FRICTIONAL RESISTANCE REDUCING DEVICE USING EXTERNAL AIR, AND STEPPED BOAT HAVING SAME

摘要

The present invention provides a frictional resistance reducing device using external air, and a stepped boat having same, the device having a simple structure and mixing external air with seawater so as to implement an air-seawater mixture having uniform microbubbles, and spraying same to the bottom of the boat. To this end, the frictional resistance reducing device (200) using external air, of the present invention, comprises: an external air inflow pipe (210); a seawater inflow pipe (220) formed at the side surface of a hull (100) of the boat; an air suction device (260); a compressed air chamber (212); an air discharge pipe (213) formed at the lower end of the compressed air chamber (212); a seawater discharge pipe (223) formed so as to communicate with the seawater inflow pipe (220) and one side surface of the air discharge pipe (213); an air-seawater mixture moving pipe (240); a mixing chamber (250) connected to the lower end of the air-seawater mixture moving pipe (240) in an eccentric state; and a spray port (251) formed so as to be connected to the mixing chamber (250) and the outside of the hull (100).