This paper describes some experimental results on sinkage and trim for Wigley geosim models in the 17th ITTC cooperative works and discusses the analytical prediction by means of duoble model flow assumption, linearized wave resistance theory and boundary layer theory. Futher the sinkage of model is evaluated by using pressure measurements on the hull surface. The results of investigations are obtained as follows; (1) Scale effect is not recognized in measured values of sinkage and trim in towing condition for geosim models, and the scattering of measured date of sinkage is considered to be the effect of seiche in the tank. (2) Sinkage at low speeds is roughly estimated on the assumption of double model flow, however, sinkage and trim are influenced by free waves as Froude number is increased and behavior of sinkage and rim is closely related to wave making resistance. (3) From the evaluation of sinkage by using the pressure measurements on the hull surface, it is found that the sinkage is predominently caused by the pressure depression around the hull. Viscous effect on sinkage and trim is discussed through the boundary layer theory, however the viscous effect is very small.
