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Old 04-13-2012, 08:29 PM   #311 (permalink)
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The flow is probably fine because it's hardly ever in ground effect thus the body can have a fineness ratio half of what we're used to.

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Old 04-13-2012, 08:42 PM   #312 (permalink)
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Quote:
Originally Posted by aerohead View Post
If an auto maker wants to brag they'll quote the zero-degree drag coefficient.Some companies test for yaw and report a crosswind-averaged Cd.
In 1987,the Arivett Brothers designed a streamlined Top Fuel dragster which had Cd 0.20 at zero-degrees and Cd 0.18 at 12-degrees of yaw.The best funny cars of the day were measuring at around Cd 0.60.
I'll be posting some 'streamlined' cars of the past,soon I hope,and you'll see that some were designed for plan-view,with fineness ratios which would mimic a streamlined section,rather than a streamlined body of revolution.
A section of 3.92:1 has the lowest drag,so the boat tail angles are more generous.

Hmmmm...... I think we have a different objective. I am after BUILDING a car. I am looking for information to help me build my cars.

For my purposes, 22 is not an acceptable number as I don't think it will work in the real world.

And I don't have a windtunnel, so I'm after something pretty simple to implement.
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Old 04-14-2012, 01:41 PM   #313 (permalink)
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Originally Posted by drmiller100 View Post
Hmmmm...... I think we have a different objective. I am after BUILDING a car. I am looking for information to help me build my cars.

For my purposes, 22 is not an acceptable number as I don't think it will work in the real world.

And I don't have a windtunnel, so I'm after something pretty simple to implement.
If you're going to scratch-build a body-in -white car I would recommend you not begin until you have thoroughly read about Eiffel,Rumpler,Jaray,Lay,Fachsenfeld,Kamm,Hoerner, Korff,Mair,Morelli,and studied what VW,Mercedes-Benz,GM,Ford and others have done with their record cars over the years.
All of this body of work will be necessary for you to have enough tools to work with .
I've been actively involved in road vehicle aerodynamics since 1974 and it's taken this long to arrive at a fabrication tool as simplified as the 'Template'.
Perhaps your research will uncover something hundreds of other investigators have missed over the last 90-years of active wind tunnel research.
You'll want to have your car fully constructed and tested on paper before you purchase an ounce of material or consume a Watt of energy.
Sorry I couldn't help.
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Old 04-14-2012, 10:11 PM   #314 (permalink)
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Quote:
Originally Posted by aerohead View Post
I would recommend you not begin until you have thoroughly read about Eiffel,Rumpler,Jaray,Lay,Fachsenfeld,Kamm,Hoerner, Korff,Mair,Morelli,and studied what VW,Mercedes-Benz,GM,Ford and others have done with their record cars over the years.
If one sought only a single book on the topic, it would be the Hucho book everyone keeps mentioning, right?
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Old 04-15-2012, 01:50 PM   #315 (permalink)
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Quote:
Originally Posted by aerohead View Post
If you're going to scratch-build a body-in -white car I would recommend you not begin until you have thoroughly read about Eiffel,Rumpler,Jaray,Lay,Fachsenfeld,Kamm,Hoerner, Korff,Mair,Morelli,and studied what VW,Mercedes-Benz,GM,Ford and others have done with their record cars over the years.
All of this body of work will be necessary for you to have enough tools to work with .
I've been actively involved in road vehicle aerodynamics since 1974 and it's taken this long to arrive at a fabrication tool as simplified as the 'Template'.
Perhaps your research will uncover something hundreds of other investigators have missed over the last 90-years of active wind tunnel research.
You'll want to have your car fully constructed and tested on paper before you purchase an ounce of material or consume a Watt of energy.
Sorry I couldn't help.
I doubt I'm smarter then you. And I'm not going to spend 40 years reading about stuff.

It is a shame you can't help me build anything better then a stock 1994 suburban.

I'll just have to stumble along without all the required engineering research.
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Old 04-15-2012, 01:55 PM   #316 (permalink)
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Originally Posted by drmiller100 View Post
I doubt I'm smarter then you. And I'm not going to spend 40 years reading about stuff.

