AeroLab Tech

A great few days at the riding, racing, product testing, and spreading the love of aero!
R&D engineer competed in the B category of the circuit and road race with the primary take away of how fast the Californians are!
A few key take always from Matt’s tactics and analysis related to the importance of positioning and aerodynamics soon to follow!

Wait? Isn’t drafting illegal?
In the Figure above we have plotted how much power you can save while riding ‘in the draft’ of a lead rider for various wind yaw angles. The vertical red lines show the legal limits for bike spacing within World Triathlon and Challenge events. You may wonder “why does wind yaw matter?”: Although crosswinds cause portions of the first rider’s wake to be redirected off-course (reducing draft effects), even at modest yaw angles it is possible to benefit from ‘drafting’. In the plot below at a 12 meter `drafting` distance and moderate wind conditions a rider can experience a reduction of 10 to 40 Watts (5 to 18%) to maintain the lead rider’s speed (44 kph in this example). In contrast, at a 20 meter distance the reduction is less but still significant at up to 15 Watts.
So what does this mean for you? If you can swim like a fish just hold a second while we catch up. For the rest of us, it is possible that burning a few matches on the swim to stay with a strong group can pay dividends in power savings on the bike even at legal ‘drafting’ distances 😉

This week we wanted to talk about something all cyclists and triathletes think about, weight. As most athletes are now heading into the off-season it’s time to look forward to holiday dinners and the occasional extra beer! It’s normal, if not beneficial, for an athlete to put on a little extra weight as we wind down our training volume in preparation for the next cycle! We wanted to put it in perspective how adding up to 2kg compares to any equivalent decrease in the magnitude of CdA.
Using the same example rider from our previous post we assumed an input power of 250 watts to calculate our steady state speeds. In the first slide we have iso-contours of the additional power required to maintain speed for the added mass (y-axis) vs road gradient (x-axis) if CdA is constant. In the second slide we the same figure except solved for for the amount needed to decrease CdA in order to maintain the same speed.
The most important difference between the two figures is the shaped of the contour lines and how quickly the colour changes. What we mean by this is in the power map (slide 1) it is clear that an athlete would have to increase their power as the grade increase with additional weight, news to no one. However, in the CdA map (slide 2) there is much more blue and a more gradual change in the required CdA decrease. This shows that even modest improvements in CdA can account for fluctuations in weight as until the road is very steep.
All in all, we wanted to show the relative importance of weight and CdA and how even up to 2kg is only a 6 watt increase! As long as we don’t go crazy in the off-season that weight will come off come race day and any improvement in CdA will just be gravy 😉