ABSTRACT 



The results of model tests performed to determine the feasibility of re- 

 ducing the pitching motion of the Mariner-type ship by means of fixed anti- 

 pitching fins at the bow are presented. A 20-foot self-propelled model represent- 

 ing the final design of the Mariner-type ship was tested in waves with four anti- 

 pitching fin configurations. Data are presented for both model and ship and are 

 summarized in dimensionless form. The data are also used to compute the effect 

 of the fins on the vertical motion and acceleration along the length of the ship. 



INTRODUCTION 



GENERAL 



A self-propelled model of the Mariner-type ship with and without antipitching bow fins 

 has been tested in waves at the David Taylor Model Basin. Four fins were fitted to a 

 Mariner model to determine the pitch reduction as a function of plan characteristics. 



The model, fins, and instrumentation used for the tests are described, and the exper- 

 imental results are presented and discussed. 



SHIP AND MODEL DESCRIPTION 



TMB Model 4414 with a linear ratio of 24.175, representing the final design of the 

 Mariner-type ship, was used for the tests. The principal characteristics of the ship and the 

 model are given in Table 1. 



TABLE 1 



Principal Characteristics of Mariner-Type Ship 

 and TMB Model 4414 



Item 



Ship 



Model 



Length, O.A. 



563 ft - 7% in. 



23.30 ft 



Length, B.P. 



528 ft - 6 in. 



21.85 ft 



Length, 25 ft - in. WL 



520 ft - in. 



21.34 ft 



Beam, Max. Molded 



76 ft - in. 



3.14 ft 



Draft, Load Line 



29 ft - 10 1/16 in. 



1.24 ft 



Displacement, Load Line 



21,093 tons 



3,252 lb 



Block Coeff., C B 



0.613 



0.613 



Load Waterplane Coeff., C w 



0.724 



0.724 



Design Speed 



20 knots 



- 



