Power by Admiralty Coefficient
Estimate a ship's propulsive power by the Admiralty formula, P = (∆^(2/3)·V³)/C, from the displacement (∆, t), the speed (V, knots) and the Admiralty coefficient (C), characteristic of similar hulls. It is a classic, fast method to predict the required power in the preliminary design stage, based on similarity with existing ships. The V³ dependence shows the high cost of speed. Enter the displacement, the speed and the coefficient C.
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Potência pelo coeficiente do Almirantado
Antes dos métodos computacionais, os projetistas navais estimavam a potência de um navio novo por semelhança com navios existentes, usando a fórmula do Almirantado: P = (∆^(2/3)·V³)/C. O coeficiente C é quase constante para cascos parecidos, então, conhecendo-o de um navio de referência, prevê-se a potência do projeto. Dois detalhes contam a física: o expoente 2/3 no deslocamento converte volume em área (a resistência escala com a superfície molhada), e o cubo da velocidade revela o custo brutal de ir mais rápido — dobrar a velocidade exige oito vezes mais potência. Continua útil hoje como estimativa rápida de anteprojeto. Informe o deslocamento, a velocidade e o coeficiente C.
Related Tools
Prismatic Coefficient (Cp)
Compute a hull's prismatic coefficient (Cp), Cp = ∇/(Am·L), the ratio of the displaced volume to that of a prism with the midship section area (Am) along the whole length. It indicates how volume is distributed lengthwise: a low Cp concentrates volume amidships (good for low speeds), a high Cp pushes it to the ends (better at high speeds). It is decisive in resistance design. Enter the displaced volume, the midship section area and the length.
Block Coefficient (Cb)
Compute a ship's block coefficient (Cb), Cb = ∇/(L·B·T), the ratio of the displaced (carene) volume to the enclosing box (length × beam × draft). It measures how 'full' the hull is: slow cargo ships have a high Cb (~0.8); fast, fine vessels a low Cb (~0.5). It is one of the central parameters of naval architecture. Enter the displaced volume, the length, the beam and the draft.
Propeller (Propulsive) Efficiency
Compute a propeller's propulsive efficiency, η = (T·V/P)·100%, the ratio of useful propulsion power (thrust × speed) to the power delivered to the shaft. It measures how much of the engine power the propeller converts into forward thrust — well-designed propellers reach 80–88% in cruise. It drops sharply at low speed (takeoff) and near the speed of sound at the blade tips. Enter the thrust, the speed and the shaft power.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.