Motion and Resistance of a Low-Waterplane Catamaran 



shown in Table 1. The results in figure 4 are extracted from Jones 

 (1972) and are nondimensional values defined by 



A 33 _ B 33 



A 33=l^ B 33 



V77 



MVe / L 



A „ or A r B _ or B 



-T- -a- 35 53 35 53 



A „ or A„ = B_ or B 



'35 53 ,, , 35 53 



V 



M L MVeL 



A 55 _ B 55 



A 55~ WT 2 B 55 



ML ML yjgL 



- aF 



g 



The experimental results are taken at several amplitudes of oscilla- 

 tion. Agreement between the theoretical and the experimental results 

 is good for the zero-speed case, whereas some discrepancies can 

 be observed for the case of F n = 0. 253. 



Comparison of theoretical and experimental values of non- 

 dimensional heave amplitude ? / A and pitch amplitude £ X/(2 7rAJ 

 versus wavelength X/L for the catamarans shown in figure 5 are 

 presented in figures 6 through 8 . A is the wave amplitude, X is 

 the wavelength, and L is the ship length. Most of the results shown 

 in these figures are from Jones (1972). 



Unrealistically high- spiked theoretical values of heave and 

 pitch amplitudes for 30 knots shown in figure 8 imply that damping 

 values obtained from theory have been underestimated. The deficien- 

 cy of theory may be traced to several assumptions or approximations 

 made in the present analysis : the ideal-fluid assumption, the strip 

 approximation of three-dimensional hydrodynamic coefficients, and 

 the assumption of neglecting the second-order effect of coupling bet- 

 ween the steady and oscillatory perturbation potentials. None of these 

 assumptions can be removed without undergoing major renovations 

 in the analytical procedures. 



Nevertheless, an attempt to introduce supplemental damp- 

 ing in the equations of motion has been made by using a trial-and- 

 error approach. The first approach attempted was to express the 



491 



