(4) Deck traverse (Optional) - Where required to identify 

 a particular hull mode, vertical amplitude should be measured on the 

 main or strength deck level, on the centerline, at a sufficient number 

 of points to permit determining the approximate location of all nodes. 

 If instrumentation permits, use of both a roving pickup and a fixed 

 pickup at the stern will simplify location of nodes by detecting phase 

 changes . 



f . The quantities to be measured are: 



(1) Displacement amplitude, in mils single amplitude 



(t .001 in.). 



(2) Wave form (recorded by the oscillograph). 



(3) RPM (by the addition of a time marker, or through 

 the known paper speed. Actual RPM can usually be computed from the 

 oscillograph record. It is desirable, in addition, to record the RPM 

 obtained from the ship's instruments). 



(4) Frequencies (obtained from the oscillograph record). 

 Measurements should be made by an electronic system which produces 

 a permanent record, and preferably consisting of velocity -type trans- 

 ducers (which produce a signal proportional to velocity), integrator, 

 amplifier and recorders. 



TEST PROCEDURE 



a. Determine principal ship characteristics, (a good example 

 of the desired detail is given in the Sample Test Report). 



(1) Ship dimensions 



(2) Propeller type, dimensions and number of blades. 



(3) Propeller aperture clearances. 



(4) After -body configuration (include about one -fourth 

 the length of the ship). 



(5) Power plant description. 



(6) SHP, RPM and speed for various ratings at specified 

 displacement. 



(7) Shaft train dimensions (shaft material and diameter, 

 bearing locations, and method of thrust bearing attachment). 



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