Investigating the position of manufacturers’ binding positions of alpine skis with similar shape and flexural rigidity

Abstract

The purpose of this study was to investigate the manufacturers’ binding positions of skis of similar shape and flexural rigidity. The shape of eight skis from five different manufacturers was characterized by six primary geometric variables. The skis were then subjected to a mechanical three‐point bend test, and the resulting deformation was measured using three high‐speed cameras. The Euler‐Bernoulli equation was used to calculate the distributed flexural rigidity (E[x]I[x]) from the shape of the deformed ski, where E is elasticity, I is inertia, and x is the longitudinal position along the ski's length. Two null hypotheses were tested: skis that are similar in shape will have similar binding positions, and skis that have similar flexural rigidities will have similar binding positions. The results of the study identified two different groups of skis that were nearly identical in geometry and whose patterns of flexural rigidity nearly coincided; however, the skis in each of the two groups had substantially different binding positions. The inconsistent binding position of skis that were otherwise similar in shape and in flexural rigidity manifests as a confounding variable in experimental studies. If ski shape and flexural rigidity are maintained as control variables, efforts need to be made to measure and control binding position, so as not to compromise the internal validity of the experimental design in alpine skiing research.