assumed in the. absence of specific data for such tests at the Taylor Model Basin. The smaller 

 value was chosen in view of the intended location of most of the massive items of equipment- 

 the winch and stowage reel for deep-sea cable and the main propulsion plant. These, with 

 most of the fuel, will be located in the middle half-length of the ship. 



MODEL TESTS 



The tests were conducted in the 140-foot basin, using a pneumatic wavemaker and a 

 gravity-type dynamometer. 



Wavelengths corresponding to 127.5, 170, 204, and 340 feet (X/L = 0.75, 1.0, 1.2, 2.0) 

 were used, each with X/h values of 20, 30, and 40. The model was tested in head seas using 

 tow forces corresponding to still-water speeds of 6 and 12 knots. Pitch, heave, and speed 

 were measured for these conditions. 



The model was also run in several sea conditions with her stern to the sea, viz., 

 A = 0.75L, 1.0L, 1.2L, and 2.0L, all at a/A = 20. These tests were for qualitative results, 

 no measurements of pitch and heave being taken. 



The measurements of total resistance in still water were obtained incidentally in order 

 to determine the data necessary to carry out the tests. It is considered that scaling of resis- 

 tance data from a 5-foot model to full scale is of doubtful validity. The resistance curve is 

 given , Figure 5, page 9, merely to indicate the reproducibility of the data. 



RESULTS AND DISCUSSION 



The results of the tests are presented in Figures 3 and 4 and Table 2. Figure 3 shows 

 the reduction of speed in waves; the tow force and the A/A ratio are constant for each curve; 

 speed is plotted against wavelength. The magnitude of pitch and heave are shown in Figures 

 4a through 4d; each figure involves a single wavelength and each curve represents amplitude 

 of motion plotted against speed for a constant ratio of X/h. The speed V R which would pro- 

 duce resonance in pitch— the most violent motion for a given wavelength should be expected 

 at this speed— is shown for each wavelength. 



As the curves show, reduction of speed in waves is in some cases quite drastic. How- 

 ever, in heavy weather, ship speed is more likely to be determined by the master, in the interest 

 of safety and comfort, rather than by lack of power, tligh speed is useful mainly in traveling 

 to and from station, so that a ship which can make 7 or 8 knots in a state 4 sea would probably 

 be quite satisfactory from the standpoint of speed. 



As to the observed pitching and heaving, they, too, are quite drastic on occasion, and 

 are considerable throughout most of the conditions investigated. Unfortunately this behavior 

 is characteristic of small ships in large waves. Table 2 shows that the pitch amplitude re- 

 ferred to the maximum slope of the exciting wave (column \b /■& ) is never larger than 1.12, 



