My brother recently wrote a blog post on the Driving Progression, which is a Dunning-Kruger of performance driving. I thought it would be fun to the do the same thing for aerodynamics.
If you don’t know what the Dunning-Kruger effect is, it’s that people with very little knowledge have a lot of confidence. They’ll freely share the benefit of their inexperience with everyone. As they gain knowledge, they start to realize they don’t know anything, and lose confidence, eventually reaching a low point of “I don’t know shit.” After hitting rock bottom, an increase in knowledge steadily rebuilds confidence to the point that they master the topic.
The D-K effect is not about being stupid, it’s about not knowing any better. That’s certainly how I started my journey through aerodynamics, and it’s probably similar to how other people got started.
I’ve identified four general stages of the D-K effect, which I’m calling Fanboi, Learning, Experiments, and Optimization.
- Fanboi – Buying aero parts for looks, drag reduction, or blind trust.
- Learning – The apple of knowledge brings despair.
- Experiments– Tools and experiments to expand knowledge.
- Optimizations – Applying aerodynamic principles to any object with good results.
Fanboi
The first phase of aerodynamics is largely acquiring parts without understanding their specific use.
- Appearance – Many people buy aero parts because they look cool. Most dealer options like a front lip, side skirts, or spoiler are early on the upward slope.
- Drag reduction – People easily grasp the concept of drag reduction, and not knowing any better, it defines the next level of purchases or DIY projects.
- Blind trust – At this point a person has bought a wing or spoiler and some other aero that has good results (I dropped 3 seconds with a wing!), and now they think more aero is better and buy it all, whether or not it’s designed well or would be useful on their car.
The peak of the “acquiring without understanding” phase is probably canards. People who buy them don’t know why they’d want to spin a vortex on the side of the car, and often don’t have underbody aero anyway.
You can ask a fanboi why they have this aero part, or how it works, and you’ll get a reply that has nothing to do with personal aero knowledge and everything to do with blind trust in the manufacturer. Businesses have a vested interest in parting you with your money, are they really the people you should trust on this matter?
Some people never get past the Fanboi phase, and good for them, ignorance is bliss. But some of them watch a video or read a book, or god forbid they find this website, and then they fall down a very deep hole into despair.
Learning
The next phase begins when a person does actual research into aerodynamics, and thus begins a slippery slope down Dunning-Kruger’s backside. Often YouTube is their first inkling that things don’t work exactly the way they’d hoped. For example, maybe they saw Kyle Forster’s video on how wings don’t work with convertibles. Or they watch Julian Edgar read yet another bedtime story from his book.
Some people might stumble onto my Occam’s Racer website, and if you’re a regular reader, you know I do a lot of debunking and peeking behind the curtain. Other notable stops on the way to the pit of despair include Competition Car Aerodynamics, by MacBeath and Race Car Aerodynamics, by Katz.
From there you might dig deeper into to the grandfather of texts, Hucho’s Aerodynamics of Road Vehicles, or hit the lowest point, SAE papers and peer-reviewed university studies. At this point aerodynamics, or should I say, fluid dynamics, is so full of numbers, equations, and nerd stuff that you feel you know shit-all of nothing.
Experiments
Further knowledge comes through experimentation. Just as you were once a fool to trust aerodynamics manufacturers, you’d be a fool to trust anything you read or see on YouTube. So this next phase is where you get hands-on, experimenting to see the result.
Personally I jumped right into Airfoil Tools, OptimumLap, and other free resources, then DIY’d my own projects. A more sensible approach, and one I took later, is to enroll in Kyle Forster’s (JKF Aero) online course on aerodynamics.
Most of us aren’t going to have the means to get into CFD, and so Kyle does that for you, performing the experiments you’d do, and doing a nose-to-tail breakdown of CFD. If you are serious about aero, there’s no better use of your time or money.
It’s worth noting that Kyle uses OptimumLap in his course, since it’s a great way to get instant validation on whether something works or doesn’t, and how it plays out on different race tracks. I was already using the program for years before taking Kyle’s course, and it being FREE, everyone who is serious about aero or validating any other modifications to their car should use it.
The final stop in the Experiments stage is oddly where I started: real-world testing. That could mean going to a wind tunnel, or in my case, hiring a professional to make Watkins Glen into our own personal wind tunnel. And with that hard data, one comes to certain realizations about aero, and it turns out that it’s not that difficult after all.
Optimizations
Once you reach this level of understanding, you realize it’s not about the parts, but by applying certain principles. You are either optimizing the car for a particular rule set, or in the absence or racing rules, to handling characteristics, efficiency, a particular race track, or other factors.
The principles go something like this:
- Attached flow – You want to keep air attached along surfaces. A thicker and turbulent boundary layer is better than detached. Streamlined objects have rounded leading edges. Break cleanly at the trailing edge.
- Change the direction of air – If you aren’t changing the direction of airflow, you aren’t doing dick. Most often you want to send air upwards, creating an opposing force: downforce. You don’t want to change direction too much or air detaches, causing drag and destroying downforce.
- Maximize suction – Pressure is good, suction is better. Maximize suction and minimizing losses to the underside of splitters, underbody, and wings.
- Manage tires – Tires are draggy disruptive to airflow, creating a jet of air as they contact the ground. Manage tire drag and squirt to mitigate losses.
- Manipulate vortices – Vortices are usually thought of in terms of loss and wasted energy, but you can manipulate vortices to create air fences, delay flow separation, reduce energy on the face of the tire, etc. At the bleeding edge of performance, like F1, it seems like most of the effort is spent managing and manipulating vortices.
Conclusion
There is nothing wrong with being on the early, upward slope of the Dunning-Kruger graph. Choosing aero parts because you like the way they look, or because you support a particular manufacturer, or because they work and you don’t care why, is a happy place to be. This covers the 90% usecase.
In reflection, I can’t think of a compelling reason to get into early aerodynamic texts or plunge into SAE papers, they can be too much. Instead, leave that shit to me, I’ll translate it for the masses and make it fun to read (I won’t say “dumb it down” because y’all are smart or you wouldn’t be here).
But if you really want to get into aerodynamics because you’re developing something for the last 10% of performance, or because you need a competitive edge, then I’d start with the JKF aero course. You’ll definitely be making your own aero parts, because the aftermarket doesn’t support the kinds of things you’ll be doing, so plan on investing in tools and materials.
This is a worthy journey, but all-consuming, and requires sacrifices. Have fun with it.
Occam's Racer 