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frequently encountered. No particular skill or operating procedure 

 is required except a good degree of common sense if these pieces of 

 brash ice become heavy enough to throw the icebreaker off her course. 



In open pack, where numerous big open leads are to be found, the 

 progress of the ship will be determined by the conning officer's skill in 

 spotting the best leads far enough ahead to keep his ship on the course 

 nearest to the base course desired. Practically any speed desired may 

 be used, provided caution is used in maneuvering around and between 

 heavy floes in order not to strike the bow into these floes so as to cause 

 the ship to be thrown off her course, possibly to such an extent that 

 she will hit and rebound from floes on the other side. An experienced 

 helmsman can maneuver the ship through this type of ice if the officer 

 of the deck will merely point out to him which direction or lead to 

 take and then let the helmsman use his own initiative. The passage 

 of an icebreaker through this type of ice can be compared to an auto- 

 mobile driving through heavy traffic. The chauffeur can do better if 

 back seat drivers are kept to a minimum. 



In close pack or field ice the icebreaker literally runs into the real job 

 of ice breaking. It is very serious business and must be approached 

 with the highest degree of skill possible. First the ship should be 

 ballasted properly, down as much as the ballast and trim tanks will 

 permit, not only to protect the propeller but also to keep the engine 

 injections low enough to avoid their being clogged with broken ice. 



The bow should ride lower than the stern in order to present a sharp 

 cutting edge for entering the ice. Because the center of gravity is 

 moved forward under these ballasting conditions, more weight is 

 concentrated forward to wedge the ship through the ice. As the bow 

 comes up onto the ice, the ship's more buoyant stern is forced down ; 

 however, this extra buoyancy causes the stern to be pushed up again 

 until it regains equilibrium with the bow. In effect, as the bow is lifted 

 by the ice there is a constant lifting under the stern tending to force the 

 bow back down again. The weight of the bow, of course, is what 

 breaks the ice. Another advantage of keeping the bow low is that the 

 ice is broken and forced out along the sides of the ship where it will 

 slide clear of the screws and rudder. It has been observed that where 

 extremely heavy floes were run upon by a high bow and low stern, if 

 there was not ample room for a floe to slide to one side due to the heavy 

 pack, then the floe would slide under the hull and come up aft in the way 

 of the propellers. However, the bow should not be trimmed down to 

 the extent where the screws are raised appreciably, further endangering 

 them. 



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