Prior research has shown piezoelectric vibration sensors can detect sail luffing, the acceleration of a flexible sail out of its normal wing state caused by a momentary reversal of the air pressure gradient over the sail. Luffing decreases boat performance by reducing the lift generated by the sail. Yet detecting sail luffing in flexible sails for robotic sailboats is still challenging. This paper presents three methods of sensing characteristics of a luff – air pressure differential which causes the luff, the acceleration of the sail as the luff occurs, and the influence of motion and acceleration of a luffing sail on members placed on the sail. We assess three different sensor types based on cost, ease of use, complexity of electrical interface, power consumption, accuracy of the sensor and amount of noise in sensor readings. To classify the most effective sensor for a given set of constraints, a multifaceted analysis has been performed with a piezoelectric vibration sensor, an acceleration sensor, and a gas pressure sensor. The accuracy and precision of each sensor at sensing sail luffing is evaluated by comparing the sensor output with a plot of the position of a single point on the sail through time generated with computer vision.