Floating Dry Dock and Repair Plant for Toronto

The Dominion Government recently granted Polson Iron Works, Ltd., Toronto, a 3% bonus yearly for 20 years on $900,000 to be spent in building a floating dry dock and a repair plant at Toronto. The dock will be located at the foot of Frederick St., just west of and adjoining the company's present plant. The company has leased from the city, 136 ft. of land just west of the present property on which a basin will be blasted to a depth of 28 ft. to accommodate the floating dock. The company has also recently acquired the property to the east of its present plant and to the east of the Sherbourne St. slip, and it is the intention to use this property outside of Lake St., as a basin for the accommodation of steam boats which may come to the dock for repairs, and this space will provide ample dock accommodation for all vessels which may be waiting their turn to use the dock.

The floating dry dock is ultimately to be of the following dimensions: --

At present, two sections 150 by 100 ft. are being built, making an overall length of 336 ft., having a lifting capacity of 4,500 tons, and easily able to accommodate any vessel on Lake Ontario. In the future, when larger vessels are expected to be on these waters, a 300 ft. section will be built and added to the dock, making a total length of 642 ft., and having a lifting capacity of 9000 tons.

The dry dock is of the U-shaped section, and each 150 ft. part is divided transversely by two watertight bulkheads, spaced 50 ft. apart. These bulkheads are fitted intercostally between the three longitudinal bulkheads which are run continuously from end to end, the centre one being non-watertight, and the side ones at 2 ft. from the centre line being watertight. These bulkheads are composed of 3/8 in. plating, 5 by 3 by 3/8 in. vertical stiffeners, spaced 30 in. apart and 5 in. by 3 by 3/8 in. horizontal stiffeners spaced about 7 ft. apart, and shell and deck angles of 3 l/2 by 3 1/2 by 3/8 in.

The framing consists of both longitudinal and transverse systems, the former being carried out between the wing bulkheads in the centre and the latter outside the wing bulkheads and on the walls. Solid floors are fitted transversely every 10 ft. between the longitudinal bulkheads, and consist of 3/8 in. plating, with connecting angles of 3 by 3 by 3/8 in. and vertical stiffeners of 5 by 3 by 3/8 in. spaced 30 ins. apart. Between these solid floors are fitted the longitudinal frames which are 6 by 3 1/2 by 3/8 in. on the bottom and 12 by 25 in. channel at the top. The former are fitted intercostally between the solid floors, but the latter run continuously from bulkhead to bulkhead. This longitudinal system of framing is completed by a continuous series of lattice work of 4 by 4 by 3/8 in. angles with 3/8 in. cross ties and brackets securely connecting them to frames and vertical stiffeners. The longitudinal framing amounts to a non-watertight centre bulkhead, two side wing bulkheads, both watertight, and 14 rows of frames and bracings. The transverse framing consists of a series of lattice work frames opposite every solid floor of 6 by 3 1/2 by 3/8 in. angle frames, 3/8 in. brackets and 4 by 4 by 3/8 in. bracings. The side frames of outer and inner walls extend from top to bottom continuously, and have beams securely bracketed to them about every 7 ft. The intermediate frames are fitted between each solid floor, spaced 30 in. and extend from wing bulkhead to top and are of 6 by 3 1/2 by 3/8 in. angles with 3/8 in. brackets connecting beams and stanchions.

The bottom plating is 7-16 in. worked transversely in way of longitudinal framing at centre, and longitudinally in way of transverse framing at sides. The outer wall is 3/8 in. plating with top and bottom strakes of 7-16 in. The inside wall is of 3/8 in. plating and the top is 7-16. The deck plating is 3/8 in., worked in the same manner as the bottom plating in connection with the framing. The corner angles at the deck, top and bilge are 4 by 4 1/2 in. All shell landings will be joggled and linears dispensed with. The end plating is 3/8 in., and is connected to deck and bottom by 4 by 4 1/2 in. angles with 5 by 3 by 3/8 ins. vertical stiffeners spaced 30 ins. and horizontal stiffeners of 5 by 3 by 3/8 ins. The gangways are fitted in each section in each side; the opening being 20 by 15 ft., with plating 3/8 in., and connecting angles 3 by 3 by 3/8 in. The rivets in the whole construction are 3/4 in. in diameter, the plate landings being double rivetted and the laps quadruple rivitted.

