This series of experiments, requested by the Maritime Board of Self-Defense Force and subsidized by the Ministry of Transportations, was executed, in order to obtain some useful data for designing the wood built hull of such high speed boats as patrol boats, motor torpedo-boats, mine sweepers, etc. Having done the test upon the panel of double planked shell and the model experiments upon the strength of beams having various kinds of constructions as motor torpedo-boats, the authors were able to find several analytical conclusions as follows. (1) Not only the bending deflection but also the shear deformation are indispensable as regards the strength of the wooden hull structure. (2) The double diagonal method is the best way to construct the side shell. (3) The strength of the wooden hull structure is affected by the end fastening of each plank. (4) The phenomena of shear lag, owing to the weak shearing strength, are observed in the stress analysis of the deck plank. (5) The stress of longitudinal members fitted inside frames or beams is not so effective. (6) The panel of glued double diagonal plank in spite of its satisfactory rigidity and strength, has a fault to break suddenly. Finally, the authors insist that the further investigation should be necessary upon the mechanism of fixing nails, bolts and screws and the shear lag in the panel of wooden plank.