# The Impact of Skinsuit Zigzag Tape Turbulators on Speed Skating Performance
## 3 Measurements
### Static Skater Measurements
#### 3.3.2 Results  
Figure 8 presents the measured drag area of a male long-distance skater for three configurations: the impact of 0.5 mm thick Teflon zigzag tape (also depicted in Figure 5) on the lower legs and of 0.75 mm thick zigzag tape on the cap. The averages over the five runs are tabulated in Table 1.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Configuration** & **C\({}_{\mathbf{D}}\)A** & **\(\sigma\) (\%)** \\ \hline Standard suit, no tape, series 1 & 0.255 & 0.7 \\ Standard suit, zigzag tape on lower legs & 0.233 & 1.9 \\ Standard suit, no tape, series 2 & 0.255 & 1.7 \\ Standard suit, zigzag tape on cap & 0.244 & 8.1 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Averages over five runs of the drag area C\({}_{\mathbf{D}}\)A of three configurations showing the effect of 0.5 mm thick zigzag tape on lower legs and 0.75 mm on the cap.  
Figure 7: The test setup of the measurements on live skaters in January 1997.  
Looking at the standard deviation, \(\sigma\), shown in Table 1, we see that the followed procedure gives reasonably steady results for the conditions with no tape on the cap. The race suit used for the tests was made of Coolmax, a polyester fabric, following the trend of those days, which was to use increasingly smooth breathable fabrics. The values in Table 1 indicate an average reduction of the total drag of the skater due to the zigzag tape on the lower legs of 8.6%. With a frontal area of the lower legs of about 20% of the total for this particular skater, this means a drag reduction of the lower legs of roughly 40%, which is 20% per leg. It must be noted that the turbulence intensity of the open jet wind tunnel was in the order of 0.8%. Increased small-scale turbulence promotes boundary layer transition, which, in this case, might have led to a reduction in drag for the smooth suit already, compared to a situation with relatively low turbulence, such as the case of an isolated skater on an indoor skating Fink. Furthermore, the tape was at an azimuth position of 55 degrees, which, in combination with the 0.5 mm thick tape (on the thin side according to Figure 5), may not have led to a maximum drag reduction.  
Despite the right starting position, there is a large variation in the drag area of the configuration with zigzag tape on the cap only. Without any other known explanation (during these very first tests, changes in posture were not constantly recorded by a camera), this might be due to the fact that the drag of the head is actually reduced, which may feel (and perhaps also sound) unfamiliar to the skater and may have led to variation of the position of the head or even the trunk during the runs. The impact of the tape on the cap of this particular skater is rather inconclusive, given the large spread in the data. Based on the averages, the application of the zigzag tape on the cap led to a total drag reduction of 4.3%. Tests on a female skater with zigzag tape on the cap, in the same test campaign, gave a reduction of up to 2.8% on overall drag (\(\sigma=0.9\%\)). Later measurements have shown that zigzag tape on the cap indeed can have a significant effect on the total drag, as it results in attached flow over a larger part of the head, which may have a strong positive influence on the flow over the back. Wind-tunnel tests in 2004 (in a different facility) revealed that the drag of a male skater wearing the Nike 2002 Olympic suit could be reduced with a  
Figure 8: The effect of zigzag tape on the lower legs and cap of a male long-distance speed skater’s drag area at a wind speed of 12.1 m/s. R\({}_{\rm D}\) = 0.8 \(\times\) 10\({}^{5}\) (based on lower-leg average equivalent diameter). Tape at 55\({}^{\circ}\) equivalent azimuth angle for five sequential test runs.  
little over 3% (\(\sigma\) = 0.6%) by applying zigzag tape with the right thickness and position on the cap. At present, it seems that skinsuit manufacturers underestimate the possible contribution of improving the flow over the head to lower drag.