COEFFICIENTS, THRUST AND TONNAGE

coef thumb

Coefficient of fineness of water plane   

Cwp = Aw / Lwl

Midship section coefficient   

CM = AM / BT

 Block coefficient     

CB=Displ./ BTLPP  

Prismatic coefficient  

CP=Displ. / AMLPP 

Vertical prismatic coefficient   

CVP =Displ./ AWT

Resistance

R=Sρv2(rf +rw)/2

S=underwater area;  ρ =water density; v=speed; rf, rw=resistance coefficients (roughness, wave and shape)

Engine power

Peng =Rv (1-t)η /(1-w)

t=suction coefficient; η=propeller efficiency

Resistance coefficient 

Rez = R / ρv2L2 

Reynolds number  

Re = ρvD / μ

Froude number  

Fr = v / (gD)1/2 

Thrust coefficient  

KT = T / ρn2D4

T- thrust 

Unknown

Gross tonnage          GT = K x V

                                    K = 0.2 + 0.02 x log10V

Net tonnage             NT = K2 x 4D2 x VC

                                   V – cargo volume

                                   K2 = 0.2 + 0.02 x log10VC

Compensated gross tonnage

                                  CGT = a x GTb

where a and b as defined by OECD

Directorate for Science , Technology and Industry (STI) 

“Compensated Gross Ton (CGT) System” 

Estimated:

Gross tonnage    GT = 0.35LBDCB

 CB   – slow ships  0.80 -0.85

        - conventional ships 0.70 – 0.80

        - fast ships 0.65 – 0.70

Net tonnage       NT = 30% of GT

PDF document : Coefficients, thrust and tonnage

See also: SHIP DIMENSIONS AND TONNAGE

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