There are three major components that make up the resistance forces on a sailing yacht: 1) Viscous resistance, which includes friction resistance between the hull and water and viscous pressure resistance based on the hull shape; 2) Wave resistance, which is generated as the yacht displaces and deflects water, forming waves that take energy from the yacht's movement; 3) Additional resistance, including aerodynamic resistance of the sails and hydrodynamic resistance of components like the rudder and centerboard.

1. Sailing Yacht’s Hull Design

2. Index: Forces and moments on a sailing yacht Resistance components: Viscous resistance: The Friction resistance The viscous pressure resistance Wave resistance. Additional resistance.

3. Forces and moments on a sailing yacht

4. Resistance components: There are three major components: Viscous resistance Wave resistance Additional resistance

5. The Viscous resistance *Due to the frictional forces between the hull and the water *The viscosity gives rise to this component. *Boundary layer is the water close to the hull that moves with it.

6. The Friction resistance *Directly due to the friction between the water and the hull surface. *Based on the Reynolds number Rn=V*L/v Rv=1/2*p*Aw*V*Cv *The wetted area gives rise to this component

7. The viscous pressure resistance *Based on the Bernouilli’s ecuation that relates the velocity of the flow with it’s pressure. *The bow and stern pressures are higher than in the middle part of the hull. *It depends basically on the shape of the hull

8. Wave resistance. *The second major resistance component *When a yacht sails through the water, deflects a volume of water. *This one generates two trains of waves. *The wave formation takes energy from the movement of the yacht. *Based on the Froude number: Fn=V/(g*L)1/2

9. Additional resistance. *Due to the aerodynamic resistance *Due to the roughness Due to the hydrodynamic resistance of HEEL, PROPELLER, RUDDER and LEEBOARD

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