Mythbusters: Golf Ball Effect improves aerodynamics

[SLPinfo.org]

Hey folks,

Saw an episode of Mythbusters last night - they began by testing if a dirty
car gets better gas mileage than a clean car (based on the assumption of a
dirty car giving a "golf ball effect" - the dimples on a golf ball break up
the airflow and result in better aerodynamics).  Well the dirty car got
poorer gas mileage so the initial myth was busted.  BUT then they created a
car with a truly dimpled surface that looked a lot like that of a golf ball
(dimples enlarged to the scale of the car) and it improved gas mileage by
11% over a smooth surface on the same car.  Here's a link:

http://dsc.discovery.com/videos/mythbusters-dirty-vs-clean-car/

For those who are perhaps up to custom designs, making body panels with a
dimpled surface could potentially improve range.  Doing it on the sheet
metal of an existing car would be extremely difficult to do (as they
explained in the episode).  They used a clay material added to the outside
of the car for the test.


- Peter FLipsen Jr
http://www.evalbum.com/1974
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[AMPhibian]

Interesting.   A few months ago Pop Sci had an article about a company that made dimpled vehicle wraps claiming to increase mileage.  They failed to check with their sister publication Pop Mechanics who actually tested the same product earlier and found it did nothing.  The theory was that a golf ball works because it's spinning while a vehicle obviously does not, or if it does you have greater problems than mileage.  The dimpled wraps were rather shallow so maybe deeper contours would make a difference, though I'm still skeptical.

SLPinfo.org wrote:

Hey folks,

Saw an episode of Mythbusters last night - they began by testing if a dirty
car gets better gas mileage than a clean car (based on the assumption of a
dirty car giving a "golf ball effect" - the dimples on a golf ball break up
the airflow and result in better aerodynamics).  Well the dirty car got
poorer gas mileage so the initial myth was busted.  BUT then they created a
car with a truly dimpled surface that looked a lot like that of a golf ball
(dimples enlarged to the scale of the car) and it improved gas mileage by
11% over a smooth surface on the same car.  Here's a link:

http://dsc.discovery.com/videos/mythbusters-dirty-vs-clean-car/

For those who are perhaps up to custom designs, making body panels with a
dimpled surface could potentially improve range.  Doing it on the sheet
metal of an existing car would be extremely difficult to do (as they
explained in the episode).  They used a clay material added to the outside
of the car for the test.


- Peter FLipsen Jr
http://www.evalbum.com/1974
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[Roland Wiench]

I talk to my body man at the café this morning about this.  He said they put
in carbon fiber sections on a NASCAR race cars that does same effect.  I
also seen this dimple carbon fiber panels on jet fighters which reflect the
radar.

The Ferrari Contach Group 7 race car has this type of carbon fiber surface.

Another way to reduce the air resistance is to design the frontal section of
the vehicle wide open and duct it out over the vehicle.  He show me a Cam-AM
Group 7 race car that he is working on, it has the windshield and front
slope steep to 2 inches about the ground.

It has a 4 foot wide air opening that is ducted under the front end and exit
up over the wind shield.  These cars a mid engine, so the whole front end is
empty. This things only weighs 1300 lbs.

Roland


----- Original Message -----
From: "SLPinfo.org" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Thursday, October 22, 2009 9:58 AM
Subject: [EVDL] Mythbusters: Golf Ball Effect improves aerodynamics

> Hey folks,
>
> Saw an episode of Mythbusters last night - they began by testing if a
> dirty
> car gets better gas mileage than a clean car (based on the assumption of a
> dirty car giving a "golf ball effect" - the dimples on a golf ball break
> up
> the airflow and result in better aerodynamics).  Well the dirty car got
> poorer gas mileage so the initial myth was busted.  BUT then they created
> a
> car with a truly dimpled surface that looked a lot like that of a golf
> ball
> (dimples enlarged to the scale of the car) and it improved gas mileage by
> 11% over a smooth surface on the same car.  Here's a link:
>
> http://dsc.discovery.com/videos/mythbusters-dirty-vs-clean-car/
>
> For those who are perhaps up to custom designs, making body panels with a
> dimpled surface could potentially improve range.  Doing it on the sheet
> metal of an existing car would be extremely difficult to do (as they
> explained in the episode).  They used a clay material added to the outside
> of the car for the test.
>
>
> - Peter FLipsen Jr
> http://www.evalbum.com/1974
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[Peter Gabrielsson]

