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Published on March 31st, 2013 | by Daniel

Cal Poly Study Reveals the Beauty of Nature’s Aerodynamic Designs

Jerald Testing

Photo credit: Kaori Photo

With bike companies looking for any aero advantage available, new research into cycling aerodynamics is increasingly turning conventional wisdom on its head. Kamm tail aero shapes found on Cervelo’s new Rca, the Trek Speed Concept, and the Scott Foil demonstrate that when it comes to aerodynamics, looks can be deceiving.

California Polytechnic State University (Cal Poly) in our hometown of San Luis Obispo, California has just released a new aerodynamic study that is likely to create a revolution in the cycling world. While investigating low-speed boundary layer aerodynamics, cyclists in the graduate aerospace engineering program asked the question, “Are shaved bodies more aerodynamic than hairy ones?” According to the study, the short answer is, “no.” But the long answer is a bit more complicated and highly nuanced.

When it comes to body hair and aerodynamics, it is not a case of ‘if some is good, then more is better.’ The study showed an optimal length of 16mm with an improved aerodynamic efficiency range of 15-25 watts depending on the size of the rider. However, at hair length exceeding 22mm, wind tunnel data revealed drag increases at an exponential rate. Hair shorter than 7mm offered significantly lower efficiency improvements.

Hair Drag GraphThe aerodynamic benefits of hair are the result of a principle called the “Stokes Boundary Layer Effect.” In a nutshell, the Stokes principle posits that a thin layer of turbulent gas or fluid on the surface of a body passing through it will serve to smooth the flow of gas or fluid thereby generating laminar flow. This is the principle behind the patented dimpling found on Zipp’s rims and Louis Garneua’s Vorttice helmet. Mother nature appeared to have this principle in mind as fast moving sea mammals evolved with an optimized hair length and orientation. Humans are no exception.

Jerald Aero Study

Photo credit: Kaori Photo

Recent Cal Poly graduate and Art’s Cyclery employee Jerald Westendorf served as one of the participants in the wind tunnel component of the study. Jerald tested a number of different hair lengths and remarked that his experience out on the road with the aid of a power meter and GPS supported the study’s conclusions. Jerald is also involved in a second study underway in the Cal Poly Kinesiology Department testing the thermal efficiency and wicking benefits offered by hair. While this study is far from finished, initial findings are promising.

Will we see bearded riders in the grand tours this year? Only time will tell. Getting riders to reject the sport’s traditional shaved leg aesthetic will certainly be an uphill battle for team managers. If it does happen, it represents a coup for recumbent riders across the world that have long shunned convention, cherishing their hair in the quest for ultimate efficiency.

Recumbents and Beards

Recumbents and beards go together like bread and butter.

Happy April Fools Everybody!

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About the Author

Daniel

Slusser is a professional bicycle mechanic with over ten years of experience. He holds a bachelor’s degree in business administration from HSU and a master’s degree in history from Cal Poly. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.



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