264 



THEORY OF SEAKEEPING 



Momen+ by S+rain-Measuremen+ 



Momen+ by Calcula+lon 



''i'Z^„\„„ ^ — End of Erection 



■lagging 



10 20 30 40 50 



Meter 



Fig. 8 Bending moment by strain measurement and by calculation (fro 71 Schnadsl, 1937-1938) 



Deflection by Shearing Forces 



Hogging (40") 

 -o« 



Optograph- Measurement 



Sagging (45-45 ) 



Resulting Deflection CCalculated) 



10 20 30 40 50 



Meter 



Fig. 9 Deflections by optograph measurement and by moments and shearing forces. Time: 1 1. xii. 34, 1 Ih. 40' 



(from Schnadel, 1937-1938) 



The Ocean Vulcan reports contain a large amount of 

 miscellaneous useful information, but the complete 

 wave profile is shown for only two cases, Fig. 3-41. In 

 most ca.ses, the water profiles recortled on the ship's sides 

 were not used to define the ambient sea waves. The 

 instrumentation, which was used for this purpose, was 

 similar to Schnadel's. The larger number of observa- 

 tion stations could have been e.xpected to give a greater 

 accuracy. However, an opinion was expressed that 

 Schnadel's method of evaluating ocean-wave profiles 

 had not been reliable and apparently the Ocean Vulcan 

 data were not used for this purpose. Ship attitudes and 

 wave profiles on the ship's sides were presented in the 

 final reports only in the form of crude sketches which are 

 not suitable for further analysis. The observed and 

 calculated stresses were referred to the visual wave ob- 



servations and to weather forecasts of the Admiralty. 



The bending moments were calculated for a number of 

 instances on the basis of accelerometer and water- 

 pressure readings as this had been done by Schnadel. 

 Results of these calculations were compared to the results 

 of strain-gage readings. A satisfactory agreement was 

 shown to exist. An example of this comparison is shown 

 in Fig. 3-3(3. 



A .sample of calculations of bending moments is pre- 

 sented in Table 3." The instant to which this table 

 refers, is indicated by the film frame No. 300. This is 

 0.96 sec earlier than the position labelled "po.sition at 

 film No. 302" on the upper part of Fig. 3-41. The 

 reader's attention is called to the fact that in this case 



" Reproduced from Table 29, page 116 of Admiralty Ship Weld- 

 ing Committee report no. 8. 



