Question

2) A boat of mass 2500 kg has two hydrofoils, each of chord 30 cm and span 1.5 meters, with CL,max-1.2 and CD0-0.08. Its engine can deliver 130 kW to the water. For seawater at 20°C, estimate (a) the minimum speed for which the foils support the boat and (b) the maximum speed attainable

Answer 1

Find Total platform area, 2b 2×0.3 m 1.5 m 0.9 m2 Find Aspect ratio 1.5 m 0.3 m Find Minimum speed, 2W 2x 2500 kg×9.81 m/s 1025 kg/m x1.2x0.9 m - p,ttl = 6.66 m/s Lift to drag force ratio: F C Fan CD CD CD Life coefficient, 2W 2mg 2x 2500x9.81 1025x0.9 53.2 From equation (1) 53.2 CD = 0.08 + = 0.084 180 The engine can deliver Power to the water, to find the maximum speed attainable 1801 V*)2 1801 アー×1025× 0.9V3 96900=| 0.08 + -2627P + 2250 0 13.5m/s