design of the bulb, from a long knife-type form, to a ball-form. The ideal situation is one where the ship cuts through the waves, generating no waves itself. Every wave that is created by the ship is energy wasted: compare a tugboat e with a fine yacht. s The bulb is most effective at a certain draught, for loaded or ballast condition. It could well be that in the case of the adverse situation a bulb produces more resistance (see also chapter propulsion)