Myers motors has been using this effect on the NMG for a while:
http://tinyurl.com/yl9qhvf

And of course Homer Simpson is way ahead of the curve:
http://www.urbandictionary.com/define.php?term=speed%20holes

On Thu, Oct 22, 2009 at 9:58 AM, SLPinfo.org <[hidden email]> wrote:

> Hey folks,
>
> Saw an episode of Mythbusters last night - they began by testing if a dirty
> car gets better gas mileage than a clean car (based on the assumption of a
> dirty car giving a "golf ball effect" - the dimples on a golf ball break up
> the airflow and result in better aerodynamics).  Well the dirty car got
> poorer gas mileage so the initial myth was busted.  BUT then they created a
> car with a truly dimpled surface that looked a lot like that of a golf ball
> (dimples enlarged to the scale of the car) and it improved gas mileage by
> 11% over a smooth surface on the same car.  Here's a link:
>
> http://dsc.discovery.com/videos/mythbusters-dirty-vs-clean-car/
>
> For those who are perhaps up to custom designs, making body panels with a
> dimpled surface could potentially improve range.  Doing it on the sheet
> metal of an existing car would be extremely difficult to do (as they
> explained in the episode).  They used a clay material added to the outside
> of the car for the test.
>
>
> - Peter FLipsen Jr
> http://www.evalbum.com/1974
> -------------- next part --------------
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>
>

--
www.electric-lemon.com

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[Bill Dube]

If you place the "dimples" on the car in the correct areas, it will
work much better than dimples all over.

A golf ball has no front or back so you have to put the dimples
everywhere so there will be dimples in the area that you actually
need them to be.

With a car, you always travel in the same orientation, so you can put
the dimples where they help most, and not put dimples where they
would work against you.

They way they do this on gliders (and other aircraft) is to put drops
of used gear oil (cheapest, but you can use expensive colored fluids)
on the clean surface of the wings and body in the areas you guess
will go turbulent. (Like about 1/3 to 1/2 way along the chord of the
wing.) You then take the airplane for a flight. The oil drops turn
into streaks. Where the streaks go from a straight line to "mush" is
where you want to put a boundary layer "trip", (like a row of dimples.)

You actually want to place the trip just a bit ahead of the "mush".
They typically use a thick rough "vortex generator" tape to do this on gliders.

Picture and simple article:
http://www.deturbulator.org/Progress-OilFlows.asp

Here is a discussion thread showing the tape and the results:
http://ecomodder.com/forum/showthread.php/belly-pan-vortex-generators-1209-4.html

Complicated article:
http://en.wikipedia.org/wiki/Boundary_layer

Bill Dube'






At 10:58 AM 10/22/2009, you wrote:

>Hey folks,
>
>Saw an episode of Mythbusters last night - they began by testing if a dirty
>car gets better gas mileage than a clean car (based on the assumption of a
>dirty car giving a "golf ball effect" - the dimples on a golf ball break up
>the airflow and result in better aerodynamics).  Well the dirty car got
>poorer gas mileage so the initial myth was busted.  BUT then they created a
>car with a truly dimpled surface that looked a lot like that of a golf ball
>(dimples enlarged to the scale of the car) and it improved gas mileage by
>11% over a smooth surface on the same car.  Here's a link:
>
>http://dsc.discovery.com/videos/mythbusters-dirty-vs-clean-car/
>
>For those who are perhaps up to custom designs, making body panels with a
>dimpled surface could potentially improve range.  Doing it on the sheet
>metal of an existing car would be extremely difficult to do (as they
>explained in the episode).  They used a clay material added to the outside
>of the car for the test.
>
>
>- Peter FLipsen Jr
>http://www.evalbum.com/1974
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[Dave Hymers]

Wow, thanks Bill, that's an eye opener. Very interesting.
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[Lee Hart]

AMPhibian wrote:
> A few months ago Pop Sci had an article about a company that
> made dimpled vehicle wraps claiming to increase mileage.  They failed to
> check with their sister publication Pop Mechanics who actually tested the
> same product earlier and found it did nothing.  The theory was that a golf
> ball works because it's spinning while a vehicle obviously does not, or if
> it does you have greater problems than mileage.  The dimpled wraps were
> rather shallow so maybe deeper contours would make a difference, though I'm
> still skeptical.

You need to understand what the dimples do, and why they work. You can't
just blithely apply them any old way and expect good results.