Ladders are placed at each side of each pontoon and rails and stanchions are fitted all around the top. Cast iron bollards are placed in each corner of each section and securely bolted into place. Three cast steel brackets are placed on each side of each section securely fastened to heavy brackets and special connection between the two sections are fitted so as to give rigidity to the whole dock when lifting operations are under way.

The connecting links are made of forged iron and secured by bolts and held by strong lugs. The outrigger platform which extends 15 ft. from each end of dock is made up of 3/8 in. plating and has brackets and stays every 30 ft. with a fender all round its edge. On the top deck, two manholes with hinged covers are fitted to each watertight compartment. Ladders of 2 1/2 by 1/2 in. flat, are placed in way of each manhole on the bulkheads.

Bilge and keel blocks are placed at suitable distances apart having an oak base 60 ft. long on which the bilge blocks can slide. This base will be bolted through clips 5 by 3 by 3/8 in. securely riveted to deck. The sliding blocks are of pine and the best arrangement of guides, pulleys, and chains will be fitted so as to make the work of docking as easy as possible.

[p. 979] The pumps are the horizontal centrifugal type with 16 in. suction located in the bottom of the dock and are driven by a vertical shaft connected to a 50 h.p. motor, located on top of dock. Two pumps are fitted in each section and all parts are interchangeable. The pumps have a capacity of 7,000 imperial gallons a minute at 300 revolutions. The two pumps in each section are to empty that section in about 1 hour, 20 minutes. The motors are 50 h.p., located on suitable base plate at top of dock. The pumps are located in the bottom of the docks, discharging through the side of the dock about 3 ft. above the bottom. The casing is of cast iron and about 7 fl. in diameter.

The suction nozzle is 16 ins. in diameter and the discharge 15 ins. diameter, the latter having a 15 in. screw check valve between end and sea valve. A cast iron manifold is fitted close to each pump for the end compartments, and two similar manifolds for the middle compartments, and from these the different branch lines run. The branches to the centre compartment are 6 in. and to the wing compartments 10 ins., each valve being fitted with a quick opening gate valve close to the manifold. Suction boxes are fitted on end of each pipe and placed in a gutterway of special construction built in the bottom of the dock, so that it can be drained dry. A 16 in. pipe connects the two pumps so that one pump can operate the whole section in case of emergency. The two Hooding valves are 18 ins. in diameter. The flooding and discharge valves are operated by a spindle, with hand wheel on stand, with different heights of stands so as to be easily distinguished.

As previously stated, it is expected that at a future date, a 300 ft. section will be added to the first 300 ft. dry dock, and so accommodate the largest vessels that are expected to be on these waters, but in case of the smaller vessels, up to 150 ft., the sections will be separated and only one used for lifting. In operating docks of this description, considerable care has to be taken previous to the submersion of the dock, particularly with regard to the position of the bilge blocks, which should be as far away from the centre as possible. Also all chains and guides must be seen to be clear of all obstructions. At the corners of the dock are vertical rollers which are of great assistance to the vessel if she is being docked in bad weather, and should they be struck by the vessel, instead of doing the damage that a square corner might do, they assist rather than retard her headway. The dock will be usually sunk about 2 ft. deeper than the draft of the vessel to be raised, and after the vessel has been securely moored by ranging lines fore and aft and by mechanically governed side shores, the pumping operations will be begun and the dock and vessel raised.

The dock will have a complete installation of electric light on the top deck, and every convenience for the rapid handling of all kinds of repairs.

It is expected to have the two sections now under construction completed so that vessels may be docked on the opening of navigation.

The company is also building a new boiler shop 300 by 120 ft, composed entirely of steel, except the boiler walls. Two large compartments are to be built, one 60 by 40 ft., for a pump and compressor room, the other 60 by 60 ft., for a flange fire shop.