A CFD-based model has been developed for predicting the aerodynamic forces on the rig and sails of the U.S. Brig Niagara. Wind tunnel tests and full-scale experiments were performed to validate the model. The model was then used to predict both the optimum sail trim for various points of sail, as well as the heel angle for different wind speeds. The results show that the optimum bracing (or trim) angle for square sails when sailing off the wind differs significantly from conventional wisdom. The stability analysis shows that the maximum heeling moment occurs when the apparent wind is approximately 80° from the bow, and that with a typical heavy weather sail configuration Niagara would be at risk of capsize in about 40 knots of wind. These results are useful for learning about square rig sailing as well as providing guidance to the Niagara’s officers regarding survivability of the ship.

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