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The major drawback of vessels of this design in ice is their inability 

 to withstand lateral ice pressure if they happen to become beset or are 

 deliberately frozen in. Although the whalers successfully wintered 

 in the Arctic by allowing their ships to freeze in at a location well 

 sheltered from the open sea, a long list of ships lost through ice pres- 

 sure when frozen in or ''nipped" could be compiled. DeLongs' Jean- 

 nette and Stefansson's Karliik in the Arctic and Shackleton's 

 Endurance in the Antarctic would be included. 



As a means of circumventing this disastrous possibility, a few ships 

 were designed with flaring sides and easy bilges so that there would 

 be no vertical surface for ice to bear against. The horizontal pressure 

 of the ice would thus have a lifting rather than a crushing effect. 

 Nansen's Fram^ built according to these principles, proved successful. 

 The design was further perfected by Christian Jensen in 191T in 

 Amundsen's Maud^ which spent several winters frozen in Arctic pack 

 and successfully negotiated the Northeast Passage. The Maud was a 

 wooden vessel of 392 gross tons, measuring 107.1 x 41 x 15.9 feet. She 

 was built with double layers of planking and diagonal bracing in the 

 hold, and had a 240-horsepower oil engine in addition to three-masted 

 schooner rig. 



ICEBREAKERS 



With the development of powered vessels came the possibility of 

 designing a vessel to cut or break through ice. Specially strength- 

 ened tugs or ferries were being used for this kind of work in harbors, 

 both in the United States and abroad, shortly after the steamboat 

 was introduced. In 1899 there appeared the first seagoing icebreaker, 

 the Ermack^ built in England for the Russian Government. Built of 

 steel, with \y^ inch plating along the waterline, this vessel displaced 

 10,000 tons and had engines of over 10,000 horsepower with three 

 screws aft and one forward. Although without precedent, her design 

 proved successful for her intended employment, and she may be re- 

 garded as the prototype of all later seagoing icebreakers. 



The Wind class icebreakers of the United States Navy and Ck)ast 

 Guard, described in the paper by Rear Adm. H. F. Johnson, represent 

 the latest development in United States seagoing icebreaker design. 

 With over-all dimensions of 269-foot length and 63-foot beam, they 

 displace 5.040 tons on 25 feet 9 inch draft. As originally designed they 

 were powered with six 2,000-liorsepower Diesel generator sets con- 

 nected to motors on the shafts. The electrical arrangements permitted 

 production of 5,000 horsepower on each of the two after shafts, or 

 3,300 horsepower each on all three. The bow propeller has been found 



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