190 



THEORY OF SEAKEEPING 



Table 5 MS San Francisco (from Schnadel, 1 936) 



Tafcl III. Sla I isti Iv. 

 M a X i Ml a I c .Slur m w e r I c*j . 



.MeUslelle M 46 



-Vnm,: Ilci »len ciDgeklainnterleu \\'erU'n ittt drr .\nU'il ili' 

 •) r>io Tafi-Iwerle cnlhallen den Anteil dcr Vihr.-tliun- 



SloU. 



fs ai)ffezot(eii. 



orbital velocitie.s of water particles by the .ship's body." 



(c) "In sagging conditions the stresses are larger than 

 in hogging because of the impact of waves again.st a 

 ship's bottom. 



(r/) "The calculations of the longitudinal strength 

 of .ships must be modified. For the real stresses of ships 

 at sea, higher wave heights must be taken for sagging 

 than for hogging conditions. The relationships can be 

 taken from the foregoing research for ships of low engine 

 power. For faster large ships these must be increased. 



(e) "The usual methods of calculation of bending 

 moments, bending stresses and deflections from moments 

 and compressive forces are satisfactory for practical pur- 

 poses. The wave length ecjual to ship length must be 

 chosen for calculations as before." 



Slamming was observed during the storm. The 

 slamming accelerations were low because the ship was 

 in the hove-to condition. 



-^ Unexpectedly low bending stresses were found later by E. V. 

 Lewis (19.56!)) in towing-tanl< tests. This phenomenon can be 

 readily explained on the b.asis of the work of Korvin-Kroiikovsky 

 and Jacobs (Ut57), and Jacobs (5-1958). It was shown that the 

 Smith effect is apjiroximatuly doubled with inclusion of the bodj'- 

 wave interference effect. 



Stereophotographic measurements by Weinblum and 

 Block (1936) had no direct connection with the ship's 

 motions and stresses. Thej^ recorded the sea surface 

 contours a short distance in front of the ship. They 

 \'i\'idly demonstrated the irregularity of the storm sea 

 and confirmed the magnitude of the wave heights ob- 

 tained by extrapolation of the profile measured at the 

 ship's sides. However, it is virtually impossible to 

 apply these data to the quantitative study of wave 

 properties by modern statistical methods because stereo- 

 photographs give samplings of small sea areas at isolated 

 in,stants. 



5.13 Admiralty Ship Welding Committee — SS Ocean 

 Vulcan. Observations aboard the SS Ocean Vulcan were 

 made as a part of a broad program initiated by the Ad- 

 miralty Ship Welding Committee (England). Under 

 this program the structural responses of riveted and 

 welded ships were compared. The entire work was 

 described in the following reports.-^ 



'^ These reports are obtainable from H.M. (Stationary Office, 

 P.O. Box 569, S.K. 1, London, England, or in the United .'States of 

 .\merica from British Information iServices, 30 Rockefeller Plaza, 

 New York 20, N. Y. 



