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\ / \\X 2 Ge < ESSSSSS S = Vv) / /ooden This Article, Second in a Series Covering Wooden Shisbudding. rat duilt—Hl a aw Discusses the Strength and Characteristics of Ship Timbers lay down or build a wooden ship, the architect, yard super- intendent and others responsible for the success of the proposed vessel, should acquire a fundamental knowledge of the physical characteristics and strength of the timbers that. will be used in the construction of the hull. An in- vestigation also should be made into the different methods of fastening timbers together in shipbuilding and of the efficiency of such fastenings. In other words, a little knowledge of .the ele- ments of structural engineering is as essential to the shipbuilder as it is to the building contractor or _ bridge erector. For an_ intelligent and thorough grasp of the subject it is necessary, in fact, to start with the lumber industry, which bears the same_ relation § to wooden shipbuilding as iron-ore mining does to the manufacture of steel. In this article, therefore, a few facts will be presented regarding the production of lumber in the United States, to- gether with data on the physical char- acteristics and strength of various species of ship timbers. In the preceding article, figures cov- ering the supply of merchantable timber in the United States and Canada were Bis « any attempt is made to presented. -:To ‘give ah idea, “Of. “the ability of lumber manufacturers to fur- nish ship timbers in quantity, it may be stated that the United States forest ser- vice has estimated the lumber produc- tion of the United States in 1915, the latest year for which figures are avail- able, at 37,013,294,000 board feet. Dur- ing 1915 there were 29,941 mills in ope- ration. The details of the lumber cut of 1915, showing the number of mills and production of each state are given in Table III. By an inspection of this table, it is possible to estimate the pro- duction of the two principal kinds of ship lumber, namely, Douglas fir and southern yellow pine. The pine grow- ing states turned out 17,010,000,000 feet and the fir states, 5,640,000,000 feet in 1915. In 1916, the production of the fir states was approximately 7,000,000,000 feet. About 25 per cent of the Pacific coast cut is available for ship work. In other words, as far as lumber supply is concerned, the Pacific coast mills alone can turn out sufficient material for one thousand 3000-ton ships in a year and the southern mills, because of the smaller size of pine timbers, enough for 1800 to 2000 more. Southern yellow pine is the most abundant of all ship materials, and on account of its wide geographical dis- By H. Cole Estep tribution, comparatively close to the great eastern centers of population, it is extensively employed in building wooden vessel of all kinds. It comes in sufficiently large sizes so that the prin- cipal elements of the ship’s structure, such as the frames, planking and ceil- ing can be worked up in a compara- tively few pieces, without the necessity of resorting to an abnormal number of butts and scarfs. Yellow pine is an even grained, easily worked, dense wood with superior physical characteristics. Detailed figures on the strength of pine timbers are given in Tables I; II and IV. Pine is an unusually durable wood, even when subjected to long continued stresses in a ship’s structure. In the tables just referred to, the modulus of rupture, or breaking strength, of south- ern pine is given as varying from 6437 to 5948 pounds per square inch for the green material and 7033 to 5957 pounds for air-seasoned timber. The weight per cubic foot varies from 38.6 to 31.4 pounds. Ships constructed of southern pine along the Atlantic and gulf coasts have a_ special strength advantage, in that, up to date, natural crooks have been used for the curved frame mem- bers in nearly all cases. Such timbers are appreciably stronger than the sawed FIG. 8-FASHIONING SHIP TIMBERS ON A BAND SAW FIG. 9—SPECIAL MACHINES HAVE BEEN DESIGNED FOR BEVELING AND EDGING TIMBERS 231