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232 THE FIG. 10—TIMBERS LONG ENOUGH TO REQUIRE TWO CARS FREQUENTLY ARE NEEDED IN WOODEN SHIPBUILDING frame construction. As a which is suitable for ship construction, Douglas fir, grown on the Pacific coast, is fully as important as yellow pine, and on account of the exceptionally large size of the trees, and the relative light- ness of the wood, this timber has pe- culiar advantages of its own. Concern- ing this wood, the United States forest service, in Bulletin No. 88, has put itself on record as follows: ~“Douglas fir may perhaps be con- sidered the most important of American woods. Though in point of production it ranks recond to southern yellow pine, its rapid growth in the Pacific coast forests, its comparatively wide distribu- tion and the great variety of uses to which its wood may be put, place it first. As a structural timber it is not surpassed and probably it is most widely used and known in this ca- pacity.” Fir an Important Wood Dougias fir comprises more than 25 per cent of the standing timber supply of the United States, including both hard and soft woods. The _ timber stand of Washington and Oregon - is such as to insure a permanent source of supply of the highest class of lumber for shipbuilding. Also, the winter cli- mate in this vast, western timber-belt is mild, enabling the lumber camps and mills to operate continuously, thereby _ producing a. steady supply of manu- factured products. Practically all log transportation is by water and many of the mills are lo- cated on tidewater, in close proximity to shipbuilding plants. These conditions make it possible to produce lumber for ship construction at a minimum operat- ing cost. Pacific coast logging operators are provided with equipment specially adapted for handling large logs. Under material the ordinary methods of procedure, the logs are hauled out from the places where the trees are felled by steel cables operated by powerful hoisting engines. This operation is termed yarding. The yarded logs are usually rolled onto flat cars or specially con- structed trucks, on which they are hauled to the water, either a river or tidewater. Here they are made up into rafts and towed to the mills. To some mills, of course, the logs are delivered direct by rail. Big Timbers are Cut The mills on .the Pacific coast are equipped with extra heavy facilities for handling big logs and getting out big timbers and heavy planks specially suited to ship construction. Both large circular and band saws are used to work up the logs, while heavy planing mills. are provided to dress the timbers. The modern mills are a!so completely provided with power-driven roller tables | and transfers for handling the lumber during the process of manufacture. The accompanying illustrations show the es- sentials of the logging and lumbering operations on the Pacific coast. Douglas fir trees grow commonly from: 3 to 5 feet in diameter and from 175 to 250 feet high. Tremendous tim- bers, particularly suited to shipbuilding, therefore are available in quantity. Structural timbers of Douglas fir, 18 x 18 inches in section and 120 to 140 feet long, may be obtained from mills at any time, and timbers 36 inches square and 80 or 90 feet long are equally avail- able. By the use of such timbers, the largest boats can be constructed with a minimum of splicing and _ scarfing, which not only reduces labor costs but materially increases the strength or seaworthiness of the vessel. Dougitas fir has an average specific gravity of 0.53 based on its oven dry MARINE REVIEW July, 1917 volume. The specific gravity based on green volume, before shrinkage, is 0.46; based on air-dry volume it is 0.48. The green wood weighs 38 pounds per cubic foot, or 3.166 pounds per board foot and the air-dry wood 34 pounds per cubic foot or 2.836 pounds per board foot. These weights vary in fir as in other woods but the foregoing figures are reliable averages. A knowledge of these figures is indispensable to the naval architect or shipbuilder, in com- puting the weights, trim and displace- ment of his vessel. The method of figuring these weights will be brought out later in this series. Too many wooden ships at the present time are constructed and trimmed by guesswork, resulting in some exceedingly costly ex- periences for the shipowner. Preservatives are Recommended Douglas fir and southern pine are on a par as to durability, although like other woods when used for shipbuild- ing, precautions should be taken at the time the boat is constructed to see that preservatives are effectively applied and that the necessary amount of ventilation is supplied to prevent the collection of moist, stagnant air in any part of the vessel. For preserving the timber, com- mon. salt is frequently introduced be- tween the frame joints and between the frame members and the planking and ceiling. Most modern shipbuilders, however, prefer creosote, carbolineum, or some similar compound applied with a brush or o!d broom to the joints dur- ing the process of construction. On account of differences of opinion recently voired regarding the advisabil- AN FiG. 11—EORING WITH AIR HOLES DRIEE