Estimation of Forces Acting on a Sailboat Using a Kinematic Sensor

Amateur keel boat racing has become increasingly popular in coastal regions with a long sailing tradition, such as the Adriatic. Although the traditional experience is transferred to new generations of skippers and crews that compete in national and international regattas with open class boats, the material limits of the boat are often measured subjectively, by sail or mast failure, and transferred through a story. Most sailors know why a component failed, but often they do not know what force was needed for the particular failure. Forces acting on a boat are usually estimated with CFD and towing tank experiment for relevant sailing conditions, but full scale data in seaway are rarely taken. Here we want to show a low budget method to get a rough estimate of aerodynamic and hydrodynamic forces acting on a keel sailboat using a kinematic sensor. Some approximations are taken into account to construct a simplified mathematical sailboat model, which allow to relate kinematic data to forces acting on the sail, hull, keel, and rudder. Some data such as the geometry and mass distribution of the boat has to be known; other parameters such as water resistance instead has to be experimentally measured. The results of a series of measurements are presented and discussed. Looking on the limitations of such a method, a proposal for a new sensor is made