641/
#11
Senior Member
Join Date: Oct 2009
Location: SoCal
Posts: 495
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
they can't dimple commercial planes like golf balls, if they do, then 'frequent flier miles' would have to be changed to 'frequent flier yards'
#12
Uber Goober
If dimpling cars was a good idea, then hail-damaged cars would be worth more, right?
__________________
"be careful this rando stuff is addictive and dan's the 'pusher'."
"be careful this rando stuff is addictive and dan's the 'pusher'."
#13
Banned.
Join Date: Sep 2007
Location: Carlsbad, CA
Posts: 6,434
Bikes: '09 Felt F55, '84 Masi Cran Criterium, (2)'86 Schwinn Pelotons, '86 Look Equippe Hinault, '09 Globe Live 3 (dogtaxi), '94 Greg Lemond, '99 GT Pulse Kinesis
Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 389 Post(s)
Liked 270 Times
in
153 Posts
Does no one remember Ullrich's dimpled TT helmet?
#14
Senior Member
Join Date: Oct 2004
Location: Huntington Beach, CA
Posts: 7,085
Bikes: Cervelo Prodigy
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 478 Post(s)
Likes: 0
Liked 87 Times
in
67 Posts
Why are Zipp rims and hubs dimpled? I get the golf ball reasoning, but if that is so, then why are no other aero products dimpled? Airplanes, cars, cars etc all face greater aerodynamic loads than a bicycle wheel, and yet none are dimpled.
But then the Mythbusters worked on this a while back:
https://www.autoblog.com/2009/10/22/m...-dimpling-mpg/
But then the Mythbusters worked on this a while back:
https://www.autoblog.com/2009/10/22/m...-dimpling-mpg/
#15
Draught
Join Date: Jul 2005
Location: Georgia
Posts: 4,051
Bikes: N-1 where N = number needed
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Seeing as the skin on aircraft can be a stressed member of the airframe, I don't think you would want to dimple it. Think of a dimpled coke can. Not very good at bearing stress.
#16
ɹǝʇsɯıʇ
Join Date: Jun 2006
Location: MD
Posts: 840
Bikes: 2011 Focus Whistler // 2011 Cannondale CAAD10 // 2009 Scattante XRL TT // 1993 Cannondale R400
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
#17
Senior Member
Definitely.
#18
Banned.
Join Date: Sep 2007
Location: Carlsbad, CA
Posts: 6,434
Bikes: '09 Felt F55, '84 Masi Cran Criterium, (2)'86 Schwinn Pelotons, '86 Look Equippe Hinault, '09 Globe Live 3 (dogtaxi), '94 Greg Lemond, '99 GT Pulse Kinesis
Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 389 Post(s)
Liked 270 Times
in
153 Posts
#19
Le Crocodile
Join Date: Oct 2005
Location: Santa Barbara Calif.
Posts: 1,873
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 370 Post(s)
Liked 787 Times
in
311 Posts
Here is a little cost/fuel economy aviation related story to think about........
My brother-in-law is an exec. for a big aircraft firm, he once told me about these new fasteners for the upholstery/trim in the large jets that weighed less than the current ones. These took big bucks to develop.
I asked what the weight savings were. He said it was roughly 54 pounds..........not per seat etc., but for the entire aircraft. Yes, the huge aircraft would weigh only 54 pounds less! That just illustrates the importance of efficiency in the aircraft business.
If the average Joe knew just how expensive it is to run these beasts, they wouldn't bring so much darn luggage and quit *****ing about ticket prices.
Back to the dimples.........
My brother-in-law is an exec. for a big aircraft firm, he once told me about these new fasteners for the upholstery/trim in the large jets that weighed less than the current ones. These took big bucks to develop.
I asked what the weight savings were. He said it was roughly 54 pounds..........not per seat etc., but for the entire aircraft. Yes, the huge aircraft would weigh only 54 pounds less! That just illustrates the importance of efficiency in the aircraft business.
If the average Joe knew just how expensive it is to run these beasts, they wouldn't bring so much darn luggage and quit *****ing about ticket prices.
Back to the dimples.........
#20
Senior Member
Join Date: Aug 2009
Posts: 8,550
Bikes: Wilier Izoard XP (Record);Cinelli Xperience (Force);Specialized Allez (Rival);Bianchi Via Nirone 7 (Centaur); Colnago AC-R Disc;Colnago V1r Limited Edition;De Rosa King 3 Limited(Force 22);DeRosa Merak(Red):Pinarello Dogma 65.1 Hydro(Di2)
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 551 Post(s)
Liked 277 Times
in
145 Posts
Dimpled jerseys and bib shorts FTW!
