Abstract: A disk has imprinted around its outer periphery various sailboat trim conditions, from beat to run. In the central portion of the disk is an index in the shape of a boat hull. Between this index and the outer periphery of the disk in a rotatable annular index with arrows for indicating the wind direction. By maintaining the central index in alignment with the longitudinal axis of the sailboat hull and rotating the annular index so that it is aligned with the wind direction, one obtains from the outer periphery of the disk a reading which indicates the proper trim of the sailboat for that wind direction.