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September, 1913 THE MARINE REVIEW Countersunk Wood Scre| Holes 46 Dia, & bes . i a | 3 : 3 EL Sy Centre of Car oe i Fug.8 ' Fig9 g 5 ee 3 & / S ae J 5 el "| s etd es S- Centre of Carr SHAPE OF CAM FOR CARGO BOAT 35045 'x 27' AT 22' DRAUGHT | Fig. il SHAPE OF CAM FOR EQUILATERAL TRIAN- BET GULAR PRISM, FLOATING WITH VERTEX (9527. 0.) DOWNWARDS AT 50% TOTAL DISPLACEMENT CURVES OF DECLINING ANGLES SHAPE OF CAM FOR A RECTANGULAR PRISM OF BREADTH =TWICE DEPTH, AT _ 50% DISPLACEMENT. PARTICULARS OF MODEL. NoFreeWater Brake Blocks Not Touching eran Loven enes: 99 sroesnemomes Serene cearon ae et Wp a: po eee oe » -- Not Toue " DO aoe joe »-- Louc Not Touchi SSOONDMAWN~ MAT ee Degrees of Toll. { O- 85 80.95. YO 65 60 3550 3527.F) 'disposal. I accordingly submitted it as one part of a proposed scheme of re- search work, and the results of this study, so far as it has gone, constitute the subject of this paper. 7. Before entering upon this em- perimental work, I investigated the statical effects of loose water in ships. This formed the subject of a paper that I had the honor of submitting to this institution last year. It was in- _ tended as a preliminary to the deter- mination of the dynamical effects when rolling amongst waves. 8. The machine that has been used for these experiments is in many ways unique, and is the only one of its kind in existence in this country. The prin- ciples. underlying its design were Pointed out to this institution in 1900 by Colonel (then Captain) Russo, R. I. N., in his paper. on the navipendu- lum; and also in 1902, when he gave the results of an experimental study of the rolling of ships amongst waves 'Obtained by his apparatus. As, how- FS 40 3S Namber of Rolls. . ever, there are several new features in connection with the machine at Glas- gow,. it may be as well to give a brief description of it and the theory under- lying its design. 9 AB and CD (fig. £) are. two radii that revolve about A and C re- Fig.10. Locus OF Z FOR CARGO BOAT 182k27% 13'.5" AT 5:9" DRAUGHT AND 600TONS DISPLACEMENT KG=3:8 FEET. | | | | @se7. spectively, and are always parallel to each other. AC is a vertical line. A rod E is pivoted at B to AB, and can slide through a sleeve D_ that is piv- nted to Oo nes, JF. the values of r, and rz are correctly chosen, and AB and CD are revolved at a particular uniform speed, B will represent the J58 orbit circle of a trochoidal wave of height 27, and BD will always lie in the direction of the normal to the wave slope at B. Thus the resultant force on any particle at B will, at this speed of rotation, always act along DB. 10. The lengths of 7, and re and the speed of rotation may be obtained as follows: Let the machine represent a wave at 1 a scale of --th the full size. Let ] be n the length of the actual wave and h its height. Then-- h i 2n Ro eRea@ V4 ne To or 1,4 R= T1--1s and, therefore, if 7, 72 and d are fixed quantities, R is constant; that is, AC and BD always meet in the same. point QO. Fhus, if we make 7% OF Slch @ length that R is equal to the radius of the rolling circle of a trochoid of length J, and rotate the machine at the appropriate revolutions, BD _ will always represent. the normal to the wave surface; as it iS a property of the trochoidal wave that the line join- ing any point of its surface to a point vertically above its orbit center at a distance equal to the radius of the rolling circle is a normal to the surface at that point. Now-- R=-- 271 d Gt, (:--- ae h 2r nd i 2 (:- 2n 1 The period of a wave length J is-- 2h ? g and therefore the period of the ma- chine will be-- and-- 271 --_--_-- . gn So that, in order to represent a wave of length / and height h, we make-- e h Piao rs 2n : h 2nd : noo (:- 2n l and rotate the machine at such a speed that its period is-- Zat --_---- . gn