Yes, that is why the dynamometer is attached and the attachment is such that the force is horizontal and axial, there is no transverse force therefore, there is no roll sway or yaw, the model is constrained against roll sway and yaw, it can only heave and trim. And you must have measuring devices to measure the resistance, the force, the heaving and the trimming, the other thing that must be measured is the speed. So, the carriage is the one that provides the speed, constant speed.