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along the edges. Copper sheathing would similarly be used on a 

 copper-fastened hull. 



NavShips 250-336 gives the following particulars concerning 

 wooden sheathing : 



Wood sheathing, in order to give adequate protection to the hull 

 against ice and marine organism attack, should begin at a point above 

 the load water line when the vessel is at her deepest draft and com- 

 pletely enclose the hull, including tlie keel and all deadwood, the 

 sternpost, the wood skeg, if any, and all other exposed parts of wood. 

 The thickness of this sheathing varies from approximately one-half 

 inch to 2 inches, according to the size of the vessel. The keel shoe 

 should be sufficiently wider tlian the keel to cover the bottom edges 

 of the sheathing fastened to the keel. If it is not, the shoe itself 

 should also be protected by sheathing. 



When sheathing is used for protection against ice alone, it should 

 extend high enough up the sides of the hull to form a belt of suffi- 

 cient width to afford adequate protection against floating ice at any 

 draft. This may require spiling of the sheathing strakes. Sheathing 

 for this purpose is secured to the shell of the vessel generally by 

 means of screws, the heads being slightly below the surface of the 

 sheathing. A metal cutwater should either be placed over the stem 

 iron or butted and welded to the aft face of the stem iron. This cut- 

 water should extend vertically across the width of the sheathing belt 

 and sufficiently far aft to provide the proper cutting action when ice 

 fields are entered, thereby protecting the forward edges of the wood 

 sheathing. The portion of wood sheathing that is placed under this 

 metal cutwater should be tapered. 



Ice sheathing requires wood capable of resisting severe abrasive 

 action and which can hold fastenings well. The species preferred 

 for this purpose is Australian ironwood. White oak has given satis- 

 factory service. Other species having the properties that indicate 

 tliey could be used satisfactorily are red oak, hickory, pecan, and rock 

 elm. Black locust and live oak also have the required properties 

 but are not readily available. The properties of the foregoing woods 

 responsible for their selection are high toughness and hardness. 

 White oak is used almost exclusively for keel shoes for the same 

 reason that it is used for protection against ice. 



9. Bracing in how. — If feasible, install timber bracing in the fore- 

 peak, using horizontal "ice beams" extending from side to side at the 

 load water line and bearing on fore and aft planks placed between 

 the frames. Additional support to the fore peak bulkliead on the 



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