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Hull Efficiency η_H

η_H = (1 − t) / (1 − w). Usually 1.05–1.15 for single-screw full-form hulls - the wake gain outweighs thrust deduction.

Propulsion
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Formula, assumptions, and limits

ηH=1t1w\eta_H = \frac{1 - t}{1 - w}
SymbolMeaningUnit
ttThrust deduction fraction
wwTaylor wake fraction
ηH\eta_HHull efficiency

Source: Harvald - Resistance and Propulsion of Ships

In short

\u03b7_H = (1 \u2212 t) / (1 \u2212 w).

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