A BIOMECHANICAL ANALYSIS OF THE ESKIMO ROLL IN KAYAKING

Abstract

The purpose of the present study was to develop a mechanical model of the Eskimo roll in kayaking, in order to eventually develop an Eskimo roll simulator. The Eskimo roll is a very difficult skill to master, as the starting position is a stable position upside down in the water. A land-based simulator would assist the teaching and learning of this skill in a safe environment, but accurate simulation of the skill is difficult. Several trials of the Eskimo roll were filmed while being performed in an indoor pool; using four different camera views. Two cameras were Gen-locked together to film the sagittal and frontal views of the skill from the pool deck. One underwater camera filmed the skill from underneath the kayak, and one overhead camera filmed the skill from the top of the three-meter diving board. This film data was used to input actual values into an equation developed to determine the torques required to right the kayak. A computer program was written to produce the torques from the equation, with estimates for each of the terms. The Eskimo roll was modelled as an irregular cylinder, rotating around the longitudinal axis of the system consisting of the kayak plus kayaker. The kayaker used the paddle to apply torques to the water, to overcome his inertia and move the kayak to the upright position. The inertia of the kayak was due to the mass of the kayak, the mass of the kayaker, the drag force of the water against the system, and the torque due to gravity which had to be overcome during the righting movements. The righting torques were due to the lift forces and drag forces applied by the kayaker, as well as the buoyant force of the water as rotation began. These torques had to be estimated from film data, and from tabled values of moment of inertia, drag, and lift. The peak torques due to lift were estimated to be 150 N.m, while the peak torques due to drag forces were found to be 300 N.m. These estimates will be used to assist in the development of an on-land simulator which can be rolled only by application of torques of this approximate magnitude and direction.