Compulsory Aerodynamic Reading

Posted on April 24th, 2008 in Aerodynamics,Driving Emotion,Economy,electric by Julian Edgar

It’s happened only a few times in my life, and each time it’s been a salutary experience.


One occasion I can remember is a long time ago. I was in junior secondary school and was heavily into solar energy. I’d constructed my own solar water heaters, solar pie warmers and other bits of gear. I knew about meridian altitude, I knew about flat plate collectors and thermal mass.


I’d also read all the books I could get my hands on that dealt with solar heating and knew inside-out the (handful) of books on the topic in the school library.


In fact I was pretty smug about my level of knowledge and understanding.


Then a new book came into the library. I can even remember its size and shape – it was a book long in landscape direction and had soft covers. It was also quite thick.


I remember I picked this book and started looking through it with little interest. After all, I already knew everything about solar energy…


But, all of a sudden, I went very quiet and became intent. I was just about to discover a whole new world of solar energy complexity and relevance; my learning on the subject was going to progress hugely.


This book assumed all my knowledge and then took it far, far forward.


I permanently ‘borrowed’ it right up to the time I left school…


And then, just the other day, something similar happened. This time the topic wasn’t solar energy but car aerodynamics.


Car aero is a topic I’ve been teaching myself about for close to 20 years. Over that time I have built up a very good reference library on the topic – nine or ten books and as many engineering papers. (That doesn’t sound like much but there are simply not many books available.)


The best of those books is Aerodynamics of Road Vehicles, edited by W.H. Hucho. It was first published in 1987 but remains the ‘bible’ on the subject. Another really good book is Race Car Aerodynamics – Designing for Speed by J. Katz. This book was first published in 1995.


However, like many other aero references, Race Car Aerodynamics is – as its name suggests – is all about downforce and racing, rather than the aero of road cars. And the more you go into road car aero, the more you realise that conventional racing provides little relevant information…


Rather like solar energy a long time ago, I figured I had all the good gear on aero. I certainly don’t think that my knowledge of the subject is much more than infinitesimal, but by the same token, I didn’t think that there were many books around that I could use to extend my knowledge. (The more complex ones I simply can’t understand.)


And then it was suggested to me that I might want to read a book. Called The Leading Edge, it is subtitled Aerodynamic Design of Ultra-Streamlined Land Vehicles. It’s basically about the aero design of solar race cars; it was first published in 1999. The author is Goro Tamai.


I’d seen the book advertised but assumed it would be rather like the Katz book – good but not really relevant to road cars.


But then I borrowed The Leading Edge.




Talk about brilliant! Yes, The Leading Edge is primarily about solar racing cars. But in a way I don’t think the author really envisaged, it’s also shows the criteria that (some) cars of the near future will need to satisfy.


You see, to achieve an aero drag that’s a great deal better than current cars, the engineering aims need to change. No longer is pressure drag (ie the size of the wake) the critical factor, but instead skin friction and boundary layer effects become vital. ‘Wetted Area’ becomes damn-near as important as ‘Frontal Area’; cars slide through the air rather than punching holes in it.


By describing in detail the techniques required to achieve drag coefficients of way under half current cars, the author shows what characteristics those new cars will need to have. But it’s not all theory: the book also covers in excellent detail on-road (as well as wind tunnel) testing and development.


If you’re interested in car aero, The Leading Edge is not the right book to start with – instead read (or borrow) Hucho’s Aerodynamics of Road Vehicles. But if you want to go the next step in seeing where road car aero is heading, The Leading Edge is brilliant.


And if you’re building your own machine – whether that’s a Human Powered Vehicle, a one-off car, or a kit car – The Leading Edge is absolutely compulsory reading.



Footnote: if you read The Leading Edge make sure that you first download the corrections and updates here.

6 Responses to 'Compulsory Aerodynamic Reading'

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  1. Speedzzter said,

    on April 24th, 2008 at 8:37 am

    “Borrow” would be the key phrase as Amazon lists “The Leading Edge” at a startling $141.64 USD.

    BTW, Hucho’s 1987 edition of “Aerodynamics of Road Vehicles” is currently out-of-stock at Amazon. A 1998 edition published by the S.A.E. is available for $99.95 USD.

    Nobody ever said knowledge was cheap.

  2. Julian Edgar said,

    on April 24th, 2008 at 1:49 pm

    The Leading Edge is US$45 from its publisher –

  3. George Hawkins said,

    on April 25th, 2008 at 2:22 pm

    A lot of these aero ideas seem to depend on starting with smooth air. If the air is rough, lots of laminar flow designs look to be unworkable. Is that true? What would typical air roughness be for a road vehicle, especially in traffic? I have heard that the wind tunnel people were starting to work on that.
    George Hawkins

  4. Julian Edgar said,

    on April 25th, 2008 at 5:45 pm

    It’s a valid point.

    I can’t define ‘typical air roughness’ for you although I know that wind tunnel designers now strive to have some turbulence in their air flow. They do this especially for testing for wind noise.

    I have measured air pressures on a car that were differed depending on whether it was following another car.

  5. Stephen said,

    on May 6th, 2008 at 11:35 am

    What was the name of the solar energy book that caused you to “discover a whole new world of solar energy complexity and relevance” as I’m interested in reading it. Thanks, Stephen

  6. Julian Edgar said,

    on May 6th, 2008 at 11:38 am

    Um, that was 30 years ago! I don’t remember the title of the book and doubt now it would be considered anything special.