High Speed Displacement-Type Hulls 
B = Beam (waterline), feet 
g = Gravitational constant, ft/sec” 
D = Depth of water, feet 
Cg = Block coefficient 
Resistance 
V/VL = Speed/length ratio 
B = Froude number V/ VeL 
0100 = Froude skin friction coefficient for 100-foot ship 
Or = Froude skin friction coefficient for L-foot ship 
© = Wetted surface x 0.09346 / A248 
@© = =Froude speed/length ratio = 1.055 V/V. 
2 
ee 0 (+) L 
1.319 
VL] Ae 
r = Resistance, pounds 
© = 2epx 427.1 
V3A 28 
Propulsion 
t = Thrust deduction 
Nh = Hull efficiency 
1, = Relative rotative efficiency 
We = Open water propeller efficiency 
n = Quasi-propulsive coefficient 
wy = Froude wake fraction 
We = Tayler wake fraction 
dhp = Delivered horsepower at propeller 
ehp = Effective horsepower = © V2A2/ 427.1 
Note: The constants used above are for ships in salt water. 
REFERENCES 
[1] Kafali, K., “The Powering of Round Bottom Motor Boats,” International Shipbuilding 
Progress, Vol. 6, No. 54, Feb. 1959 
597 
