Appendage & Roughness Allowance

Add hull-roughness ΔCf and appendage form-factor ΔC allowances to the bare-hull frictional coefficient. Standard ITTC-78 corrections for ship-power prediction.

DesignResistance

Loading calculator…

This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

\Delta C_F = \left[ 105 \left( \frac{k_s}{L_\text{pp}} \right)^{1/3} - 0.64 \right] \cdot 10^{-3}

Symbol	Meaning	Unit
$C_F$	Bare-hull ITTC-57 friction coefficient
$\Delta C_F$	Roughness allowance
$k_s$	Mean apparent hull roughness (AHR)	m
$L_\text{pp}$	Length between perpendiculars	m
$1 + k_2$	Appendage form factor - bulkers 1.10–1.15, Ro-Ro 1.20–1.30, cruise w/ stabilisers up to 1.40
$C_F^\text{eff}$	Effective friction coefficient including roughness and appendages

Source: ITTC - *Recommended Procedures 7.5-02-03-01.4*; Townsin - ITTC community paper on average hull roughness

In short

Add hull-roughness ΔCf and appendage form-factor corrections to the bare-hull ITTC-57 friction coefficient per ITTC-78.

Learn the theory Decarbonization Technologies for Ships