Schooner Brilliant Sail Coefficients and Speed Polars

The sail coefficients for a schooner rig, as a function of wind angle and heel angle, are presented, based on an experimental program, for historic vessel research, at Mystic Seaport, using the 61'6" schooner Brilliant. The coefficients were determined by full-scale sailing tests and 9- scale model tow-tank tests. Sail coefficients CR and Cttare defined as the drive force and horizontal side force , due to the sails, rigging, and hull above the waterline, per unit of sail area, per unit of wind pressure. These coefficients can be used to study performance of historic schooner­rigged vessels, predict performance of new designs, and compare performance of schooners and sloops. Sail coefficients for sloops have long been available. A velocity prediction program for the schooner was also developed. The predicted and actual ship speeds agree, with standard deviation of0.028 in the ratio. Upwind sail coefficients for the schooner are found to be lower than for historic sloops, and display the expected droop with heel. The schooner velocity made good upwind is largest with the sail plan of four lowers plus fisherman staysail. The schooner and sloop both point higher as wind increases. The sloop outpoints the schooner at all wind speeds, by about 10°. On a beam reach or broad reach, schooner speed is largest with the sail plan of big jib, golliwobbler, and mainsail. This sail plan also produces the largest downwind velocity made good. The polars suggest that the schooner has the advantage over the sloop on a beam reach.