Method of forming air layer over immersed surfaces of structure having immersed portions, and structure of coat layer formed over immersed surfaces

A method of forming an air layer over an immersed surface of a structure having an immersed portion, comprising the steps of:

• covering the immersed surface of a structure having an immersed portion with a coating layer, which has minute depressions and projections at the surface thereof and which has at least vertices of the projections formed of a water-repellent material;
• and supplying air to the coating surface to form an air layer between the coating surface and water wherein said covering of the immersed surface comprises:
• providing a coating layer formed over the surface of a structure;
• and
• forming fine depressions and projections in the surface of the coating layer by fine particles;
• covering the fine particles with a water-repellent material.

A a method of forming an air layer over an immersed surface of a structure having an immersed portion, comprising the steps of:

• covering the immersed surface of a structure having an immersed portion with a coating layer, which has minute depressions and projections at the surface thereof and which has at least vertices of the projections formed of a water-repellent material;
• and supplying air to the coating surface to form an air layer between the coating surface and water, said coating layer having a two-layer, finely roughened structure formed by the steps comprising:
• providing a bottom layer formed on the surface of a structure and including relatively large particles;
• and
• providing a top layer formed on the bottom layer and including particles smaller than those of the bottom layer so that the two-layer, finely roughened structure has large depressions and projections and smaller depressions and projections formed on respective surfaces of layers.

A method of reducing the friction resistance between a marine vessel and water, comprising:

• making at least a water-contacting part of the marine vessel comprising a surface having a property of retaining air;
• providing an air injection zone at an upstream position on said surface;
• providing means for forming a thin layer of air over said surface of said water-contacting part with the air injected through said air injection zone when the marine vessel is navigated, forming said means by a coat layer having fine surface irregularities, and forming at least peak portions of the surface irregularities with a water repellent material;
• said coat layer retaining a primary air in water;
• supplying a secondary air out of said air injection zone into the primary air layer and permitting secondary air to be absorbed in and joined with the primary air layer and spread to form a thin layer of air over said surface;
• and
• navigating the marine vessel while a portion of air in a water contacting surface portion of the thin layer of air, to be carried away towards the stern of the marine vessel, is replenished with the secondary air injected through said air injection zone.

A marine vessel with a reduced friction resistance with water, comprising:

• a hull of which at least a water-contacting part comprises a surface having an air retaining property;
• an air injection zone provided at an upstream position on said surface;
• and
• means for forming a thin layer of air over said surface with the air injected through said air injection zone when the marine vessel is navigated, said means comprising a coat layer having fine surface irregularities, at least peak or top portions of said surface irregularities being formed of a water repellent material said coat layer having a property of retaining in water a primary air comprising a thin film of air;
• said air injection zone extending in the direction of the hull width in a manner such that at an upstream position on said coat layer, said air injection zone can inject a secondary air to the vicinity of the surface of the coat layer;
• the arrangement being such that the secondary air is supplied to the primary air retained over the surface of the coat layer and permitted to spread over the surface of the coat layer to form a thin layer of air, which is constantly maintained over the water-contacting part of the marine vessel with an amount of air to be peeled and carried away from a stern part of the marine vessel in accordance with the navigation of the marine vessel being replenished with the secondary air being supplied.