sequently, there is room for considerable improvement in connection with prediction 

 of slamming, propeller emergence, speed reduction, water over the bow, pitching axis 

 location, etc. 



4. The effect of transients in irregular seas was investigated considering a 

 trend of waves of constant length and variable height. The steady state response was 

 compared, cycle by cycle with the measured response in ref. 1. 



5. The influence of the block coefficient on the time and space dependence 

 of the impact pressure was investigated and pressure mappings were computed [ref. 

 4]. The computed values are presently being compared with experimental results. 

 Correlation between slamming pressure and acceleration are given in ref. 5. 



6. It is felt that the new slamming model proposed by Dr. Weinblum has 

 merits for so-called flat impacts. The practical importance and the usefulness of the 

 "enclosed cavity" approach will have to be shown before this model can take over 

 the presently established and practically useful methods based on Wagner's idea [ref. 6], 



7. Head-on collision type impacts were observed and reported in ref. 7. Longi- 

 tudinal accelerations amounting to 0.1 to 0.2g were recorded in heavy head seas on 

 destroyers. Such values can be arrived at using Wagner's method to compute forces 

 developed during water entry. 



REFERENCES 



1. Pournaras, U., "Seaworthiness of a Mariner Class Ship Equipped with Bow Anti-pitching 



Fins", TMB Report 1084. 



2. Pournaras, U., "Pitch Reduction with Bow Fins of the Series 60, 0.60 Block Model", 



TMB Report 1061. 



3. Bledsoe, M. D., "Speed Reduction in Waves", TMB Report 1083. 



4. Bledsoe, M. D., "Series Investigation of Slamming Pressure", TMB Report 1043. 



5. Zarnick, E. E. and Szebehely, V. G., "Hydrodynamic Impact Measurements", Proc. First 



Conference on Coastal Eng. Inst., 1955. 



6. Wagner, H., "Uber Stoss und Gleitvorgange". ZAMM, Vol. 12, p. 193. 



7. Szebehely, V. G., "loint USN-RNN Seakeeping Trials", Naval Research Reviews, Sep- 



tember 1956. 



/. F. Allan 



I think it is interesting to note that since the classical analysis and presentation 

 of Krylov, there has been very little real development of the subject until the last ten 

 years or so. In that recent period the interest in the behavior of ships at sea, and 

 the interest in the possibility of analyzing that against the mathematical theory has 

 grown enormously. 



I wish to pay a tribute to the enormous amount of work which has been done 

 in this direction in the United States, both at the David Taylor Model Basin, and the 

 Stevens Institute. This work has been presented in a number of papers, and it really 

 places a very useful tool in our hands. 



One should mention in passing, the work that Kent did at Teddington in the 

 1920's and 1930's, the chief point of which might be considered to be the indication 

 of the importance of the relationship between the downward motion of the bow and 

 the actual position of the bow wave. The recent work has shown how the theory 

 explains a number of these characteristics, but, unfortunately, the accuracy of the 

 theory and our knowledge of the characteristics is such that it is not reasonable to 

 come to detailed conclusions on the comparisons. The broad picture is clear, but one 

 cannot pursue it in too much detail. 



Probably the most significant indication, from the recent developments, is to 

 show, or to suggest that the only really effective way of improving the seagoing quality 

 of ships is to increase the damping factors. 



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