Matt Russell + Omni in the Wind Tunnel
article & images by Nick Salazar
Mar 19, 2019
With limited time in the wind tunnel, test design has to be quite judicious and deliberate. We went into the tests with Matt wanting to answer two primary questions. First, how does Matt's new Omni compare to his old rig, and second, will tilting Matt's hands have a noticeable effect on drag?
We teased this out in two ways. First, bike-only tests show that indeed, the Omni as a complete bike creates far less drag than Matt's complete setup from 2018, at every yaw angle tested.
Once Matt got on board, the results got even more interesting. Not only did we manage to find almost 10 Watts of free speed, but that speed depended quite sensitively to his arm angle. Moreover, we significantly reduced the amount of side force he has to battle while riding. Let's dive into those results a bit more closely.
Omni vs Old Rig
In comparing the baseline setups, we have a clear and consistent advantage to the new rig. This is what we expected, as we've significantly reduced the frontal area, as well as the gaps between disparate components at the front end. The Omni's Monofoil design presents a single, continuous airfoil to the wind, allowing the clean air that hits the front of the head tube (or Universal Cover, in this case) to flow smoothly and cleanly all the way back to the rear wheel. Traditional double-diamond bikes can't enjoy that kind of clean path for the air, no matter how efficient their shapes get.
It's worth noting that Matt's nutrition and storage needs haven't been compromised either. He will run a single bottle between the arms, or potentially a double bottle (one in front of the other, Rinny style). Then he'll run one or two bottles in back, courtesy of our Beta carrier and Kappa cages. (Those rear cages were left off of this test for the sake of simplicity, and would be more or less equivalent whether run on the Omni or the Diamondback.) The Omni's storage box, just behind the stem, remains available to hide his BlipBox, as well as holding gels or other small items. Matt doesn't always run a spare tire or flat kit, but those could easily be stored between his saddle rails, leaving nothing exposed to the wind.
Matt has a very dialed, aggressive, aero position, from which he can generate quite a bit of power. He's an excellent biker. There's very little low-hanging fruit here, I daresay none. Matt's biggest question was whether tilting his hands upward would be of any use. This is a question that can only be answered definitively in a wind tunnel. And in fact, the answers we got are something you could not guess. At his baseline position, which basically replicated his old hand position, the Alpha One's tilt read 5 degrees upward. So, we started running tests, increasing the tilt by 2.5 degrees each time, and continued until we maxed out the range of the bar.
The results here are striking. The move from 5 to 10 degrees results in a very large drag INCREASE, then drag just plummets as we continue increasing the tilt angle. In part, this may have to do with the way the wind flows over Matt's body. He's 'closing the bag' as they say, preventing wind from coming in towards his torso and getting caught around his hips. Instead, he is simply punching through the wind in a more continuous shape. But there's another aspect here which is that he settles into his aero tuck a little more aggressively, without feeling that he's aggressive. He is just more naturally tucking in. In fact, Matt reported feeling more comfortable with the tilt up, and didn't feel like he had to think about his head at all.
The difference in appearance is subtle, but the difference in drag was significant. But the outlier - the 10-degree position - illustrates why things like hand tilt can't be left up to guesswork or 'best practices.' There's simply no substitute for doing the test and finding out what actually works for the individual rider. And again, this is where Alpha One shines. Our setup time between runs was under 2 minutes, meaning we were able to get more tests done with our limited tunnel time. We didn't change Matt's stack at all during these tests, but in a future session I would be tempted to drop him just a smidge, to see if we can get that CdA even just a little bit lower, without sacrificing his comfort or power.
This isn't to say we've discovered a "rule" for tilt angles. Just the opposite. We've found that for this individual rider, on this rig, 5 degrees was good, 10 degrees was bad, and 15-17.5 degrees was excellent. So what's the advice for the age grouper who can't run these tests in a tunnel? Do whatever is most comfortable. That will likely be the most powerful position, even if it isn't the fastest.
But when mining the data a bit further, we found something we weren't even looking for, and it's pretty powerful stuff. Hit the jump for more.
Although they might not be so exciting at first glance, these graphs are the real treasure of our time at the tunnel. The two big takeaways are that, with the new equipment and position, Matt will save nearly 10 Watts compared to his previous rig, meaning that for the same power output, he could go approximately 3 MINUTES FASTER over the course of an Ironman bike leg. Second, we've significantly reduced the side force and handling torque he experiences in the wind, meaning he can spend more of his energy going forward, rather than fighting the wind's effects on bike handling.
Matt is a consummate professional. Not only does he have a very detail-oriented mind, but he can pedal in the tunnel with a stillness that makes the data very clean. Most athletes will move or fidget just a bit, causing the data readings to jump around somewhat. That's why you have to take very long data samples with a rider on board (the tunnel recommends 60 seconds per point). But with Matt, he's such a smooth pedaler that we were able to shorten the sample rate to 40 seconds per point, and still get very consistent data.
This test rig is set up exactly like Matt's rig back at his home in Florida. Because Omni and the Alpha One aerobar are so easy to adjust, it took us all of two minutes to set the bike to Matt's exact position. It was just a matter of setting the Monopost position, the tilt angle, and then the seatpost/saddle. Five bolts. Running through different hand positions was also a breeze, just two bolts to loosen, set tilt, and tighten again. The staff at the tunnel said we were perhaps the most efficient crew they had seen.
San Diego LSWT
Some shots of the facility and instruments at the San Diego Low-Speed Wind Tunnel, as well as a couple of those of Matt's prior bike that we used for comparison purposes.