One of the pleasures of an interest in aerodynamics is the opportunity on offer to get things very wrong. My favourite example of getting it wrong comes not from cycling (we’ll get to that in a moment), but from that bastion of aerodynamic expertise, F1.
F1 teams have been wind-tunnel testing for decades. Until the FIA stopped them, some bigger teams were running multiple tunnels, often for 24-hours a day. For most of that period, all the testing was done in zero-yaw, wind from dead-in-front conditions, on the basis that if your car does 300 kph, the impact of any crosswind will be almost unmeasurably small.
Until one day someone new to the whole area pointed out that most aerodynamics in F1 is concerned with improving cornering grip, and a car in mid-corner is experiencing quite high yaw because it’s going partly sideways. So given that, they asked, why didn’t they test cars at going-round-a-corner type yaw angles?
There was, by all reports, quite a lot of foot-shuffling, followed by some new yaw-angle protocols. One engineer I knew who was in F1 in that era just said, “I felt like the dummy of the year.”
Mistakes are easy to make, which is why we refer to them as “making progress”.
There are plenty from the cycling world. More of ours have had to do with simply not making enough measurements or not making them accurately enough. But there have been a lot that relied on erroneous assumptions as well.
For literally decades we assumed that wrinkles on a skinsuit were an aero disaster. So, therefore, it was vital to wear a very tight suit to stretch the wrinkles out. I found a video of myself from recently as 2013 telling someone about just how small a suit a pro rider would be prepared to squeeze into. Even when we’d started doing skinsuit research a few years previously it had been taken as a given that you started out with as tight a suit as you could, and only then started looking at seam patterns, aero trips and the like.
A few years later? Well, by then we’d worked out that you might get rid of the wrinkles, but fabrics respond differently with different degrees of stretch. A lot of Lycra fabrics, when you stretch them, get slower. (At least a certain speeds, just to complicate matters.) It’s probably because the porosity of the fabric changes. General advice now, for most suits, is to wear as large as you can without too many wrinkles. And, I’ll just mention in passing, there are a few spots on a suit where wrinkles might actually make you go faster.
At an even more basic level, it might seem obvious now that Lycra is faster than skin. It didn’t seem obvious until someone proved it. Proving it involved people doing runs in a wind tunnel in the nude. Even if you shave every hair off your tunnel rat, it’s still (thankfully) faster if it’s got a suit on.
The retrospective irritations of that are considerable for those of us who avoided wearing socks, for example, or specified suits with very short shorts or very short arms on the basis that Lycra must be slower than skin because…. Well, there was no good reason for the assumption at all. It just seemed like common sense, and everything that seems like common sense should be treated with deep suspicion where aerodynamics is concerned.
Another bit of common sense was that the lowest riding position was also the fastest. Even if most of us gave lip service to the need for a compromise that allowed you to still produce enough power through the pedals, it was still a given that you should always be working to get the bars as low as possible. The idea that you might simply be more aerodynamic sitting higher (and I know several riders who are) was a ludicrous a suggestion as the idea of wearing a suit that allowed you to breathe.
The reason for that mistake was simple – in general photographs of bike riders were taken side-on, especially the sort of images you might look at to see the details of someone’s set up. From the side, the main difference isn’t about frontal area, which actually affects drag, it’s simply how low the position is. For the late 1990s and 2000s, most of the side-on pictures were of Chris Boardman. He was the first rider widely known to have seen the inside of a wind tunnel, so his aero decisions were scrutinised very closely indeed.
Boardman had an insanely low position, founded entirely on the fact he was (and I don’t think he’d mind my saying this) a slightly funny shape. He had a long back, relatively short legs and a good level of flexibility, so super-low came quite naturally to him, and worked well. Normally-shaped people had no business trying to copy him, but they did.
Scientifically inclined riders were not averse to putting a clear acetate sheet over a photo of a star rider like Boardman and marking it up to compare with their own. No one ever seemed to look at the question of how high they might be able to get off with from an aero point of view, it was always how low you could get off with from a biomechanical point of view.
There was another Boardman characteristic that became even more dominant than height – by the mid 2000s we’d kind of got over that. He also gave us the flat forearm position. Before he’d been involved in proper testing, like most others of his era Boardman had ridden with his forearms sloping upwards and his hands in front of his chin. For him, in the tunnel, flat arms presumably worked better, since he switched and never went back.
It took nearly twenty years, until around 2010, for us to work out that almost all the rest of us would have been better copying his first position. For the entire time in between, with one or two exceptions like Floyd Landis (and me, getting it right for once), everyone rode flat-armed. It was so standard that most aerobars didn’t even adjust to allow anything else.
Flat was “obviously” faster, because your arms were in line with the airflow. Except it wasn’t. The flow isn’t necessarily horizontal at that point, because it’s already being influenced by you and your bike. Not only that, but for most people an upward sloping arm position allows a narrower shoulder position and a lower head carriage, both of which are generally quicker.
What all of these examples have in common is that they were just assumed to be right, by everyone. It’s very easy to be critical in hindsight, easy to say that you shouldn’t make assumptions. You should always test, you should always have the imagination to think of different ways of doing things.
It’s harder in practice. Otherwise there wouldn’t be such a lucrative and eternally-renewing market for experts to write books and give talks telling you how to behave like that. People accept commonly-shared assumptions without even noticing that they’re doing it.
It takes a lot of imagination to get past that. It also needs some reliable, inexpensive way of testing your outside-the-box brainwaves. But that’s a story for a different blog.