Hull Roughness ΔCf (Townsin)

Increment of skin-friction coefficient from measured hull roughness (AHR) using the ITTC-78 Townsin formulation.

HullFriction

Average hull roughnessµmWaterline lengthm

ΔCf: 0.00036 -

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Formula, assumptions, and limits

\Delta C_F = \left[ 110 \cdot \left(\frac{AHR}{L}\right)^{1/3} - 0.64 \right] \cdot 10^{-3}

Symbol	Meaning	Unit
$AHR$	Average hull roughness	µm
$L$	Waterline length	m
$\Delta C_F$	Skin-friction roughness increment

Source: Townsin - Paint roughness

In short

Increment of skin-friction coefficient from measured hull roughness (AHR) using the ITTC-78 Townsin formulation.

Learn the theory Marine Cathodic Protection and Hull Coatings