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Full Detail for better MPGS????; Wash and Wax your way to better MPGS.
Topic Started: Aug 18 2009, 04:56 PM (2,137 Views)
Potter
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Col. Potter

Bad Bent
Oct 3 2009, 10:44 AM
"Very interesting...."- Artie.

Great video, greggholmes :rocker

I'm going to relocate my Vortex Generators to see if I get less drag, same principle. I'm also working on the 'dirty is better for mpg' theory having become a lazy :shit recently. :'(

But we can all expect our mpg numbers to decrease... I just saw the first snow flakes of the season. October 3... :banghead
ok ok ive been wayyyy to busy to keep up with this and forgot about it :smackface im gonna detail the car this week, gather info, and keep it up for a month or so. then let the car go to :shit then take records.... ive been so busy i havent had the chance to even keep up with my own personal fuel log.

either way i hope it goes good.
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Murf 59
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Fer' shame P, that is 50 lashes with a wet noodle :lol
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Bad Bent
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Facetious Educated Donkey

Obsessions can have their bounds, eh.

No problem, I forgot about the test also. :lol

As for the golf ball check out this link: Golf Ball Dimples & Drag.
"These results tell us that causing a turbulent boundary layer to form on the front surface significantly reduces the sphere's drag." and
"The reason we do not see dimples on other shapes, like wings, is that these particular forms of boundary layer trips only work well on a blunt body like a sphere or a cylinder." or
"More streamlined shapes like the airfoils used on wings are dominated by a different kind of drag called skin friction drag." Relating to Mr. Mruf's observation.

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Murf 59
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It is the same kind of effect on pickups with the tail gate down. They think it is causing less drag. It is backwards from what you might think. With the gate down the air just passes over the truck and it is a mess. With the gate up, it traps air in the bed forming an air cushion. The air now passing over it see the cushion as a solid. And the air travelling over has a cleaner path way. Sorry I am not explaining this really well. The Mythbusters did a show on this.
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Potter
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Col. Potter

Mr Murf 59
Oct 3 2009, 10:56 PM
It is the same kind of effect on pickups with the tail gate down. They think it is causing less drag. It is backwards from what you might think. With the gate down the air just passes over the truck and it is a mess. With the gate up, it traps air in the bed forming an air cushion. The air now passing over it see the cushion as a solid. And the air travelling over has a cleaner path way. Sorry I am not explaining this really well. The Mythbusters did a show on this.
saw that episode... i think you explained it well.

So that means my MPGs might see a drop when i convert the Nissan into a flat bed.
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Murf 59
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I am not sure about the flat beds. And I do know the CA laws as well as that of NV. In Nv falt beds had the same price insurance as HI end Corvettes. The problem with them as far as the Ins co goes, things fall off them all the time. Driving the price of Ins up. NO win situation.
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greggholmes


Mr Murf 59
Oct 3 2009, 09:20 PM
GH is right. They found that with the dimpels in the golf ball, it will fly farther and staighter.
On the WWll B29 bombers. They did not paint them to save fuel and bomb load. The amount of paint to cover one of those big planes weighs alot.
thats why american airlines doesn't paint there planes. the weight of the paint equals about two more passengers.
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Woodie
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Same reason Mercedes doesn't paint their race cars. The name "Silver Arrows" isn't just a marketing gimmick, the origin was weight reduction.
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john.
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[ *  *  *  *  * ]
I read something somewear about plastic film you can stick on your car that has the dimpled texture of a golf ball.
They claimed a 5 % increase in fuel economy. I think it was popular mech I read.
Had to coat the whole car for the 5%
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Coche Blanco
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john.
Oct 10 2009, 06:38 PM
I read something somewear about plastic film you can stick on your car that has the dimpled texture of a golf ball.
They claimed a 5 % increase in fuel economy. I think it was popular mech I read.
Had to coat the whole car for the 5%
Shark skin; false marketing scheme.

They used to paint the space shuttle's fuel tank, but well it was lighter not to.
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Murf 59
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greggholmes
Oct 5 2009, 05:35 PM
Mr Murf 59
Oct 3 2009, 09:20 PM
GH is right. They found that with the dimpels in the golf ball, it will fly farther and staighter.
On the WWll B29 bombers. They did not paint them to save fuel and bomb load. The amount of paint to cover one of those big planes weighs alot.
thats why american airlines doesn't paint there planes. the weight of the paint equals about two more passengers.
Which if you add up all the weight saved, you can carry more fuel and bombs :rocker
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Murf 59
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I just saw the thing on Mythbusters about the dirty car V clean car milage. They did the whole thing with the dimples on the golf ball to a car. I know they are not very scientific, but they got a 11% increase with the dimples in the clay form they added to the car. I am not describing this well, but it was cool anyhow.
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nerys
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Grr

Hmm aerodynamically this gets "interesting" while the mass of dirt WILL effect your mpg you will never be able to measure it. Just not going to happen. too many micro variables that are larger than the dirt.

NOW the drag you might see measurable effect (just barely)

on drag there are at least 2 kinds drag involved here.

