n degrees 



o c 





With«jt 



Fins 



1 









x: 

 o 



a. 









"O 



® 80 





-£-=1.406-7 











or 





XJ.I72 





<■> 



> 

 o 

 a> 



X 





O.SZl^s' 





o. 40 



_l 















(0 



a 









a. 









*? 









k. 



r-», 



'^^ — 



|\ U72^"~"~ 



\ 





With Fins 





0.937 



0.10 0.20 



Froude Number, F n 



0.30 



0.10 0.20 



Froude Number, F n 



0.30 



Figure 18 — Phase Lag of Heave Referred to Pitch 



of the comparative performance of the various fin configurations is presented under 

 "Discussion of Results." 



SUMMARY OF TEST RESULTS (Figures 16 through 18) 



The test data are summarized graphically in Figures 16, 17, and 18, presenting pitch, 

 heave, and phase angles, respectively, for the Mariner-type ship with and without antipitching 

 fins. 



DISCUSSION OF RESULTS 



The results of the model tests indicate the feasibility of reducing the amplitude of 

 pitch of the Mariner by means of antipitching fins installed at the bow of the ship. The 

 numerical value of the full-scale pitch reduction, however, may be influenced by scale effects. 



The tests at the lighter load conditions, corresponding to 15,870 tons and mean draft 

 of 23 feet with 4-foot trim by the stern, showed small differences of pitch and heave amplitudes 

 compared with the results of the tests at the heavier load condition. The general behavior of 

 the model in the regular tank waves was, however, much worse in the lighter condition. Fore- 

 foot emergence and slamming occurred frequently. This can be attributed to the shallow draft 

 of 21 feet forward, and possibly unfavorable phase relationship between the heaving and 



27 