The dimples need to be placed just behind the widest cross-section of
the object, right at the point where the laminar airflow would have
detached and become turbulent. By triggering lots of small points of
turbulence, you avoid creating a much larger turbulence.

A golf ball has dimples everywhere because it rotates. If you prevent it
from rotating (gyroscope inside, etc.) then adding dimples just behind
the widest point reduces the drag by the largest amount.

Since it spins, they have to put dimples everywhere. The dimples on the
front and back surfaces *add* drag. But it turns out that they add less
drag than the dimples around the widest point remove; so you come out ahead.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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[Mike Willmon]

Bill,
  Those equations look hauntingly familiar.  In fact I think Maxwell
actually derived his equations from the mathematical work already done
in the field of fluid dynamics.  Which lends credibility of the phrase
"the water pipe theory of electronics"  ;-)

But on the larger airliners though they also do this with those fin
looking vortex generators, but basically the same concept right.  Make
it slightly turbulent and the flow won't separate.  But without them the
flow gets so turbulents and large sparations in the laminar flow occur.

I wonder if any of the LSR racers are employing this degree of aero
enhancements?

Mike


On Thu, Oct 22, 2009 at 10:26 AM , Bill Dube wrote:

> If you place the "dimples" on the car in the correct areas, it will
> work much better than dimples all over.
>
> A golf ball has no front or back so you have to put the dimples
> everywhere so there will be dimples in the area that you actually need
> them to be.
>
> With a car, you always travel in the same orientation, so you can put
> the dimples where they help most, and not put dimples where they would
> work against you.
>
> They way they do this on gliders (and other aircraft) is to put drops
> of used gear oil (cheapest, but you can use expensive colored fluids)
> on the clean surface of the wings and body in the areas you guess will
> go turbulent. (Like about 1/3 to 1/2 way along the chord of the wing.)
> You then take the airplane for a flight. The oil drops turn into
> streaks. Where the streaks go from a straight line to "mush" is where
> you want to put a boundary layer "trip", (like a row of dimples.)
>
> You actually want to place the trip just a bit ahead of the "mush".
> They typically use a thick rough "vortex generator" tape to do this on
> gliders.
>
> Picture and simple article:
> http://www.deturbulator.org/Progress-OilFlows.asp
>
> Here is a discussion thread showing the tape and the results:
>
> http://ecomodder.com/forum/showthread.php/belly-pan-vortex-generators-1209-4.html
>
> Complicated article:
> http://en.wikipedia.org/wiki/Boundary_layer
>
> Bill Dube'
>
>
>
>

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[SLPinfo.org]

Re:  dimple size.  They scaled the dimples up from the proportions of the
golf ball to the size of the car.  The dimples were quite noticable - if I
had to guess they were about the size of half a baseball.  I have to believe
that the golf ball companies have figured out precisely how big the dimples
should be and scaling up would be an appropriate thing to do.

Re:  dimple placement.  They observed a noticable positive effect by putting
dimples everywhere.  Given their findings, then if Bill and Lee are right,
selective placement of the dimples would result in even better fuel
efficiency than the 11% they found!  All the more reason to at least
consider them in vehicle design.

- Peter Flipsen Jr




On Thu, Oct 22, 2009 at 1:30 PM, Lee Hart <[hidden email]> wrote:

> AMPhibian wrote:
> > A few months ago Pop Sci had an article about a company that
> > made dimpled vehicle wraps claiming to increase mileage.  They failed to
> > check with their sister publication Pop Mechanics who actually tested the
> > same product earlier and found it did nothing.  The theory was that a
> golf
> > ball works because it's spinning while a vehicle obviously does not, or
> if
> > it does you have greater problems than mileage.  The dimpled wraps were
> > rather shallow so maybe deeper contours would make a difference, though
> I'm
> > still skeptical.
>
> You need to understand what the dimples do, and why they work. You can't
> just blithely apply them any old way and expect good results.
>
> The dimples need to be placed just behind the widest cross-section of
> the object, right at the point where the laminar airflow would have
> detached and become turbulent. By triggering lots of small points of
> turbulence, you avoid creating a much larger turbulence.
>
> A golf ball has dimples everywhere because it rotates. If you prevent it
> from rotating (gyroscope inside, etc.) then adding dimples just behind
> the widest point reduces the drag by the largest amount.
>
> Since it spins, they have to put dimples everywhere. The dimples on the
> front and back surfaces *add* drag. But it turns out that they add less
> drag than the dimples around the widest point remove; so you come out
> ahead.
>
> --
> Lee A. Hart             | Ring the bells that still can ring
> 814 8th Ave N           | Forget the perfect offering
> Sartell MN 56377        | There is a crack in everything
> leeahart earthlink.net  | That's how the light gets in -- Leonard Cohen
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
>

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[Bill Dube]

I would guess that the energy savings could be in the range of 5% to
10% at highway speeds with proper placement on a nice slick car.

