Physics: Javelin Designs, what’s the significance?
Blunt tip tail wind or sharp tip head wind; what’s the verdict?
There is often much dispute about which type of javelin tip or design gives the most benefit to the javelin throw. The two main designs are tail wind (blunt tip) and head wind (sharp tip), with another “all wind” design that closely resembles the head wind javelin. In this article we will discuss current evidence.
Science: Les Hatton from the Faculty of Computing, Information Systems and Mathematics at the University of Kingston published a paper titled “Optimising the javelin throw in the presence of prevailing winds” , which was updated on January 28, 2007. The mathematical model is based and calibrated on data from various championships’ results. It is a very sophisticated model, which “solves a coupled non-linear set of ordinary differential equations that incorporate the full three-dimensional effects of lift, drag and rotation” of the javelin throw. Using the Javelin Flight Analyser software based on this model, the following results provide an idea of the effect of javelin design on distance.
Table 1. Wind Direction
|Wind Direction (°)||Distance (m)|
|0 = Head wind||56.87||64.00||65.3||66.66|
|45 = Right Head||58.87||66.1||67.38||68.17|
|90 = Right Cross||63.9||71.21||72.4||73.62|
|135 = Right Tail||69.15||76.33||77.4||78.47|
|180 = Tail wind||71.39||78.46||79.46||80.48|
|225 = Left Tail||69.12||76.3||77.36||78.44|
|270 = Left Cross||63.82||71.1||72.3||73.51|
|315 = Left Head||58.84||66.06||67.34||68.66|
|Attack Angle (°)||0||-5||0||5|
|Release Angle (°)||30||40||40||40|
|Constant: Javelin = Tailwind, Weight = 800g, Wind Speed = 2.0 m/s, Release Velocity = 26 m/s|
Conclusion: From the table above you can see that a tailwind or blunt tip is slightly beneficial is all wind conditions. Of course there are limitations to this model as described by Hatton in his paper, and no data exists on the “all wind” javelins.
There is some speculation on whether the blunt tip of the tail wind javelin creates a pressure behind the tip of the javelin much like a aeroplane wing. I.e. instead of the air flowing along the javelin tip such as in a sharp tipped head wind javelin, the air is pushed out away from the tip by the blunt tip, reducing the drag just behind the tip of the javelin. We will update on the aerodynamics of this speculation after consultation with an aerodynamics engineer or specialist.
References:1. Hatton, Les. Optimising the javelin throw in the presence of prevailing winds. University of Kingston, January 28, 2007. http://www.leshatton.org/javelin_2005.html [Accessed 10 November 2010].