Behavior of Unusual Ship Forms 



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Fig. 2 - Hydrofoil semi- 

 submarine 



discuss today in the 3,000 ton class are very much competitive in the 2,000 mile 

 endurance range at a cruise speed of 20 knots. 



It is mainly our purpose in this paper to present comparisons of the several 

 unusual form ships based upon experimental information accumulated to date. 

 First we will take up the powering characteristics of these ships in both calm 

 and regular sea conditions and then go on to the motion characteristics under 

 these same conditions. It is of interest to point out that most of the results we 

 will present on the Hydrofoil Semi-Submarine and Large Bulb Ship are relatively 

 new and have not been discussed widely. Therefore, we will dwell in some de- 

 tail on some of the characteristics of these two particular ships. 



SPEED AND POWER BEHAVIOR 



The resistance characteristics of the Large Bulb Ship with the forward bulb 

 in various positions was investigated in the course of the study. As shown in 

 Fig. 3, the results for residual resistance are given for the various bulb posi- 

 tions, as well as for the bare hull, and it is seen that the most forward bulb 

 position results in substantial residual resistance reductions from the bare 

 hull as well as the other bulb positions over the speed range. It was this for- 

 ward bulb position that was used during the remainder of the study on ship mo- 

 tions. 



In order to establish the existence of an optimum form for the semi- 

 submarine hull, a study was made of streamlined body of revolution character- 

 istics in which it was discovered that in the high speed range, Froude number 

 in the vicinity of unity, the residual resistance coefficient of such bodies run- 

 ning near the surface can be considered to be approximately 25% of the deeply 

 submerged frictional resistance coefficient. Therefore, it was necessary only 



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