A number of wind tunnel tests have been conducted by the Wolfson Unit in aid of the development of sailing rigs for both cruising and racing boats, including recent tests for the United States Sailing Association as part of the joint IMS/PHRF research programme. In the process of these tests developments have been made in both the test techniques and the analysis methods, which have enabled the components of drag to be identified for different sail settings. This paper describes the tests for evaluating the upwind rig performance of a sloop and compares the components of drag with those in the aerodynamic model used in the IMS VPP. The aerodynamic behaviour of the rig is described using plots of the variation of sail forces and moments with sail settings with the aim of helping sailors understand the effects of changing sail settings. It is shown that the wind tunnel data match closely the IMS aerodynamic model and that this model can be simply programmed by sailors and designers into a spreadsheet to enable the rig planform to be optimised for particular conditions. The results are compared with those obtained using a full VPP calculation.

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