TQC Ship Propeller Roughness Comparators to the estimate the surface roughness by both touch and sight. The TQC Ship Propeller Roughness Comparators are developed for the specific profiles related to the condition of ships propellers over the life of the propeller.The TQC Ship Propeller Roughness Comparators are available in two models. Model LD2041 is the superintendent’s version for use in drydock or office.