—Sailing experts can explain basic sailing skills by rules about how to steer sails and rudder according to direction of target and wind. This paper describes how to transform the sailor’s knowledge into Mamdani type fuzzy inference systems. The proposed system controls two actuators – rudder and sails – even during tack and jibe. In combination with an automatic weather routeing system the sailboat is able to reach any target completely autonomously. Experiments on a demonstration sailboat have shown excellent results. Detailed log data analysis shows manoeuvres carried out as expected by sailing experts.