OF SHIP CONSTRUCTION. 



67 



the corresponding points in the transversely framed vessel, thus introducing the 

 factor of a lever arm. It is impossible to express this difference mathematically, if, 

 indeed, such an expression should be desired, and consequently the difference has 

 been omitted in these calculations. It should be remembered, however, that this 

 omission makes the exactness of the conclusions somew^hat doubtful, the doubt be- 

 ing in favor of the Isherwood ship. 



Calculating the strength at the points indicated above, using the same reason- 

 ing as for the transversely framed vessel, but including as part of the transverse at 

 longitudinal No. 14 a strip of the shell plating equal in v^idth to only one and one- 

 half times the combined width of the shell clip flanges, since a double angle connec- 

 tion is here used, we have, for the bilge connection, a section modulus of 241.0 

 inches^; for the second deck connection, a section modulus of 41.7 inches^; or a total 

 of 565.4 inches^ for both sides. 



The modulus for the upper deck connection is 47.5 inches^ giving a total of 

 660.4 inches^ for both sides of the entire section. The transverse spacing being 12 

 feet (except in the peaks and forward of the three-fifths length), the combined sec- 

 tion modulus per foot length of the ship becomes 47.1 inches^ excluding the upper 

 deck, and 55 inches^ including the upper deck. 



Summary. — For more ready comparison we may summarize these section 

 moduli as follows, the values being given in inches^ for both sides of the vessel : — 



It will be noted that the Isherwood vessel compares very favorably with the 

 transversely framed ship as far as the total resistance to diagonal distortion is con- 

 cerned. The Isherwood bilge connection develops 70.6 per cent more strength than 

 the corresponding connection in the older S3^stem of framing, while the Isherwood 

 deck connections are weaker. And it may be argued that this is a more favorable 

 distribution of strength, since the bilge connection is continuously subjected to se- 

 vere stresses due to the water head. There is unquestionably some justification for 

 this viewpoint, provided that the deck connections are not weakened to such an ex- 

 tent as to make the decks themselves unsafe. This question will, however, be con- 

 sidered separately under the head of "Strength of Decks." 



