A 2-ft-long model of a ship is tested in a freshwater tow tank. The measured drag may be split into “friction” drag (Reynolds scaling) and “wave” drag (Froude scaling). The model data are as follows:
Tow speed, ft/s: 0.8 1.6 2.4 3.2 4. 0 4. 8
Friction drag, lbf: 0.016 0.057 0.122 0.208 0.315 0.441
Wave drag, lbf: 0.002 0.021 0.083 0.253 0.509 0.697
The prototype ship is 150 ft long. Estimate its total drag when cruising at 15 kn in seawater at 20°C.