Hull Efficiency (η_H)

Compute η_H via coefficients (w, t) or via forces & speeds (T, R_T, V_a, V_s).

Method

Pick the route you have data for.

Ship speed V_s (kn)

Wake fraction w

If V_a blank → V_a = V_s(1−w)

Advance speed V_a (kn)

A) Coefficients Route

Thrust deduction t

If blank but R_T & T given → t = 1 − R_T/T

R_T (kN)

Thrust T (kN)

If T blank but t & R_T given → T = R_T/(1−t)

η_H = (1 − t) / (1 − w). Typically 0.95–1.3 depending on hull/prop interaction.

η_H: —

V_a used: — kn

w (if derived): —

t (if derived): —

P_E & P_T (if available): —

Mode A: η_H = (1−t)/(1−w). Mode B: η_H = (T·V_a)/(R_T·V_s).

Report: Hull Efficiency (η_H)

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Notes

Thrust–resistance relation: \( T = \dfrac{R_T}{1-t} \), advance speed: \( V_a = V_s(1-w) \).

Hull efficiency: \( \eta_H = \dfrac{1-t}{1-w} = \dfrac{P_T}{P_E} \), where \( P_T=T V_a \) and \( P_E=R_T V_s \).

Typical η_H ranges roughly 0.95–1.3; values >1 occur when wake fraction exceeds thrust deduction.