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moderate breeze, and drift into the ice, thereby endangering the rudder 

 and propeller. 



On impact with ice, the ship will move in the direction of least resist- 

 ance without regard to the position of the rudder. With experience, a 

 helmsman may be able to take advantage of this fact. 



A twin-screw vessel is at a distinct disadvantage in ice navigation 

 because of vulnerability of her propellers, although twin screws give 

 much greater maneuverability. One successful expedient that has 

 been adopted by such vessels to minimize propeller damage when in ice 

 is to set a propeller watch. A man is stationed on each side of the 

 f antail directly over the propeller guard, with phone communication to 

 the bridge. He is instructed to report ice in contact with the side of the 

 ship especially if the thickness extends to the upper side of the propeller 

 blades. When such pieces have reached a point 30 feet forward of his 

 position, the report "starboard (or port) foul" is made to the bridge, 

 and the screw concerned is stopped until the report "starboard (or 

 port) clear" is received. The U. S. S. Edisto found a preferable 



Figure 18. — U. S. S. Edisto in drydock. Port propeller and externol portion of shaft were 

 sheared off due to contact with the hard ice of the Lincoln Sea. Shaft is 1 8 inches in diameter. 



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