### TW University

Hockey Stick Flex Profiles

Rod Cross, University of Sydney, Sydney, Australia
Crawford Lindsey, Tennis Warehouse, San Luis Obispo, CA
November 15, 2016

Note: See "Flex of a Hockey Stick" for an expanded discussion of the science of hockey stick flex.

#### Introduction

Some sticks are more flexible at the blade end, some are more flexible at the handle end, and some are more flexible in the middle. The flex rating of a stick is just the average flex over a 1.0 m long section in the middle. In order to measure the variation in flexibility along the shaft, the authors took a sample of 13 high performance sticks and bent them over five different 0.6 m long sections from one end to the other. Each section started 0.2 m from the next and overlapped the next section, as indicated in Fig. 1. A vertical force, F, was applied in the middle of each section, as indicated by the arrow, and the vertical deflection, y was measured in order to calculate the stiffness k = F/y of each section. The deflection, y, was only about 5 mm in this test since a deflection of one inch over each 0.6 m length could easily have broken the stick.

In theory, the flex over a 0.6 m long section of the shaft is 4.63 times larger than the flex over a 1.0 m long section, since the shaft stiffness is inversely proportional to the cube of the bending length. In order to compare the flex over each 0.6 m long section of the shaft with the flex over the 1.0 m long section, we divided the measured stiffness of the shorter sections by 4.63 to provide a meaningful comparison. That way, the flex of each short section could be compared directly with the average flex of the 1.0 m long middle section. The results are displayed below in the Flex Profile Gallery.