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310 THe /AaRINE REVIEW September, 1909 Floating Dry Dock for the Oregon Dry N 1903, the Port of Portland Com- mission built a 10,000-ton sectional floating dry dock for Portland har- bor. In 1907, only five of the vessels docked on this dock registered over 2,000 tons gross. In 1908, there were only six vessels of 2,000 tons gross or over docked. On the other hand, in 1907, 69 per cent, and in 1908, 68 per cent of the total dockages were Dock Co. 300 ft. in length, 40 ft. beam and 18 ft. draught and that could take care of average saiing ships, of which a large number visit Portland annually. The dead weight of steamers of the size mentioned varies between 2,500 and 3,- 000 tons, while very tew sailing vessels exceed 300 ft. in length or 2,000 tons dead weight. It was therefore de- cided to build a dock 286 ft. in length on the pontoon and 348 ft. over the tion has a molded depth at the center of 10 ft. and at the sides of 9 ft, 1 in. The total height of wing walls is 37 ft. 6 in. The single pontoon is 286 ft. long, 76 ft. 8 in. extreme beam and, as already noted, 10 ft. deep at center. It was not necessary to pro- vide for self-docking as, if required, the whole structure may be docked in the large dock belonging to the Port of Portland, which is public property New Froatinc Dry Dock or THE Oregon Dry Dock Co. PARED WITH AN ORDINARY STERN WHEEL River STEAMER. vessels under 1,000 tons gross. In view of this and of the well known fact that small vessels can be more quickly and economical'y handled in a_ small than in a large dock, the Oregon Dry Dock Co. was organized last year to build a medium size modern floating dry dock, particularly adapted to this class of ship, and Fred A, Ballin, naval architect of Portland, was commis- sioned to design a dock to mect these conditions. We are indebted to Mr. Ballin for the drawings and details of construction which are presented here- with, Conditions demanded a dock that would safely handle any vessel up to TuIs EXTERIOR VIEW aprons, with a clear width on deck of 96 ft. and at the top sides of 64 ft. After a thorough study of the local conditions, a wooden dock was decided upon, because on the west coast the cost of steel construction as compared with wood is so high that the steel dock would be considerably more ex- pensive, even taking into consideration its longer life. Furthermore, experi- ence has shown that the pontoons of wooden docks which have been in service as long as 50 years are still sound and in good condition, although the wings usually decay much more rapidly, as is to be expected. The pontoon of the dock under considera- SHOWS THE SizE OF THE Dock as Com- and open to the use of anyone on payment of the regular rates. This consequent'y simplified the design and made a sectional dock unnecessary. At 32 ft. draught, which will accom- modate ships drawing 18 ft, allowing 4 ft. for keel blocks, the placement of the dock is 10,170 tons. The net displacement and buoy- ancy is 7,640 net tons. With the deck of the pontoon just out of water, the maximum lifting capacity is 3,000 tons. The unsubmerged dead weight amounts to about 3,000 tons, having a -sub- nferged buoyancy of about 640 tons, requiring about 500 tons of ballast and machinery to balance the dock at 32 dis- net gross