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

West July, 1917 loads most satisfactorily, is deduced: “Selected Common is a grade selected from No. 1 Common and shall consist of lumber free from defects that materially impair the strength of the piece, well manufactured and suitable for high class constructional and structural purposes.” Considerable more information might be presented on the strength and _ physi- cal characteristics. of ship timbers, but enough has been included to embrace the fundamental facts, and for more exhaustive data-the reader is referred to civil engineering hand books and to the various special booklets on struc- tural timber, such as that issued by the Coast Lumbermen’s _ association. It might be added, however, that a safe fibre stress for fir or pine, is considered to be from 1600 to 1800 pounds per square inch in tension, 1600 pound's for compression parallel to the grain, and 400 pounds for compression across the grain. The weaknesses introduced by the practice of sawing out the bilge turns in the frame timbers of large ships are indicated by the great varia- tion in the last two sets of figures. How Timbers are Shaped Before going on into the design and construction of ships in detail, it is advisable briefly to consider the methods of shaping and fashioning timbers for ship construction and also the principal methods of fastening the various ele- ments together. The data about to be presented is of a purely general char- acter. More detailed methods of work- ing up timbers and fastenings will be considered later. Generally speaking, timbers are shaped by sawing, chopping, planing and_ bor- ing. As far as possible, in modern wooden. shipyards, machines are sup- planting hand labor for all of these operations. Band saws or jig saws, together with common circular. saws ‘are used for a great variety of operations. Air-driven boring augers are used and THE MARINE REVIEW bits, chisels, and all the tools found in the carpenter’s kit also are utilized. For fastenings, dowels, treenails, drift bolts, spikes and screw bolts are em- ployed. The various pieces may also be scarfed, that is, beveled together, so as to add to the strength of the joint. Treenails are usually 1% inches in diameter and from 26 to 30 inches long. They are made of hard wood, usually 237 fastening the main members of wooden ships together, steel or iron drift-bolts are used. Usually. they are about 1- inch in diameter. They are generally driven by air hammers in holes bored tse-inch smaller in diameter than the bolt. Although the difference between the size of the hole and that of the bolt is small, they hold tenaciously, especially | when the ship is new. It is said that Table IV Average Strength Values for Structural Timbers (Grade 1, Tentative Grading Rules, U. S. Forest Service) : GREEN MATERIAL Results Taken from United States Forest Service Bulletin 108, Page 65, Table 8 Fiber stress at elastic No limit SS HOL per sq. in. Species tests Pounds Douglas dirs. ic 81 4,402 Longleaf pine .... Le 3,734 Loblolly pine .... 45 3,513 Shortleaf pine .... 35 3,318 Western hemlock. ‘ 26 3,689 Western larch’... 45 3,662 aattta bakes ccc ees 9 So, Low Redwood. 3.2..0%... oe 4,031 Norway pine ..... 17 3,082 Relative Relative strength stiffness based on based on Modulus modulus of modulus of Modulus of rupture. _ elasticity. of elasticity Douglas Douglas rupture persq.in. fir=100 fir = 100 per sq. in. 1,000 per cent.: >. per cent: Pounds pounds Per cent Per cent 6,919 1,643 100.0 100.0 6,140 1,463 88.7 89.0 5,898 1,535 85.3 93.4 5,849 15525 84.5 92.8 5,615 1,481 81.1 90.2 5,479 1,365 79.2 83.1 5,469 1,276 79.0 Techs 4,932 1,097 4123 66.8 4,821 1,373 69.6 83.6 locust, and are used chiefly for fasten- ing the planking and ceiling to the frames. For this purpose a hole the scant diameter of the treenail is bored in the members to be fastened and the treenail is driven home with an air hammer. After it is in place, it is cut off, split on the end, and wedged to a tight fit. The subsequent action of the water is supposed to swell the treenail and make it fit tighter. Although treenai!s are used exten- sively in modern shipbuilding, there is doubt as to their efficiency after the ship has had an opportunity to work in a seaway. Undoubtedly, however, they were employed in the construction of we Z FIG. 14—DIVISION OF STRINGER INTO VOLUMES FOR CONSIDERATION OF POSITIONS OF KNOTS—SEE TABLES I AND II special machines have been developed for beveling timbers and _ performing other operations peculiar to shipbuild- ing. In many cases, however, hand tools must be used, as for instance in dubbing-off the inside of the hull pre- paratory to laying the ceiling. For many operations such as this, the adz is indispensable. For rough hewing, axes are employed, while hand planes, the ark, for want of knowledge of more modern fastenings, and this is a sufficient recommendation for their con- tinued use in the eyes of many old- line shipbuilders. The chief virtue of treenails seems to lie in the fact that they work with the ship, and therefore do not present as unyielding a resist- ance as a steel fastening. To supplement treenails, however, in drift-bolts driven 3 feet into a fir tim- ber hold so fast that they break in ten- sion before they pull out. Wherever possible such bolts are driven through: and clenched on steel rings in the in- side. For “sticking” the planking to the frames and other preliminary fastenings, as well as for securing the deck planks, galvanized standard ship spikes are used. Usually they are 72-inch square and 8 or 10 inches long. Screw bolts also are used for some forms of fasten- ings, as well as bolts fitted with wash- ers and nuts. The latter may be taken up from time to time as required. : Tests of Spikes Some tests of spikes were made at the Seattle testing laboratory of -the United States forest service recently, from which the following conclusions were drawn: 1—The form of the point of the common _spike is such that it inclines not to follow the hole. : 2—If the holes are not too large and the spikes follow the holes closely, the re- sistance to withdrawal usually will be in- creased. 3—If spikes do not follow the holes, the resistance to withdrawal may be greatly re- duced. : '4_Spikes not into lowered. In modern wooden vessels built on the coasts of the United States, con- siderable use is made of edge-bolting to fasten the various keel and keelson ele- ments. and the strakes of ceiling to- (Concluded on page 257) holes, but resistance to the their driven close them, will have