Performance Prediction for Sailing Dinghies Prof Alexander H Day Department of Naval Architecture, Ocean and Marine Engineering University of Strathclyde Henry Dyer Building 100 Montrose St Glasgow G4 0LZ
[email protected] 2nd Revision Feb 2017 Abstract This study describes the development of an approach for performance prediction for a sailing dinghy. Key modelling issues addressed include sail depowering for sailing dinghies which cannot reef; effect of crew physique on sailing performance, components of hydrodynamic and aerodynamic drag, decoupling of heel angle from heeling moment, and the importance of yaw moment equilibrium. In order to illustrate the approaches described, a customised velocity prediction program (VPP) is developed for a Laser dinghy. Results show excellent agreement with measured data for upwind sailing, and correctly predict some phenomena observed in practice. Some discrepancies are found in downwind conditions, but it is speculated that this may be related at least in part to the sailing conditions in which the measured data was gathered. The effect of crew weight is studied by comparing time deltas for crews of different physique relative to a baseline 80kg sailor. Results show relatively high sensitivity of the performance around a race course to the weight of the crew, with a 10kg change contributing to time deltas of more than 60 seconds relative to the baseline sailor over a race of one hour duration at the extremes of the wind speed range examined. Keywords sailing; dinghy; velocity prediction program; performance modelling Performance Prediction for Sailing Dinghies 1 Introduction 1.1 Velocity Prediction Programs Velocity Prediction Programs (VPPs) for sailing yachts were first developed more than thirty-five years ago (Kerwin (1978)) and a wide variety of commercial software is available.