Rudder

A rudder assembly to be arranged on a side of first and second propellers provided at a stern of a vessel at a distance in a right-left direction from each other and aligned at a same front-back position, the rudder assembly comprising:

• a first rudder unit to be arranged on both sides of the first propeller;
• and
• a second rudder unit to be arranged on both sides of the second propeller,
• wherein the first rudder unit includes, as seen from rear, a left rudder to be arranged on a left of the first propeller and a right rudder to be arranged on a right of the first propeller,
• wherein the second rudder unit includes, as seen from rear, a left rudder to be arranged on a left of the second propeller and a right rudder to be arranged on a right of the second propeller,
• wherein each left rudder of the first and second rudder units includes, as seen from rear, a first left rudder portion extending in the right-left direction, a second left rudder portion curved from a left end of the first left rudder portion toward lower left, and a third left rudder portion extending downwards from a lower end of the second left rudder portion, and
• each right rudder of the first and second rudder units comprising, as seen from rear, a first right rudder portion extending in the right-left direction, a second right rudder portion curved from a right end of the first right rudder portion toward lower right, and a third right rudder portion extending downwards from a lower end of the second right rudder portion,
• wherein, as seen from rear, lower surface of the first left rudder portion and the first right rudder portion of the first rudder unit are arranged at positions spaced upwardly apart from an upper edge of a tip circle line of the first propeller for a distance of 10 to 20% of a diameter of the first propeller, and
• wherein, as seen from rear, lower surfaces of the first left rudder portion and the first right rudder portion of the second rudder unit are arranged at positions spaced upwardly apart from an upper edge of a tip circle line of the second propeller for a distance of 10 to 20% of a diameter of the second propeller.