AND THOSE MEASURED WHILE RECEIVING CARGO. 127 



I think that is a thing which we probably had not realized before, and it is, perhaps, a little 

 hard to understand. 



Mr. Elmer A. Sperry, Member: — I do not think Mr. Howard should feel that a failure 

 to discuss this paper is any indication of a want of appreciation of its value. I think it is 

 one of the most remarkable papers of the session. The stresses on the deck plates are of 

 rather peculiar nature, and I think there is one point that might shed some light on these 

 stresses, especially the marginal stresses as compared with the stresses along the ttiidship 

 axis as shown by the diagram. 



Last year when we were running some tests at sea it 'became necessary to determine if 

 there were any stresses set up in the hull, beams, or deck structure, due to stabilizing the 

 ship in heavy weather. They crawled in every available space and watched the joints with great 

 care, but the work was done so easily and naturally that no stresses made themselves mani- 

 fest at any point. After the work was finished some of the joints were opened and ex- 

 amined, which confirmed this. Under these conditions it would have been interesting to have 

 had some of these instruments installed at various points to ascertain the character and direc- 

 tion of the small stresses that had been calculated and were known to exist. 



However, there seems to me to be one point that should not be overlooked, namely, the 

 torque stresses. If we take a tube — that is, a long tube — we have a very stable structure with 

 reference to torque moments. If we secure one end of this tube and apply torque stresses to 

 the other it will be found that only a very slight give, or spring, will occur. Suppose we 

 take this cylindrical tube and shave it down horizontally, or saw it in two, so that we have a 

 gutter ; now can any one of you imagine what the torque value of that gutter is as compared 

 with the torque value of the tube out of which the gutter was made ? Calculations show 

 that it is only 1/3600. Now, then, a ship is a gutter with a deck or decks across it, and it has 

 been known for years that ships, especially ships such as torpedo-boat destroyers, long and 

 slender, and where the plating is as light in thickness as is consistent with safety, will yield 

 quite considerably to warping moments. As we analyze these torque strains, which always 

 come in rough weather, we find that the marginal portions of the deck are the portions which 

 must receive and sustain certain of these strains. This introduces quite a wide variation in 

 the stresses between the marginal and central regions of the decking and should, of course, be 

 taken into consideration in connection with observations such as have been undertaken by 

 Mr. Howard. 



In prosecuting investigations such as these it would seem to me that if these instru- 

 ments could be made recording, being plotted a against time, it would then be possible to trace 

 the cycle of stresses, aiding materially in their proper interpretation. 



Mr. Francis T. Bowles, Past President: — I suggest that Mr. Howard tell us whether 

 this apparatus of his has been used on other structures to determine live load, and if so, 

 where; in other words, give us some idea of the reliability of the instrument and how he 

 came to make this test on this vessel, and whether he is at liberty to make it on other 

 vessels. 



Mr. Francis B. Smith, Member: — I ask Mr. Howard if he noted, at the time the boat 

 took on cargo, if the draught of a vessel was affected in the marks forward and aft by the 

 different temperatures of the deck. We have reports of that kind on our ships quite fre- 

 quently. We are in the Lake trade. When our boats load at the head of Lake Superior and 

 go down to the Sault Canal, where the draught is limited by the draught of water in the 



