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PRACTICAL]
963
SHIPBUILDING


purpose they are intended, so that they can be readily identified ' hoisting, except for 'plates under the bottom and counter, where a and removed without loss of time. When required, they are taken wire rope is used. "

from the racks, and the edges, butts and rivet h0les carefully At Newport News, in Virginia, the structures are' differently

  • MRS* “' Enlarged Section through C D.

Enlarged Section through A B. shewing scarfed corner of Plate N.


marked upon them before they are taken to the machines where arranged, being on the cantilever travelling-crane principle. Ther: the shearing, punching, drilling, shaping, &c., are carried out, after are five such structures in the yard; three of them are wood thwlhich they are taken to their proper position in the

In many shipyards great attention has been given

Section shewing Ordinary Type of Plating § ;'§ to the questions of the economical handling of the ¢'2 V, ¢""° cranes material, and very costly and novel appliances, A are to be found in these yards for the pur- pose. s an example mention may be made of the overhead cranes fitted at the Union Ironworks of San Francxacoid A féamlewcilrk of wood is built up over the $€C1lOI1 Sllewlrlg loggled Plating. entire

all directiorislzciorecarryiriegstwrf tiiatifeliliiig Qiiiderrzégneisi reharfe fourhbuilding ble:-ths fitted in this manner, as a engt of 408 ft., a clear breadth of 80 ft., and clear h ' ht' f ft. A ' f

50 ft. spread at eacheieid of t7lfe erectioilwirlicgreraiislelg i(t)s S ' h ' |0 led Frames effective length to 500 ft. Each of the travellinigirders ecuon, S ewmg gg it Cal1@S 21 U0 ey, with moti n tran ve se to the ship; , -~-~ -»— — 1->% . . - . . ., , . . . . e, e§ .f, ,- , , five tons can be s0 lifted, an(i1 partssof ihe ship's struc- ture not exceeding this weight can be taken from the Ef0HCl anywhere in the neighbourhood of the structure and conveyed to any desired spot in the ship. The driving power is electric. The longitudinal travel of the girders IS 180 ft. r minute the transverse travel FIG. 79.-Methods of working Shell-plating. E6; of the trolley I last two of steel. The largest is 700 ft. long. One trestle structure or

and speed of lift, eac 90 ft. per minute. A manila rope is used for gantry, serves two building berths, and runs longitudinally between