Popular Science Monthly 



885 



Francisco for less than $29,000. Her 

 original cost was 8210,438.00. 



Mr. Hooper is a lumberman and not an 

 engineer. Nevertheless, it was he who 

 devised a plan for raising her. From photo- 

 graphs of her, maps and other data, he 

 decided that if all 

 the shell holes 

 were stopped, if 

 her sides were ex- 

 tended upward 

 until they pro- 

 truded out of the 

 water, and if the 

 water were then 

 pumped out of her 

 hold and out of 

 the extension top, 

 she would rise of 

 her own accord. 

 Why? Because 

 the volume of 

 water displaced 

 by the extension 

 form outweighed 

 the force tending to buoy her up, and when 

 removed left no alternative but for the 

 vessel to float. The form, or cofferdam, 

 as that kind of structure is known, was 

 built to displace 4,500 tons of water. 



There was assembled in San Francisco 

 and sent to Papeete the material for a 

 wooden cofferdam 307 feet by 14 feet in 

 height forward and 32 feet aft, plus an 

 additional 25-foot section in the form of a 

 V and also 32 feet high, to encompass the 

 stern. The material assembled included 

 some 600 tons of tongue-and-groove planks, 

 beams and joists, 13 tons of structural 

 iron, chains, hangers, pipes, etc., four direct 

 connected centrifugal pumps, one double- 



The Walkure rose to the surface like a cork 

 as the water was pumped out of the cofferdam 



action Worthington pump and two pul- 

 someters. 



Divers were sent down to patch up the 

 Walkure. Then the first 18-foot section of 

 the cofferdam, constructed on shore, was 

 lowered into place. The coft'erdam was 



constructed of 2-, 

 3- and 4-in. 

 planks, the thick- 

 ness increasing 

 with the depth of 

 immersion. These 

 were bolted and 

 nailed to the 

 joists, the entire 

 construction re- 

 sembling a huge 

 water-tight rec- 

 tangular box with- 

 out top or bottom. 

 Resistance 

 against t he exte- 

 rior crushing force 

 was secured by 

 use of transverse 

 beams 14 by 14 in., reinforced by longi- 

 tudinal supports 6x8 and 8 x 10 in., 

 tying together the different sections. 



Next the water was pumped out. When 

 the vessel floated a little she was towed 

 a little nearer shore. The first movement 

 of 125 feet was followed by a second of 

 146 feet on the following day. Pumping 

 was then stopped and five days spent in 

 sawing away the elevated portions of the 

 cofferdam in order to provide stability 

 and remove weight and topheaviness. 

 One day later the vessel was afloat on her 

 own bottom and the process of cleaning 

 up was begun. 



Four weeks were spent in getting the 



One of the shell holes made in the Walkiire's 

 hull after she was captured by the French 



How the big shell hole shown at the left 

 was plugged up before the pumping began 



