872 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 7S.6 



TABLE 78.C — Weight and Volume Data for 

 Model Resistance Tests 



All resistance tests in the designed-load condition are 

 to be run at zero trim fore and aft. 



All figures given are subject to minor changes as the 

 designs proceed but wiU be made firm before the first 

 model resistance tests are run. 



Net volume to 26-ft DWL 579,682 ft' 583,251 ft' 



Corresponding weight displace- 

 ment in standard salt water, 

 34.977 ft' per long ton, 59 deg F 16,573 t 16,675 t 



NOTE: — The following data are given for information and 

 comparison only: 



Item 



Transom- Arch- 

 stern hull stern hull 



Bare-hull weight displacement 

 Shell plating and appendages 



16,461 t 

 112 t 



16,567 t 

 108 t 



(3) It is preferable, when testing to determine 

 the drag effects of the appendages, not to change 

 both the form and the weight of the model at 

 the same time. For the two ABC hulls the weight 

 change is of the order of 0.7 per cent. 



(4) Long experience indicates that the test 

 results are more consistent if the weight of the 

 model is kept constant for both bare-hull and 

 all-appendage (including plating) conflitions. 



The calculated volume and weight data for the 

 two alternative designs, following the procedure 

 described, are hsted in Table 78. c. 



From Sec. 66.32 and Fig. 66.T, the weight dis- 

 placement at the light-load Condition 3 is 12,090 

 tons. The model weight for this condition, taking 

 X' = 16,581, is (12,090) (2,240)716,581 = 1,6331b. 

 Deducting the weight of ballast necessary to trim 

 the model by the stern to a 23-ft draft at the AP 

 for the ship, it is believed that this leaves sufficient 

 structural weight for a two-part wax model of 

 block coefficient about 0.60, Avith midship trans- 

 verse bulkheads and connecting bolts. 



78.6 Resistance Tests. Bare-hull resistance 

 tests are first to be run on the models of both 

 designs. After observation and photographing of 

 the wave profiles, hues of flow over the hull, and 

 flow details around the stern, as specified for the 

 bare hulls in the sections following, resistance 

 tests are to be run with both models when fitted 

 with all appendages. 



The range of speed for all resistance tests listed 

 in the foregoing and for the self-propulsion tests 

 listed subsequently is from approximately 0.3 to 

 at least 1.1 times the expected smooth-and-deep- 

 water speed at 0.95 of maximum designed power, 



Fig. 78.A TMB Model 4505 Floating at Designed Draft and Trim 

 In this photograph, and in others of this chapter, the original exposures were made with the bow of the model facing 

 toward the left, in unconventional fashion. They have not been reversed, left for right, because of the numbering and 

 lettering that would likewise have been reversed. 