You have what people typically call Frontal Surface Area (dirt will have zero measurable effect on this)

then you have Parasite Drag or "surface drag" as some call it in automotive circles.

this is the drag you will reduce with waxing etc.. while not the bulk of drag IS IT measurable and significant.

now with parasitic drag you have another function called laminar flow. this is the ability of the air stream your shoving asside to be able to "STICK" to the surface of your car's body.

too much deviation and the laminar flow "breaks" and the air stream detaches dramatically increasing parasitic drag.

this is why people install "kambacks" on there cars. the wind can not make that "bend" over your roof onto the hatchback. it breaks free and increases your tail drag by quit a lot.

a good example of this is imagine a 2door metro. Now imagine a modified 2 door metro and SLICE the back of the metro off at the rear roof line so you have a flat square back.

not nearly as aerodynamic right? well THAT aerodynamically is exactly what your 2door metro looks like to the air. it "can't" stick to your car when it hits that point. this is why the kambacks have such a great effect. it dramatically reduces your "base drag" (thats what we call it in rocketry)

think opposite of Frontal Area drag. the closer you can RETURN the air to its previous configuration at its exit point from your car the LOWER your overall drag will be. this is why the Teardrop shape is so clean and so efficient. (think Aptera)

Now interestingly enough super clean surfaces MIGHT NOT be as aero clean as a non smooth surface. slight surface imperfections CAN assist in maintaning laminar flow which more than makes up for the slight increase in surface drag. Think Golf Ball.

this is still new stuff the science is not nailed down yet but its very possible we might strategically make certain areas of our cars NON SMOOTH in order to encourage the maintenance of laminar flow. Thats still in the future a bit.

for now it should be safe to assume that a smoother skin should result in better drag performance.

More important than your actual skin surface would be transitions. think body panel joints. Mold lines Mold extensions (the rubber around the windscreen your doors etc.. your wipers) the more you can smooth out those things the better your laminar flow and parasite drag will be and the cleaner your car will be aero wise.

Hope that helps.
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billy508
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billy508

More info than you need....MAINTENANCE
Beyond the need for washing, the comparative cost of maintaining painted and polished surfaces is significantly affected by the policies of individual operators. Most repaint their airplanes every four years, often during a scheduled C- or D-check, but do not completely strip the paint during each cycle. Instead, they alternate between complete stripping and merely scuff-sanding the existing paint layer and applying a new topcoat. Painting costs include labor, stripper, paint, primer, masking materials, and proper disposal of consumables.

Airplanes should never carry more than two layers of paint. With more than two layers, operating efficiency drops, inspections become more difficult, and corrosion can start in chips that remain under a fresh topcoat. Excessive paint buildup is a particular concern on aging airplanes, as the buildup may cause difficulty during inspection of the rows of rivets and lap splices that connect fuselage panels.

Maintaining the appearance of a polished airplane requires repolishing up to three times a year with a special compound applied with mechanical buffers, as well as regular washing to clean oxidation buildup from unpainted surfaces. Both activities require a considerable investment in buffing equipment and personnel. Periodic maintenance can be performed while a polished airplane is being repolished, but not while a painted airplane is being stripped and repainted.

While the lighter weight of a polished airplane saves fuel costs, as shown in (table 1), this savings is more than offset by the higher cost of washing, polishing, and painting a polished fuselage throughout its service life (table 2). The net operating cost of polished airplanes, calculated as a percentage of the total operating cost, is between 0.06 percent and 0.30 percent more than the total operating cost of fully painted airplanes.

CORROSION PROTECTION
Polished and painted airplanes both need to be washed regularly to preserve their exterior surfaces. However, for the sake of appearance and image, it is not uncommon for polished airplanes to be washed twice as often as fully painted airplanes. Regular washing protects against corrosion by removing contaminants. It also gives maintenance personnel the opportunity to assess the surface condition of an airplane, which permits operators to predict the date and extent of future maintenance required for corrosion and erosion. A mild alkaline detergent and pure warm water should be used. It is particularly important to wash new airplanes, because the protective oxide film that naturally forms and grows on aluminum with age is relatively thin and provides little protection. Both painted and polished surfaces can be adequately protected from corrosion. Fuselage skins are made from Alclad aluminum that consists of a high-strength core alloy bonded to a thin layer of pure aluminum or aluminum alloy. Wing skins are made of bare aluminum and are protected by an impact-resistant paint system. Polished surfaces are protected from corrosion by regular buffing after washing. Painting protects against oxidation, salts, and jet fuel spills. However, unrepaired chips and cracks in paint collect dirt and moisture and so may become corrosion sites. Painted surfaces are also susceptible to filiform corrosion, or worm corrosion, which begins between metallic surfaces and paint and erodes both. It creates hydrogen and lifts up the paint layer as it travels across the surface. :banana :banana :banana
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nerys
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Grr

cool info billy508.

I just watched 714 of mythbusters where they "golfballed" an entire car. WOW that is cool! almost a 4mpg jump in economy! shows that while the golf ball has more parasite drag just that little reduction in base drag MORE than compensates for the parasitic drag.

I might have to see if I can find some way of doing that. One thing the mytbusters did not try and I think they should have is that I do not think you need to do the entire car like that. I think if you JUST did the back 25% of the roof and quarter panels and the trunk you would gain the same benefits with lower parasitic drag and lower mass. I just might have to try that on my metro. First I need to get it running smoothly and get a good baseline but that is VERY interesting. I can probably vacform something to keep the mass low. I wonder if REVERSE dimples will work ie BUMPS instead of dimples. I also wonder if SIZE of dimples is important.

IE when they did the car they massively upscales the dimples to match the size increase in scale. what if you use actual golf ball sized dimples?

VERY neat things to think about. Very fun episode :-)

a Dimpled kamback might be very interesting to try too.
Edited by nerys, Oct 31 2009, 10:15 PM.
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