no science involved but Dee Wescott makes Glass louvered deck lids solely on the request of some Bonneville racers claiming that they were good for 10 mph at top end. He thought it was funny, I miss him
Dimpling- its the new flatblack! A serious note on flat paint- they may be on to something with the surface tension vs. drag theroy. I've also wondered why some of our top military jets are painted with flat (albeit I'm sure super special) paint. I don't believe it wouldn be just by chance.
isn't the point to make air flow over air?, i have read that in intake runners leaving them with a ruff surface traps a thin layer of air, and then the intake charge never touches the walls of the runners, less friction and fuel is less likely to form droplets on the walls, someone needs to apply for a goverment grant to study this effect.
Yep, I've heard intake theory as well. Some folks state the same when porting an engine. Some feel making the runners too smooth/slick it is counter-productive. Man, a grant to make even hot rodding green! That would be some lucky sumabitch! Thanks Obama!
Something about "attached" flow. If the flow is laminar, then the layers "shear" one against another. If the flow becomes turbulent...read: a big rise in energy disipating, (or drag), then at certain speed range the dimples help by lessening the expansion of the turbulent zone? The points about scale effects and density of the fluid (air) are helpful.
Being the government probably the only thing that makes it "super special" is that some defense contractor sells it to us for 11 million dollars a gallon.
To expand on Budd's #33 comment... While building the Swamp Rat 33 for Garlits in '88, we had a fellow come down from Omaha who was involved with air flow theories. His work had to do with adding a micro thin layer to all body surfaces of a material that had miniature groves pressed into it. The material would be installed so the grove went from front to rear on the body. The premise was that the groves would fill in and create a barrier layer so the air passing over the body did not actually touch the body. By eliminating the laminar layer of air (the air that actually touches the body and created resistance) the streamliner wold achieve greater speed due to the reduction of the resistance of the air it was being pushed through. Do to cost issues, we were never able to test the theory on the salt.
It's been my understanding that the flat coating on stealth fighters and bombers had a lot to do with absorbing radar waves. Kind of sucking it up rather than reflecting it back to the source.
I beleive that is true. I'm thinking more of like the F-16, F-18 & A-10 (and the like) that have flat paint on it. Maybe it's more to do with camo than speed. I would just think that it is doing a little of both.
Yea but when you put mentos in diet coke you can put the lid on real fast and slam it on the ground and it will take off like a rocket, I mean really who can really drink diet coke its like pond water .
geez.. whats next red wheels on stealth bombers?? Whats funny is just like you guys the first thing I thought when I watched the episode is if anyone has tried that at bonneville.
ever seen the vehicle wraps they use in like nascar for lettering? they cover the whole car with decals. there's a company out there doing this golf ball type dimples built in to their vehicle wraps. should be an easy test on the flats, one run as a base and the next with the wrap to see a change http://www.fastskinz.com/
Look up the Corbin Sparrow... I used to live in the town where they built em. I toured the factory and remember asking why they had dimples on the rear panels.... the answer was golf balls
That is RAM material, Radar Absorbant Material. It comes in various forms that I've seen like paint, coatings and sheet material. At work we had one part for a plane that had a RAM coating on it, supplied by Rockwell. Totally proprietory, we had no idea what it was. We also had some sheets of RAM stock that was about 12" x 12" and an 1/8" thick. I wanted to spirit some away to lay inside the doors and hood of my old Mustang, it was sitting around on a shelf. No idea where it went to or who wound up with it. This was at an immense defense contractor facility and things got lost all the time. As for paint, it's not a Sherwin Williams item or available at Lowes. Bob
boats are the same way, even though they're slower. A super shiny bottom is slower than a bottom that is wet sanded. Somehow their is more friction on the shiny surface, and the water rolls down the wet sanded surface. There was also some crazy grooved surface that was supposedly faster than a flat/smooth surface, somehow it was like mini-aerodynamics forcing the flow around the hull. TP
I know this for a fact. I used to paint race ski's (jet ski's)........ I was always told. "dont slick out the botom, just wet sand it with 400 grit". Those race guys swore by it.
They may move slow, but I move pretty quickly away from those chicks. So maybe it works in opposite...
Unless they ran through air that was scaled up the same ratio as the golf ball..... it's all bullshit.
your right!!!!!!!! good idea, i'm going to try that, could just use a ball stone on the rotary tool, why not huh?
an interesting test would be to have a belly tank with two exact bodies, one with dimples and one without.