It is a shame you can't help me build anything better then a stock 1994 suburban.

I'll just have to stumble along without all the required engineering research.
Build in as much plan taper as you can. Follow the template as much as you can. It really is this simple and he already did all that work.
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Old 04-15-2012, 04:00 PM   #317 (permalink)
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I dont agree 100% with aerohead on this reading stuff. Its good to read lots of books and previous studies but there is always coming new and better info which might disagree with the old data. So when should you start building and testing a new car model? I would say right now. You do learn every day, week or month new things about aerodynamics but then you can improve the already good model you have manufactured.

Here I like to thank Aerohead from that Template and ERTW for those neat simulations.

You do need to take a look of those cars aerohead mentioned and also few never ones, but you dont need to be a aerodynamic mastermind to make a car which Cd is under 0.2. Ofcourse it depends on the goals also, but then you just need to pick a vehicle that is closest to your target Cd and make few modifications to it.
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Old 04-15-2012, 04:42 PM   #318 (permalink)
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Quote:
Originally Posted by Vekke View Post
I dont agree 100% with aerohead on this reading stuff. Its good to read lots of books and previous studies but there is always coming new and better info which might disagree with the old data. So when should you start building and testing a new car model? I would say right now. You do learn every day, week or month new things about aerodynamics but then you can improve the already good model you have manufactured.

Here I like to thank Aerohead from that Template and ERTW for those neat simulations.

You do need to take a look of those cars aerohead mentioned and also few never ones, but you dont need to be a aerodynamic mastermind to make a car which Cd is under 0.2. Ofcourse it depends on the goals also, but then you just need to pick a vehicle that is closest to your target Cd and make few modifications to it.
vekke, you misunderstood Phil's point. there was a great deal of sarcasm in it.
He has done this and compiled the data, and was more than a little pissed that somebody would disagree out of hand with absolutely no scientific support whatsoever.
He presented the template, put it out there as one the best shapes for aero vehicles.
ERTW recently proved it out for us all.
I know I will not have as much plan taper in my design as I would like, but it will have as much taper as I can get. It only makes sense to reduce that base drag as much as possible. The aerocivic and all the other rigs, all the record setters do so.
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Old 04-15-2012, 05:16 PM   #319 (permalink)
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Quote:
Originally Posted by drmiller100 View Post
I doubt I'm smarter then you. And I'm not going to spend 40 years reading about stuff.

It is a shame you can't help me build anything better then a stock 1994 suburban.

I'll just have to stumble along without all the required engineering research.
I can understand your impatience to get started, but your building effort will be long, and expensive. Why not try to understand the aerodynamic principles first. Mistakes will be expensive and time consuming to correct. Phil has put an engineering lifetime into trying to understand the principles.

Probably the best way to get a very quick education is to get your hands on a copy of Hucho's book. Most of the main principles, as they apply to cars, are discussed in just a couple of chapters of his book, complete with graphs. He has lots of equations, but you can get most of the information by just looking at his graphs. A required read, as a minimum, before you spend money or effort.
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Old 04-15-2012, 05:48 PM   #320 (permalink)
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Originally Posted by jimepting View Post
I can understand your impatience to get started, but your building effort will be long, and expensive. Why not try to understand the aerodynamic principles first. Mistakes will be expensive and time consuming to correct. Phil has put an engineering lifetime into trying to understand the principles.

Probably the best way to get a very quick education is to get your hands on a copy of Hucho's book. Most of the main principles, as they apply to cars, are discussed in just a couple of chapters of his book, complete with graphs. He has lots of equations, but you can get most of the information by just looking at his graphs. A required read, as a minimum, before you spend money or effort.
Yes, this is good advice. When lovemysan made a belly pan, the work was impeccable ...

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... but execution details ended up hurting his aero. I think he was able to fix it, but it was discouraging at first to see all that work cost him MPG. He eventually dumped it :

http://ecomodder.com/forum/showthrea...ity-13699.html

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