Ship Maneuvering in Deep and Confined Waters 



Fig. 41, 98 000 tdw tanker — Low speed spiral diagram from 

 computer predictions for deep and shallow water 



A similar trend is not unique, but it shall be observed that it may- 

 be necessary to include higher order derivatives in t, to account 

 for a finite range of "dangerous depth" as defined by Fujino, [5]. 



Figure 42 shows predictions for 20° rudder step responses 

 in change of heading, yaw rate, and drift angle. The small drift 

 angle obtained in the shallow water case is associated with the large 

 increase of cross -flow drag. Similar results have earlier been 

 reported by Schmidt-Stiebitz, [99], 



From simulator and full scale experience is known that the 

 helmsman may have some difficulties of controlling the ship in 

 maneuvers that involve a change of course in shallow waters. 

 Maneuvers by use of auto pilots are repeatable and well suited for 



893 



