DATA ON HOG AND SAG OF MERCHANT VESSELS. 

 S. S. "Atlantic," June 7, 19 14. 



145 



Maximum deflection = 0.15 foot between 1.30 and 2.30 p. m 



It was a warm day — this was on the 7th of June — and the temperature difference between 

 the water and the hull ranged from .9° F., when the hull structure was cooler than the water 

 at 4.30 a.m., to plus 7° F. at 6.30 a.m.; at 8.30 a,m. it was up to 31° F., practically 32° F. ; 

 at 10.30 a.m. to 39°, at 12.30 p.m. it had gone to 40°, at 2.30 p.m. to 41°, and at 3.30 p.m. it 

 had begun to drop off down to 33°. 



Now the deflection in hundredths of a foot, under these conditions, counting from the 

 starting point as zero, and continually increasing to the maximum, had these values : The 

 first two hours showed practically no change; at 8.30 a.m. it had gone up to .05 of a foot, 

 at 10.30 a. m. it had gone .12 (this was plus), at 12.30 p.m. to .13, at 2.30 it was .13, 

 with a crest in between of .15, which is the interesting part, and at 4.30 it had dropped to .11. 



That was very interesting, and Ijefore we carried our final conclusions through it was 

 obviously necessary to take account of deflections due to temperature difference. The result 

 was that if we neglected temperature difference, when checking the theoretical deflection 

 calculations with the observations, the results were erratic. If we took account of temper- 

 ature conditions and corrected our observations (made for different conditions of loading 

 and extending through a number of months), to reduce them to a standard temperature 

 basis, we got a series of corrected deflections which tallied in with the theoretical results. 

 That was interesting, and I think it was helpful. 



The point is: Here we have deflections due to temperature of .15 foot. That is some- 

 thing over 1 y^ inches or 1 Y^ inches, perhaps. We are dealing with total deflections in most 

 cases of about 3 inches. I think that Mr. Combrooks' deflections are of about that same 

 order, and if we have the possibility of temperature variations injecting such a change as this 

 in the observations of deflections, it would seem that it would be desirable to have them 

 accounted for. 



I think it would be a great help to us and add to the value of the paper if Mr. Combrooks 

 would include in his statement any temperature data which was available, and also the 

 time interval which elapsed between the different observations, because from this table you 

 will notice as soon as the temperature begins to drop the deflection also begins to decrease, 

 but where the observations were taken at half-hourly periods it showed that the deflection 

 did not drop until the temperature drop had taken place; that is, the deflection of the whole 

 structure lagged behind the temperature change. 



