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October, 1925 method gives a little added strength, permits the construction to be car- ried unbroken throughout the entire cross section of the hull, and the various degrees of are to which the corner channels-can be curved, per- mits of any desired beam or depth of hull. Another outstanding advantage of this system is that the flanges of the channels can be either bolted or riv- MARINE REVIEW 500 TONS HOPPER BOTTOM SAND BARGE—116 FEET LONG BY 22 FEET BEAM BY 10 FEET 6 INCHES DEEP. CONSTRUCTED OF ALTERNATE STRAKES OF 12 INCHES STEEL CHANNELS AND 6 INCHES YELLOW PINE eted together. It has been desirable, particularly in small hulls, to use bolts to tie the flanges together, because it can be done more cheaply than rivet- ing, as unskilled labor can be used, and no expensive equipment is re- quired. Bolting is also desirable when a small hull is to be fabricated and shipped knocked down into remote re- gions. The bolts are also an advan- tage, if an owner desires to construct such a hull himself, in a minimum amount of time and expense. All four of the hulls constructed to date have the channel flanges bolted to- gether. The bolt spacing in the first hull constructed was 8 inches between cen- ters and on the last three hulls 6 inches between centers. As compared with a riveted job where the pitch is generally 3% diameters there is prac- tically only one-half the amount of punching and bolting in this system. However, in large hulls rivets will be used, and the pitch will be governed by the type of hull, and the work 363 500-TON HOPPER SAND BARGE SUPPORT- ED ON END BLOCKS 95 FEET APART WITHOUT SIGNS OF DEFLECTION OR STRAIN A the vessel is expected to perform. Considerable experimental work has been carried out by the company in perfecting the seams, formed by the channel flanges. Flanges and seams have been set up in many ways: steel against steel, and, with wood, tar paper, cotton felt and other non- metallic fillers between the flanges. The best results were obtained by us- ing a thin strip of cotton felt in the seams, and this method will be carried out in all new construction work. Tar paper also showed up well be- tween the seams, but it did not have as much resiliency as the cotton felt. As tar paper is used extensively in modern plate vessel construction, it can be used equally as well in the channel system. In fact all the four hulls completed have the strip of cotton felt filler in the seams between faying surfaces. The reasons why this method was chosen may be enu- merated at follows: The flanges of the channels do not run smooth and even, and there is considerable roughness on the faying LEFT—CHANNEL CONSTRUCTION OF SIDES, BOTTOM AND FRAME TRUSSING AT FRAMES. 9 FEET SPACING WITH NO INTERMEDIATE RIGHT—INSIDE END VIEW U. S. ENGINEERS LIGHTER, SHOWING METHOD OF CONNECTING SIDE TO BOTTOM AND END WITH NO RIVETS THROUGH OUTER SHELL