Sailing Yacht’s Hull Sailing Yacht’s Hull DesignDesign

Index:Index:

►Forces and moments on a sailing yachtForces and moments on a sailing yacht

►Resistance components:Resistance components:

Viscous resistance:Viscous resistance:►The Friction resistanceThe Friction resistance►The viscous pressure resistanceThe viscous pressure resistance

Wave resistance.Wave resistance. Additional resistance.Additional resistance.

Forces and moments on a Forces and moments on a sailing yachtsailing yacht

Resistance components:

►There are three major components:There are three major components:

Viscous resistanceViscous resistance

Wave resistanceWave resistance

Additional resistanceAdditional resistance

The Viscous resistanceThe 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.

The Friction resistanceThe 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

The viscous pressure The viscous pressure resistanceresistance

*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

Wave resistance.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

Additional resistance.Additional resistance.

*Due to the aerodynamic resistance

*Due to the roughness

Due to the hydrodynamic resistance of HEEL, PROPELLER, RUDDER and LEEBOARD

THE ENDTHE END