There is a company in california that sells vynal wraps that have dimples in them. They market it to people who want to get 2 more mpg out of their econobox. When I heard about it I wanted to start my own company that does the same thing but markets to bonneville guys.
A golf ball is dimpled to convert its boundary layer from laminar to turbulent at a lower speed than it would normally occur. This conversion from a laminar boundary layer to a turbulent one is dependent on a lot of things, and the speed at which it happens is unique to a given shape. Golf balls typically leave the tee around 150 mph, and a smooth ball would usually still be in laminar flow at that speed. Also note that the improvement in the drag coefficient in changing from laminar to turbulent is also shape dependent, and it just happens to be beneficial for a sphere. Every year aircraft manufacturers and race teams spend millions of dollars and thousands of hours in wind tunnels figuring out how to squeeze every last drop of fuel and shave every single tenth off the clock. While I love mythbusters, their "science" can leave a lot to be desired. Having guys drive a car around to figure out fuel efficiency based on aerodynamics involves so many variables its amazing they came out with any kind of relevant data. Simply using the same operator on the same course doesn't guarantee the exact same fuel consumption, a slightly heavier foot could easily account for everything. Not to mention engine operating temperature, tire temperature and pressure, wind conditions, the exact path taken on the track, the ambient air temperature and density, humidity change between tests, etc, etc, etc. The only way to truly get any accurate data on that myth would be to put the car in a wind tunnel and calculate the drag coefficient. Not as much fun, but the only true scientific way to do it. A sphere is a simple, uniform shape. Cars, planes, boats etc all have directionality, complex shapes and curvatures that have a huge effect on boundary layer size at a given spot. Just look at an aircraft- leading edges are very smooth, other areas are relatively smooth (flush rivets and panels etc) while some places don't even bother with flush rivets. Dimples might help in one area and be catastrophic in another (a leading edge of the wing for example). On a car, where the boundary separates (and not just its thickness) will be a large part in determining down force and lift, not just drag. The air flow over a sphere is the same on all sides, so, no lift, no downforce, just drag. I don't think I need to say what happens if your car creates lift somewhere. http://www.youtube.com/watch?v=SHx9MePSBYk&NR=1 Turbulent flow is one of those areas that remains outside of the realm of "pure" math. There is no "pure" turbulent flow equation, turbulent flow is modeled on equations derived from empirical data based on wind tunnel data and use fairly large correction factors. Which is why so much money gets spent on complex computer modeling and why wind tunnels are really the only way to figure out with any certainty how a given design will work in the real world.
well the dynamics on an aircraft are completely different then on a car and used for a different reason, thats the reason they aren't used on airframes. they did a very scientific test to precisely measure how much fuel was used by a car with and without dimples, they covered a car with clay first, then did the test, then they dimpled the clay, to make the measurements accurate, they even took the clay that was removed,put it in a container and put it back in the car, to make sure the weight was exactly the same. they got an 11 percent reduction in fuel mileage. they also did the tank tests to show how the dead air area behind a car differs. I don't see why scaling it up would be that different, auto makers have tested small scales for years in wind tunnels and other ways to get data. it's a proven way to test prototypes. I think the main reason they aren't making a dimpled car, is who wants a car that looks like a dam golf ball?
WARNING OFF TOPIC MIDNIGHT POST... Actually.. Disclaimer: I am not an engineer..but the race bike mech is..so this may be amatuer description at best. The intake runners on my F/I motorcycle showed an increase flow on bench..and about 3% power on dyno..versus smooth bore...at WOT The air vortex is decreased..as the air speed along the bore is slowed. The smooth bore seemed to cause a vortexing..with the air speed quicker(less mass at edge along wall than center of bore)) along the wall. That seemed to cause the flow to curl into the center of the bore disrupting the laminar flow. When we peened the walls the flow became less disturbed..and intake velocity and charge mix was more preserved. The rough walls keep the mix charge along the wall and keep the flow more unified..and less disrupted. We had mated all the ports and runners..and them A/B'd two sets of runners..smooth..polished was worst. Peened lightly consistently stronger. Smoother acceleration..more power. The injectors are 12 micro jets..and the heads are DOHC twin plug waste fire..so perhaps this would be lost with more traditional plumbed intake.. This is a more common practice on road race F/I bikes..a few years ago Duc's and RC51s.. Now back to our regular programming...
So you're all saying I shouldn't flat sand my gloss paint, if I leave the orange peel in it it'll go faster?
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