2S0 Explanation of certain Iinprouemenis 



coacenis of Britain, in the Geological department of vour very 

 useful work, 



I remain, sir, 



Your obedient servant, 

 April 4, 1815. A Constant Readkr. 



L. Explanation of certain Improvemeiit^ in the Constnictlon 

 and Fastening of the Frame Timbers of Ships or Vessels, either 

 when Building, or when und'jr Repair, for the more effectually 

 preventing the Disunion of the Parts caused ly Hogging, and 

 the transverse Bending of the Hull, By ^Ir. John Wal- 

 TEiis, Architect, Fenchurch Buildings, London. 



JcSefore I proceed to explain the proposed improvements, it is 

 necessary to give an idea of the common method of ship-building, 

 and of tlie principal improvements which the art has hitherto 

 received. 



The frame or skeleton of a ship, built according to the com- 

 mon mode of construction, is composed of a number of curved 

 timbers (called ribs) placed at certain distances from each other, 

 in planes, at right angles to the keel on which they all rest. In 

 the intermediate spaces between the said ribs, are placed filling 

 timbers, answering to the curve of the ribs, so that the void be- 

 tween timber and timber is from one to five inches. Athwart 

 tliis frame are laid beams, at right angles to the keel, serving to 

 hold together the sides of the ship and to support the decks. 

 And for the purpose of strengthening the parts, a second range 

 of curved timi)ers or inside ribs (called riders) are placed over 

 the interior planking, but at a greater distance from each other 

 tli^m the ribs properly so called. 



As in this construction all the timbers are disposed at right 

 angles to the keel and keelson, and the planking both within and 

 without is longitudinal, there is evidently no mechftuical sup- 

 port to resist the action of gravity, from which radical defect all 

 .ships have a tendency to arch longitudinally and bend trans- 

 versely by the sinking of the sides. The remedy of these evils 

 is a great desideratum in naval architecture. 



The constant strain which a ship experiences from an un- 

 equal distribution of v.eight, and the upward pressure of the 

 water, is the cause of its becoming arched throughout its length, 

 or (as it is called) hogged, to which cause may be added the 

 partial pressure of the water in a longitudinal direction, which 

 tends to compress the keel, and thereby to increase the curvature. 

 The degree of carvature produced by these combined causes 



is 