I don't think you will do much better than that.

Bill D.

At 03:34 PM 10/22/2009, you wrote:

>Re:  dimple size.  They scaled the dimples up from the proportions of the
>golf ball to the size of the car.  The dimples were quite noticable - if I
>had to guess they were about the size of half a baseball.  I have to believe
>that the golf ball companies have figured out precisely how big the dimples
>should be and scaling up would be an appropriate thing to do.
>
>Re:  dimple placement.  They observed a noticable positive effect by putting
>dimples everywhere.  Given their findings, then if Bill and Lee are right,
>selective placement of the dimples would result in even better fuel
>efficiency than the 11% they found!  All the more reason to at least
>consider them in vehicle design.

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[todd]

I've been soaking up all the excellent information here for over a year and this topic actually falls within my area of expertise. So, at the risk of getting too far off topic, just some quick trivia. The dimples on the golf ball got their start way back when golfers noticed that their (Very expensive) leather balls, stuffed with feathers, flew farther after they became scuffed up a bit. The next generation of cheaper balls (Gutta-percha) saw the use of grooves which lead to dimples.  

I just painted my Electercel and ended up with a bad case of orange
peel...So should I buff it out or leave it for the dimple effect :)


Buddy Mills
[hidden email]
 
Look mom, no gas. http://www.evalbum.com/2887

Disclaimer:  No animals were harmed or killed in the process of writing this
email.  Any stories to the contrary are, for the most part, either fictional
or greatly exaggerated.



-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of SLPinfo.org
Sent: Thursday, October 22, 2009 12:58 PM
To: Electric Vehicle Discussion List
Subject: [EVDL] Mythbusters: Golf Ball Effect improves aerodynamics

Hey folks,

Saw an episode of Mythbusters last night - they began by testing if a dirty
car gets better gas mileage than a clean car (based on the assumption of a
dirty car giving a "golf ball effect" - the dimples on a golf ball break up
the airflow and result in better aerodynamics).  Well the dirty car got
poorer gas mileage so the initial myth was busted.  BUT then they created a
car with a truly dimpled surface that looked a lot like that of a golf ball
(dimples enlarged to the scale of the car) and it improved gas mileage by
11% over a smooth surface on the same car.  Here's a link:

http://dsc.discovery.com/videos/mythbusters-dirty-vs-clean-car/

For those who are perhaps up to custom designs, making body panels with a
dimpled surface could potentially improve range.  Doing it on the sheet
metal of an existing car would be extremely difficult to do (as they
explained in the episode).  They used a clay material added to the outside
of the car for the test.


- Peter FLipsen Jr
http://www.evalbum.com/1974
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[Curtis Keller]

Saw the same episode.   Kind of ugly car with the dimple features - but it
does prove that smooth is not necessarily the most aerodynamically slick.


I was hoping for a test of the car w/ a supersized SPEEDO LZR RACER suit for
the car.

On Thu, Oct 22, 2009 at 11:58 AM, SLPinfo.org <[hidden email]> wrote:

> Hey folks,
>
> Saw an episode of Mythbusters last night - they began by testing if a dirty
> car gets better gas mileage than a clean car (based on the assumption of a
> dirty car giving a "golf ball effect" - the dimples on a golf ball break up
> the airflow and result in better aerodynamics).  Well the dirty car got
> poorer gas mileage so the initial myth was busted.  BUT then they created a
> car with a truly dimpled surface that looked a lot like that of a golf ball
> (dimples enlarged to the scale of the car) and it improved gas mileage by
> 11% over a smooth surface on the same car.  Here's a link:
>
> http://dsc.discovery.com/videos/mythbusters-dirty-vs-clean-car/
>
>

--
Curtis Keller
[hidden email]
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[Jon Glauser-2]

On Thu, Oct 22, 2009 at 9:40 PM, Curtis Keller <[hidden email]> wrote:
> I was hoping for a test of the car w/ a supersized SPEEDO LZR RACER suit for
> the car.

Indeed, that would be supremely awesome! :D


-Jon Glauser
http://jonglauser.blogspot.com
http://www.evalbum.com/555

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