The measurement of unsteady sailor loadings for single-handed olympic sailboats

Abstract

The performance analysis of Olympic sailor’s has typically been based on race outcomes, two boat testing, and formative feedback from athletes and coaches. Sailors body-motions are thought to be a key factor in the up-wind performance of a sailor. However, despite the focus of a large portion of sailing literature on improving body-motions, and international rules restricting the use of them in competition, no methods have been formulated to predict the performance impact of these motions, or to measure the unsteady loadings they exert on the sailboat.
A sailing-specific pose-capture method to estimate sailor loadings was developed and evaluated. StickMan uses a network of seven wireless inertial-magnetic motion trackers to measure a sailor’s hiking pose and boat orientation. A human mass distribution model was used to estimate body-segment mass properties to derive the external loads sailors exert on their boat. Hiking (roll) moment estimates were evaluated for accuracy using an instrumented motion platform under sinusoidal roll motion for sequences of static and dynamic hiking poses. Hiking moments estimated using pose-capture had an average 10.0% overestimate under dynamic conditions. The estimate had excellent transient and tracked reference measurements even under explosively dynamic hiking motion spanning 1000 Nm.
A global sensitivity analysis was performed on hiking moment estimates. The uncertainty for hiking poses was 712 ± 38 Nm (5.3%) which the human mass distribution model contributed up to 70 % towards. Instrumentation uncertainty, including orientation drift, was not significant for hiking poses over 8 knots of wind.
A case-study was performed to demonstrate the use of the method applied to the performance analysis of roll tacks and upwind hiking moment to make initial assessments of the performance implications of a sailor’s ability to perform roll tacks. GPS positions and wind sensors were used to build a simple model of how a sailor-controlled hiking moment can a↵ect boat speed. This shows the method was suitable for analysing dynamic hiking methods in terms of boat performance.

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ORCID for Dominic Hudson: orcid.org/0000-0002-2012-6255

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