Patent ID: 8689713

Claim:
A method of providing a watercraft with improved ice penetration characteristics, which watercraft has a hull with a first end and a second end and which is equipped at said second end with a propulsion arrangement which provides both the main propulsive thrust of the watercraft while the watercraft moves with either end ahead and the steering of the watercraft, wherein said second end of the hull is shaped and designed so that it has efficient ice penetration characteristics in that the watercraft has a design waterline and the second end of the hull is oblique in the vicinity of the design waterline and somewhat above it, said propulsion arrangement includes at least three propulsion devices each provided with a propeller, at least a majority of the propulsion devices are rudder propeller devices, and the propeller of at least one of the propulsion devices is at a first distance from the second end of the hull and the propeller of at least another one of the propulsion devices is at a second distance, greater than the first distance, from the second end of the hull, so that that when the watercraft moves in ice or ice build-ups with said second end ahead, at least one propeller at said first distance from said second end of the hull breaks ice and at least one propeller at said second distance from said second end of the hull moves disintegrated ice or ice chunks away from the ice build-up.