Introduction
With aerodynamic drag being the largest force an athlete has to overcome, finding ways to minimise this is always a major objective for competitive riders in cycling and triathlon. In this case study, we’re focusing in particular on the performance of an athlete’s custom-fit Vorteq skinsuit.
Clothing used to be overlooked in the world of aerodynamic optimisation, but with increasing knowledge around fabric properties and the way air flows around a complex, organic shape like a human being, we’re now able to develop and refine sportswear in a way that can provide a significant performance advantage.
The Vorteq Process: custom-fit clothing
The start point for our project with Michael was the 3D scan, which we use to capture a virtual model of the athlete whilst in their race position. Rather than taking simple cross-section measurements at different points in the body, this is a far more accurate means of capturing a rider’s physiology in the position that matters most. It’s this stage that allows us to create the pattern for the suit and the overshoes that are completely bespoke to the scanned rider (as opposed to a scaled standard pattern).
Once we had created the pattern with Michael’s own artwork design mapped on to it, the suit and overshoes were constructed and put through quality control in the Vorteq manufacturing lab.
Wind Tunnel testing at the Silverstone Sports Engineering Hub (SSEH)
The objective for Michael was a straightforward one to establish the performance difference between his current optimised setup and his new Vorteq skinsuit and overshoes. Specifically, we’re looking at the difference in drag (CDA) between the different runs:
CDA = (Coefficient of Drag (CD) x Frontal Area (A)
Coefficient of Drag is determined by the shape of the object and describes the drag or resistance in air flow. Frontal Area is the area of that object presented to the flow.
By decreasing the drag, Michael can increase his speed at the same power output or he can achieve the same speed by putting out less power. With this in mind, drag savings can be thought about in terms of ‘Watts saved’ to help athletes better understand the impact of the drag reduction. We’ll often report the savings in terms of a percentage difference, also.
The CDA recorded will be different for the athlete and setup at different speeds and wind directions, which is why we test and repeat runs across a matrix of different conditions. Ultimately, we’re looking for the best-performing equipment across a range of those conditions, not just a small number of data points.
Out on the roads in races, the air conditions and the pacing of the athlete are going to vary throughout, so testing across those conditions helps to inform what will perform best across the whole race. Our test protocol and data reporting also applies a weighting to the yaw angles, applying proportionally more ‘weight’ to the yaw angles we expect to be experienced more frequently on the average time trial course.
For Michael, we tested at 40, 45 and 50kph and across yaw angles (wind direction) of 0, 3 and 8 degrees. Data was captured over a sample of 18 seconds whilst pedalling at a steady power.
Testing: the run plan
- Baseline – team skinsuit, own overshoes: once set up in the wind tunnel, Michael’s first runs were across his baseline setup, which included his team-issue skinsuit and calf-guards. The subsequent runs would then compare back to this baseline to establish the difference in CDA.
- Team skinsuit, Vorteq overshoes: keeping everything else the same, we switched Michael’s own overshoes for the Vorteq ones to find the resulting drag reduction. Between 40-50kph, switching to Vorteq overshoes resulted between 0.3% and 2.2% reduction in CDA. This is at the lower end of what we’ve typically seen but still a performance advantage over a good set of market-leading calf-guards.
- Vorteq skinsuit, Vorteq overshoes: having established that the Vorteq overshoes were faster, Michael kept these on for the remainder of the runs. The change to a Vorteq suit reduced drag by between 5.5% and 7.1%. At 45kph, the 7.1% drag reduction would translate to a saving of 23 Watts, which would estimate a time saving of 65.4 seconds over a 40km time trial.
As a summary from the clothing testing and after averaging across the different yaws and repeat runs, we had found between 5.8 and 8.5% for Michael from switching to Vorteq skinsuit and overshoes (the majority of this coming from the skinsuit).
With some extra time in the wind tunnel, we decided to explore some other changes in an attempt to optimise the setup and position around the new clothing. We reduced the number of speeds and yaw angles tested for the remaining runs to get through a sufficient number of changes and repeats.
Using Silverstone Sports Engineering Hub’s well-stocked kit room, we tried some alternative time trial helmets on Michael. Just like with the clothing, a helmet can perform differently at different conditions and shapes of rider, so we tested to see if we could find any more significant drag reduction by switching. Using our engineers’ knowledge of the likely effects of equipment changes on certain body shapes and positions, we were able to recommend an improved setup for the athlete.
Swapping from the baseline helmet to a different one found a 3% saving. Removing the gloves found nearly 1% (2.5W) drag reduction. There weren’t any further significant findings, but it was a productive session and successfully validated the performance of the custom-fit skinsuit and overshoes.
The take-home figure was the 5.8-8.5% saving from the new clothing, but at a particular point (3 degrees of yaw and 45kph), Michael was saving 39.9 Watts (11.5%) with his optimised setup. The estimated savings across a range of speed and yaw would be between 59-72 seconds.
If you have any questions about Vorteq or want to find out how we can help you find a guaranteed, measurable performance advantage, feel free to get in touch on info@vorteqsports.co.uk.