Dr Yasushi Yoshida from International Boat Research, Japan, presented a lecture on "Scale Effects Related to the Resistance of Planning Boats". He is at present a Visiting Research Fellow at Wessex Institute of Technology for a one-year period and is currently researching into hydrodynamic problems.
The lecture was concerned with the balance between the thrust and resistance of planning boats travelling at maximum speed. Trial test data was available for a PT of 35m overall, 9m width and a displacement of 1304.3 kN (133 tonf). The craft, which has three propellers, produced a thrust of 184 kN (18.8 tonf) that slightly exceeded the total resistance at the maximum speed of 41.19 knots. A greater difference between the thrust and resistance is evident at decreasing speed. This validates Attwood's findings in his book 'Textbook of Theoretical Naval Architecture' which indicates that an overestimation of thrust by 10% is necessary when there is no design information. An analysis of the propeller performance was obtained by nomogram based on Gawn's test data on propellers and the resistance was found by empirical equations based on towing tank test data using models of 2.5m in length.
Dr Yoshida will be presenting a paper based on this topic at the Marine Technology Conference, to be held in Szczecin, Poland from 28-30 May, 2003.
Wessex Institute