Homemade Dimples

vio765

i think it would be a cool idea for bike makers to start making dimpled frames. not just frames, but "dimpling" anything that can be dimpled. if companies wont do it because there is no real benefit, then fine. but if there is, i thought of a way to beat them to the punch. get some good tape that comes in strips and a has a backing, two hole punches (one small, the other bigger) and time. punch the holes in the tape while alternating the different sized punches, cut the strip to the right length and shape, peal the backing off, and BAM! instant technology. so, all you out there tell me why this won't work.

Phill P

http://weightweenies.starbike.com/f...pic.php?t=41330


Note the day the thread was started.....

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garage sale GT

Are you referring to the golf ball effect?

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vio765

yeah pretty much.

garage sale GT

They found Nascar stockers with vinyl roofs were faster than painted steel, so get some of that textured vinyl made for 70's cars! You could finish the edges with a chrome strip.

They used to mess around with the profile of the roof to the extent the rules allowed and would slap vinyl over it to not have to do a lot of filling and smoothing to the bodywork.

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vio765

i have done a little investigating and have a general idea that dimples on wheels are the most efficient use of dimpling technology. I would think this makes sense because the wheels are moving in a circular and straight-line direction. so the wheels are moving through the air much faster than, say, the rider's body. however, Nike started producing its Swift Spin skinsuit and we all know it saved time. remember in the Lance Chronicles when Johan told the scientist in the wind tunnel to keep this skinsuit on the backs of the Discovery Channel? so if dimples CAN help on straight-line objects (read: non-rotating things), why not add them to helmets, frames, shoes, aerobars, forks, etc.? each peice alone might not do much, but when EVERYTHING is dimpled, an increase in speed is more substantial. i found some clear duck tape and some of that "slick" paper that stickers attach to (so i can secure the tape, cut it, then peel off the "slick" backing to apply to the bike). good places might be areas that directly in the path of wind. like the fork, downtube, "wings" of aerobars, front hub, etc. areas where the legs are churning up air might not do anything. places like the seat tube, seat stays, seat post.

garage sale GT

I don't think dimples would help extra on a wheel because of its rotation. The idea is to help the airflow "close up" after a golf ball or bike frame has passed through it instead of cutting a wake. The wheels would cut through the air much the same way if they weren't spinning but you were hovering a millimeter above the pavement while moving at high speed.

Incidentally, tire sidewalls on narrow road tires already seem to be roughened, whether with this end in mind or not.

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dgregory57

Doesn't Zip, or some other wheel have dimples? The wheels with negative drag.

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vio765

Zipp wheels do. you are thinking of the new Sub-9. wicked fast and very expensive. this technology is fantastic. im so happy to be in the time of cycling where technology is making big gains. but at the same time, those TT folks who have money, are buying speed. even if someone has the money to buy the fastest "this or that", i feel it is more for bling when they are NOT at their genetic limits. but if they ARE at their genetic limits, thus not able to produce more power, then buying speed is the logical place to go.

Cervelo emailed me stating that dimpled bike parts are not effective on their bikes. even though i have little professional scientific training or experience, i dont fully accept their statement. these folks are clever. there IS a way and it is only a matter of time before we all are drooling over the latest dimpled forks, frames, aerobars, etc. dimples, in the next few years, will be what ceramic bearings are today; exotic bike gear we would love to have.

ScienceIsCool

Simply adding dimples to something does not automatically make it better aerodynamically. Otherwise, every airline in the world would dimple their airframes to save hundreds of millions of dollars on fuel.

Aerodynamics is incredibly complex (and dynamic! it's right there in the name... ) and there are a very few conditions in which dimples can have a positive effect. I'd trust Cervelo's evaluation on this one.

Most of the 'improvements' these days are of the diminishing returns variety. For example, a stiffer frame and ceramic bearings make such an incredibly small difference that I doubt it could be reliably measured. Defnitely not noticed. Same with the differences in moment of inertia between wheelsets. There are some advantages with aerodynamically superior wheels, but I doubt they are decisive except in time trials.

Money might buy you speed, but it won't buy you very much. Things like body position, clothing fit, and how often you look down are likely to have a much, much larger effect.

In fact, I've been tempted to do a statistical study. To look at as many photo finishes as I can find. And then compare the winner (zipped or unzipped jersey, wheel type, etc, etc) to the other riders in the frame. It should be possible, for example, to say that riders with zipped jerseys are 12% more likely to win a sprint. Or that wheel type has no effect. That kind of thing.

John Swanson
www.bikephysics.com

vio765

[QUOTE=ScienceIsCool]Simply adding dimples to something does not automatically make it better aerodynamically. Otherwise, every airline in the world would dimple their airframes to save hundreds of millions of dollars on fuel.

Aerodynamics is incredibly complex (and dynamic! it's right there in the name... ) and there are a very few conditions in which dimples can have a positive effect. I'd trust Cervelo's evaluation on this one.

Most of the 'improvements' these days are of the diminishing returns variety. For example, a stiffer frame and ceramic bearings make such an incredibly small difference that I doubt it could be reliably measured. Defnitely not noticed. Same with the differences in moment of inertia between wheelsets. There are some advantages with aerodynamically superior wheels, but I doubt they are decisive except in time trials.

Money might buy you speed, but it won't buy you very much. Things like body position, clothing fit, and how often you look down are likely to have a much, much larger effect.

In fact, I've been tempted to do a statistical study. To look at as many photo finishes as I can find. And then compare the winner (zipped or unzipped jersey, wheel type, etc, etc) to the other riders in the frame. It should be possible, for example, to say that riders with zipped jerseys are 12% more likely to win a sprint. Or that wheel type has no effect. That kind of thing.

John Swanson
www.bikephysics.com[/QUOTE

i am referring to only TT bikes when it comes to adding dimpled tape. i dont see dimples on road bikes as being beneficial (pack riding, different riding postion, etc). i totally aggree that dimples, ceramic bearings, and other high-tech goodies only yield marginal results. but the aggregate might yeild something. Zipp's Zedtech front hub saves 2 watts. that isnt much unless a TT rider is up against competition that is of similar capabilities and only a few seconds decides 1st and 2nd place. i have seen it before at my local TTs.
going back to the hubs. add on dimpled tires, skinsuit (when available), helmet (if dimples work there), and frames/forks. total savings could be several watts. but it only works IF dimples provide any advantage. I bet anything that frame makers and other companies are or will experimenting heavily in this idea. so right now, Cevelo is right; no benefit. come 2010 and beyond, those folks will figure it out and mark my words, we will be seeing it soon. at the very least, dimples will act as a placebo and we will go faster because of that! HA!

ScienceIsCool

That's only if you believe Zipps dimpled hubs save 2 Watts at 50 km/hr. Personally, I call BS. Though in the absence of good and reliable measurements, I applaud your efforts to investigate this. Science! Yay! Just be prepared for data that doen't fit your hypothesis.

John Swanson
www.bikephysics.com

vio765

i forget to say that i am thinking about setting up a video camara and TV in front of my bike such that i can fine tune my position on the fly. doing this "visual method" isnt exactly scientific, but since i dont have access to a wind tunnel or trained staff, this will do fine.

TheDarkLord

The link posted by Phill P was meant as an April fool's joke. I'm surprised that you are really taking this seriously. I'm totally with John in this one.