Wetted Surface - Mumford Formula

Wetted-surface estimate for displacement hulls from LWL, T and displacement. Used for quick resistance estimates when offsets are unavailable.

ResistanceWetted surface

Waterline lengthmDraftmDisplacement volume ∇m³

Wetted surface area S: 8,285m²

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

S = 1.7 \cdot L \cdot T + \frac{\nabla}{T}

Symbol	Meaning	Unit
$L$	Waterline length	m
$T$	Draft	m
$\nabla$	Displacement volume	m³
$S$	Wetted surface	m²

Source: Mumford quoted in SNAME PNA Vol II Ch.5

In short

Wetted-surface estimate for displacement hulls from LWL, T and displacement.

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