#21
he said member
Join Date: Sep 2008
Location: is everything
Posts: 13,802
Bikes: yes please
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 2789 Post(s)
Liked 1,951 Times
in
1,207 Posts
The dimples have something to do with breaking up the boundary layer of air that clings to the surface passing through it. you wouldn't want to do that (except under certain conditions) to an airplanes wing, you loose lift and stall the wing.
#22
ɹǝʇsɯıʇ
Join Date: Jun 2006
Location: MD
Posts: 840
Bikes: 2011 Focus Whistler // 2011 Cannondale CAAD10 // 2009 Scattante XRL TT // 1993 Cannondale R400
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Maybe not to the wings, but to the fuselage?
#23
Version 7.0
Join Date: Oct 2006
Location: SoCal
Posts: 13,127
Bikes: Too Many
Mentioned: 297 Post(s)
Tagged: 0 Thread(s)
Quoted: 1340 Post(s)
Liked 2,482 Times
in
1,457 Posts
I googled dimple tape and stumbled upon this aviation discussion and post 16 seems to answer the question of why and where to use dimples. There are some other posts where pilots tried dimple tape on their props and wings with varying results. https://www.oshkosh365.org/ok365_Disc...5&topicid=2346 So I suspect that like the golf ball the bicycle wheel is a less than ideal airfoil and as such the rim benefits from dimpling.
I can't even spell enigener but from what I have read, dimple tape and vortex generators do the same thing, They increase the turbulent boundary layer which can fill in areas of a less than ideal airfoil. G.A. AIRFOILS ,Harry Riblett. In his book he shows the benefit - need of VGs on less than ideal airfoils and how to improve airfoils. Assuming you can change your airfoil.
The golf ball is less then an ideal airfoil and needs the dimples. A well designed airfoil for a specific purpose should not need them.
Any disturbance to the boundary layer increases drag, but if this disturbance is approximately 20% or greater from the leading edge the amount of drag is significantly reduced. THEORY OF WING SECTIONS, Abbott and Doenhoff.
Maybe if your wing - prop airfoil is somewhere between a golf ball and a well designed section they should be an advantage.
As for wing tips, drooped or upright they should not be needed if the wing platform was well design for a specific purpose. I got this from a seminar by "Raymer" at Oshkosh this year. He also has a book on design.
So if you had a good airfoil for the purpose no "improvements" should be needed. Not much help huh.
As for Marvel Mystery Oil on the farm we found trans fluid did about the same thing.
I can't even spell enigener but from what I have read, dimple tape and vortex generators do the same thing, They increase the turbulent boundary layer which can fill in areas of a less than ideal airfoil. G.A. AIRFOILS ,Harry Riblett. In his book he shows the benefit - need of VGs on less than ideal airfoils and how to improve airfoils. Assuming you can change your airfoil.
The golf ball is less then an ideal airfoil and needs the dimples. A well designed airfoil for a specific purpose should not need them.
Any disturbance to the boundary layer increases drag, but if this disturbance is approximately 20% or greater from the leading edge the amount of drag is significantly reduced. THEORY OF WING SECTIONS, Abbott and Doenhoff.
Maybe if your wing - prop airfoil is somewhere between a golf ball and a well designed section they should be an advantage.
As for wing tips, drooped or upright they should not be needed if the wing platform was well design for a specific purpose. I got this from a seminar by "Raymer" at Oshkosh this year. He also has a book on design.
So if you had a good airfoil for the purpose no "improvements" should be needed. Not much help huh.
As for Marvel Mystery Oil on the farm we found trans fluid did about the same thing.
#24
he said member
Join Date: Sep 2008
Location: is everything
Posts: 13,802
Bikes: yes please
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 2789 Post(s)
Liked 1,951 Times
in
1,207 Posts
But then to what effect. the fuse is already fairly aero, would the extra cost of manufacturing, engineering, etc ever be recouped by the slight improvement in efficiency? And some fuselages are a lifting surface to, while not completely they do contribute.
#25
Version 7.0
Join Date: Oct 2006
Location: SoCal
Posts: 13,127
Bikes: Too Many
Mentioned: 297 Post(s)
Tagged: 0 Thread(s)
Quoted: 1340 Post(s)
Liked 2,482 Times
in
1,457 Posts
Further to my other post...I have a Zipp Sub9 dimpled disc. However, HED has a very nice web app that compares the aero efficiency of wheels as a function of yaw angle. https://www.hedcycling.com/aerodynamics_technology/ If you click on the sub9 button, you will see that the wheel performs best when the wind is at an angle. Hence, the surface of the disc is not a great airfoil at all wind directions. I suspect Zipp played around in the wind tunnel to come up with the best design and dimples improved aero performance over a greater range of yaw angles.