Effect of polymer-composite coating on the strength and stiffness of a freestanding wooden mast of a sailing yacht

The design, modeling and calculation of strength and stiffness of a free-standing wooden mast of a sailing yacht carrying a Chinese sail are considered. The peculiarity of freestanding masts is that they are fixed by their lower part in the hull of the yacht and there is no standing rigging. In this paper we have designed free-standing fore- and mainmasts for a yacht under construction with "Chinese junk" type sailing armament. The masts have a pine lath glued hollow-body construction with a circular cross-section. The masts are cylindrical in the below-deck part and conical in the above-deck part. The spurs and top of the masts, as well as the areas near the mast hole have a continuous crosssection. Diameters, thickness of mast walls, greatest displacements and stresses are determined from the solution of the beam theory equation with some simplifications of mast construction and external load from sails. The verification calculations are performed by the finite element method with 1D- and 3D-modeling of the masts. The analysis of the influence on the stiffness and strength of the masts of gluing their outer surface with polymer composite material based on carbon fiber is carried out. Expressions for the reduced modulus of elasticity and stresses for beam models of glued masts, as well as the value of the equivalent modulus of elasticity of polymer-composite coating for 3D-models of masts are obtained. Comparative calculations have been performed for the mainsail mast using the three calculation models described above. It is shown that polymer composite coating the mast with a total thickness of 1 mm allows increasing its strength and rigidity, reducing the cross-sectional dimensions and reducing the mast weight by 17%.