462 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 66.2 



speed is specified in the river leading out from 

 Port Correo and no safe speed can be predicted 

 until the size and shape of the vessel is known. 

 Past experience with smaller vessels, however, 

 indicates that this may be hmited to 13 or 14 kt, 

 reckoned as speed through the water rather than 

 speed over the ground. 



The layover, standby, and maneuvering times 

 are then set down, in hours, as in the upper part 

 of Table 66. c, starting with the beginning of a 

 voyage at Port Amalo. Opposite these are marked 

 the estimated average fuel-consumption rates for 

 the periods given, intended to cover all auxiliary 

 as well as propelling-plant loads. These rates are 

 expressed as fractions of the fuel-consumption 



rate at the maximum designed power. Multiplying 

 these average fractions by the hours during which 

 fuel is burned at the corresponding rate gives the 

 corresponding hours during which the consump- 

 tion would be the same if the vessel were steaming 

 at maximum designed power. 



The elapsed times for the underway sectors are 

 then calculated, as shown in the lower part of 

 Table 66. c. In the open sea, it is assumed that 

 the fuel consumption for each hour is that 

 corresponding to the designed maximum power, 

 despite the fact that the actual speed is generally 

 less, averaging 18.7 kt as compared to 20.5 kt or 

 slightly more, and that the elapsed time is longer. 

 This extra fuel, calculated as necessary but not 



TABLE 66.0 — Fuel Consumption Rates fob Voyage Components 

 The expression rated fuel signifies the rate of fuel consumption at maximum designed power, all services in operation. 



•14 kt less 2.75 kt for adverse current is 11.25 kt; 



13 kt less 1.5 kt for the same is 11.5 kt 

 '14 kt plus 1.5 kt favorable current is 15.5 kt; 



13 kt plus 2.75 kt favorable current is 15.75 kt 



