Sec. 18.17 



MODEL-TESTING PROGRAM FOR A SHIP 



879 



Ship Speed, Kt 



Fig. 78.1 Plot of Data From Self-Propelled 

 Test of Aech-Stern ABC Ship 



Lw/I^shiv > based on 20.5 kt as a reference smooth- 

 water speed for the ship, when towing at constant 

 thrust through simple, regular waves having 

 varied lengths. (No wavegoing model was made 

 of either ABC design) . 



(12) Photographs showing ship behavior at 

 extreme up- and down-pitch positions, in waves 

 of the most unfavorable length (when the ship is 

 wettest). (No test). 



78,16 Test Results for Models of the ABC 

 Ship. The data derived from the tests of TMB 

 models 4505 and 4505-1 are reported here by- 

 preparing and reproducing sets of SNAME RD, 

 PD, and SPD sheets, of the type in use at the 

 date of calculation (1954). These sets are complete 

 except for the drawing of TMB model propeller 

 1986, used on the arch-stern model, and for the 

 body plans and profiles of the ends, to be found 

 in Chaps. 66 and 67. 



An index to the respective figure numbers and 

 sheet titles follows: 



Figs. 78.Ja SNAME Resistance Data sheets for TMB 

 and 78. Jb model 4505, representing ABC transom- 

 stern design 

 Figs. 78.Jb SNAME Expanded Resistance Data sheets 



and 78. Jc for TMB model 4505, for 400-ft length 



Figs. 78.Ka SNAME Resistance Data sheets for TMB 

 and 78.Kb model 4505-1, representing ABC arch- 

 stern ship 

 Figs. 78.Kb SNAME Expanded Resistance Data sheet 



and 78.Kc for TMB model 4505-1, for 400-ft length 



Fig. 78.L EMB model propeller 2294 



Figs. 78.Ma SNAME Propeller Data sheets for EMB 



and 78.Mb model 2294 (cavitation test not made) 



and 78.Mc 



Figs. 78.Na SNAME Self-Propulsion Data sheets for 



and 78.Nb TMB model 4505 (transom-stem design) 



and 78.Nc driven by EMB model propeller 2294. 



Model propellers 1986 and 2294 were buUt at 

 the old Experimental Model Basin in Washington 

 but were transferred in 1940 to the David Taylor 

 Model Basin. The identifying abbreviations 

 "EMB" and "TMB" are therefore interchange- 

 able. 



A much more comprehensive and detailed 

 account of the model testing on this project has 

 been prepared by Commander E. R. Meyer, USN, 

 who participated in the testing. This has been 

 issued as TMB Report 1006, February 1957. 



The reader will note that some of the symbols 

 on the RD, PD, and SPD sheets of Figs. 78.J 

 through 78.N are not those approved by the 

 ATTC and ITTC, and do not conform to those 

 hsted in Appendix 1. This is because the SNAME 

 data-collection program on models was begun 

 several years before approval of the now-standard 

 symbols. It has been considered preferable to 

 retain certain older symbols and abbreviations, 

 such as EHP, e, and the like, in order to present 

 the data consistently on all sheets. The reader 

 should have no difficulty in making the transition 

 to modern standards. 



78.17 Comments on Model Tests and Analy- 

 sis of Data. During all ABC model tests more 

 readings were taken, and over a wider speed 

 range, than is customary for the usual merchant- 

 vessel hull form. The procedure was first to cover 

 the entire range with about ten readings. The 

 speed range was then run through a second and 

 third time, using about the same number of 

 readings at intermediate speeds. After complete 

 coverage was obtained in this manner, additional 

 runs were made to recheck certain spots or to 

 fill in critical sections of the resistance curve 

 where rapid changes were occurring. 



This method of testing, as contrasted to ruiming 

 once through the speed range in the usual pro- 

 gressive manner, from low to high values, can be 

 expected to give more scatter in the test spots. 

 On the other hand, it gives more validity to the 

 test results. It is considered remarkable that all 

 the test spots for each of the ABC models, ob- 

 tained during a day's running, fell into a smooth 

 pattern. 



