Engineering in Sports: Javelin Throwing

Due to the massive distances men (Uwe Hohn in particular) were throwing javelins in 1984 (over 100m), there was a danger that a javelin would clear the throwing area. To reduce the javelin's flight time it was redesigned to put its center of gravity in front of its center of pressure, so its nose pitched downwards in flight. This is an unusual example of a sport's governing body using engineering to justify a rule change, in contrast to the more usual rule change in response to an engineering innovation by a competitor.

The new javelins succeeded in reducing distances by about 10%. However, applying basic fluid dynamics, javelin manufacturers were able to recoup some of the lost distance by increasing the javelin's tail drag by roughening the tail's surface (using holes or dimples). This modification pulled the center of pressure back toward the center of gravity, improving the javelin's flight characteristics.

In an international javelin competition a selection of sanctioned javelins is available for competitors to use; personal javelins are banned. This means that each competitor has access to the latest and greatest equipment, thus leveling the playing field (excuse the pun) for all.

In 1991 javelin tail roughening was banned and all records achieved with such javelins were nullified. Of course distances have crept towards 100m again, with the current record being held by Jan Zelezny at 98.48m.


I think we like to assume that the only difference between sports competitors is the human element, whether it is a racecar driver, cyclist, javelin thrower or swimmer. This is true for some sports (e.g., running) more than others (e.g., yachting). Still it would be a shame if relatively simple sporting contests, such as swimming, become a financial arms race with the rewards going to the better funded competitor. In the ideal world, engineering developments would be inexpensively available to all competitors (as in a javelin competition), thus advancing the sport and ensuring the best athlete wins - surely the ideal of most sports.


Javelin Rule Change

FYI The javelin rule change was primarily enacted to get the javelins to land not so flat but at a steeper angle so the judging of the throws exact landing point would be easier. The aerodynamics of the javelin had been brought to such a high level that the javelins were holding a nose up gliding angle of attack until the very end of their flight cycle. Sometimes they wouldn't turn over in time, and judging this was problematic. Mostly this was for the Held Custom lll javelin, thrown by Hohn and the previous world record holder, Tom Petranoff.
The big distances were a consideration too but it was the difficulty in marking the throws that got the rule change going. It was so successful (though the javelins were much less fun to throw!) that the rules were also changed for the women's javelin a few years later, creating more easily marked, steeper landing angles.

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