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: --
|Length over outrigger
|Breadth over all
|Breadth at deck inside
|Breadth at top inside
|Depth over all
|Depth to dock deck
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
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.
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.
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
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.