Amateur keel boat racing has becoming more and more popular on coastal regions with an old sailing tradition, such as in Adriatic. Although the traditional experience is transmitted to new generations of skippers and crews that compete on national and international regattas with open class boat, the material limits of the boat are often measured subjectively, by sail or mast failure, and transmitted by a story. Most sailors know why some component failed, but often they don’t 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 wanted 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 sail, hull, keel and rudder. Some data 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. 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.
A Towing-tank Experiment on Dynamics of Air Bubble Introducer for Drag Reduction of Ships - Flow Visualization of Air Entrainment and Bubble Formation by the Flow Past a Cylinder beneath a Free Surface -