Effects of Masts on the Aerodynamics of Sail Sections

Abstract

The effects of the addition of masts of varying geometries to two different sail-like two-dimensional airfoil sections were determined by water tunnel tests. Thirteen different mast-sail combinations were tested with four of the sections retested at a different time to confirm repeatability of the data. The results were found to be best presented and best understood by means of graphs of drag coefficient versus lift coefficient for fixed values of d/c(mast diameter/sail chord). The additional drag caused by the addition of a mast was found to be substantial, especially as the ratio d/cbecame relatively large. Results were found to be insensitive to changes in Reynolds number of a factor of two for d/cless than 0.3 for round masts, and 0.2 for elliptical masts (d for an elliptical mast is taken as the diameter of a circle having the same cross-sectional area). Elliptical masts with d/c greater than 0.3 gave results which exhibited a sensitivity to Reynolds number and which, over a limited range of lift coefficients, gave an unexpectedly high value of the ratio of lift coefficient/drag coefficient.