Experimental Strain Analysis of the Mast of a 420 Sailboat During Sailing

Aim of the work was the experimental strain analysis of a 420 sailboat mast during sailing: this type of data is of great interest in the structural design of sailboat masts and hulls as well as in the sail-making. The work involved the design, calibration and installation of strain gauge bridges at seven sections of an instrumented mast and at the shrouds: this was followed by the collection of strain data during simulated laboratory rigging tests and real sailing sessions with medium/strong wind. Compression loads at the mast step were recorded with a customised load cell calibrated on a force platform. On the basis of laboratory calibration constants, the strain measurements were converted into structural loads and averaged over steady states during rigging and sailing either close to the wind or beam reach: the longitudinal bending moment, the lateral bending moment and the axial loads were analysed and plotted along the 6.20 m mast length. Highest values of lateral bending (146 ± 14.5 Nm) were recorded at the mast head, whereas longitudinal bending showed highest values at the vang connection to the mast (229 ± 29 Nm). Tension loads acting on the shrouds were also measured with highest values of 2887 ± 167 N. The knowledge of loads acting along the mast will support the designers in improving the mast’s cross section profile, the material selection and the validation of numerical structural analysis. Moreover, experimental data about the loads acting on the standing rigging and on the mast-step during sailing will support the optimised design of the boat shell.