The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

36 Fig. Zo. S.S. 340% 45.6 27:3 & 34. 3- age eee 2 THE Marine REVIEW Fig. 2a. Ss. S. 350'X50 X 26.3 & 33.6. 'ce WOT 2 0.088 which are fitted under the upper deck are structural necessities has remained undisturbed in practice. The large iron steamer for passen- gers and cargo even forty years ago was quite commonly of about 400 ft. in length, although some _ seventy years ago the largest iron steamer | Fig. 25 S.S. 3850'X50' X 25.3" & 32. 3. 1907. Pees ec ee ee ee a we ew eee ww we me ee a oe _ a es ae erp vE ; afloat was only 185 ft. long, and, 'as was to be expected, the design of the earlier iron structures was closely al- lied to that of contemporary wood ships. The frame spacing rarely ex- ceeded 18 in. the bilge plating was often 25 per cent heavier, while the sides were usually thinner than the > Fig: 26. PRIESTMANS SELF TRIMMER, S.S. UNIVERSE. i898. DIM$ 300x 42'.4"% 22.4" % 28.4" . oo is , ane---- oN 'four tiers of beams, bottom plating. Fig. 7 (Plate 1.) shows an example of the ordinary type of large passenger and cargo steamer of some thirty years ago, | many of which are. still running, where the weather deck had light © stringer and tie plates in association -- with light topside plating and a nar- row sheer strake doubling, | there were the second and third of which were plated, and the hold space was filled with great keel. sons standing inside the framing, So far as I know, all the existing vessels of this type had the weather deck completely plated not long-after con- struction. Fig. 8 shows the Buenos Ayrean, built by Messrs. Denny in 1879 for the Allan line, the first steel steamer for Transatlantic service--a vessel which marks an epoch, although it only shows a structural design similar in principle to the previous case, ad- vanced to the extent of having only three decks and web frames in the hold in association with a double bot- tom, and a general reduction in scant- lings-.on account of the superior ma- terial. The double bottom construc- tion on this séction, with its excessive longitudinal material, cost, and diffi- culty of construction, provokes a ref- erence to the crooked way in which such developments always seem to work; the first double bottom was simply a series of iron tanks laid on top of the ordinary floors, the next and obvious step was to rivet girders on top of the floors, plate them over, and fit watertight chocks round the frames--the Macintyre tank--then came the common adoption of the various designs, such as that on the Buenos Ayrean, where the double bot- tom was made part of the structural design; and by the time this stage had been reached everyone seemed to have forgotten that in the sizes of ships commonly built a double bot- tom provides greater bottom strength . than is needed for the structure asa whole, or than is provided with the ordinary floor construction. It cannot be said that the introduc- tion of steel revolutionized shipbuild- ing, although it pushed progress fast- er, nor that the manufacturer has been ahead of the*consumer, although there have been great developments since the days of the Buenos Ayream in the number of sections and sizes" of material available. In fact, it was not until the standards committee took up the work two years ago that any attempt was made in Britain t0 systematize the form of steel sections, or to obtain reasonable proportions of web, flange, etc., to depth of sec