"The steam tug Wattle is historically, socially and technologically significant at the national level as the only small harbour steam tug still surviving in Australia."
Steam Tug Wattle was built as a harbor tug in 1933, a steel ship built to Lloyds scantlings. Forty-four steel angle frames, at 20" (508mm) centres from bow to stern, are clad with riveted steel plate of thicknesses varying between 5/8" (16mm) and 3/8" (10mm).
Steam is supplied from a two-furnace Scotch Marine wet-back boiler, 10'9" (3.28m) diameter and 11'0" (3.35m) long. The boiler was originally fired with dewatered and filtered waste oil, but has recently been converted to burn distillate for environmental and maintenance reasons. Total bunker capacity is 10 tons in port and starboard tanks. The boiler operates at a pressure of 120-130 psi to power a two-cylinder (compound) engine.
The high pressure cylinder is 13.75" (349mm) in diameter and the low pressure cylinder is 31" (787mm) in diameter. The stroke is 20" (508mm). Steam-assisted reversing gear (Stevenson's link) is fitted. The engine turns a four-bladed propeller, 7'6" (2.29m) in diameter with a pitch of 9'4" (2.84m).
The ship is recorded as having achieved 10.8 knots at 132 rpm, 287 IHP, during first trials in light condition (118 tons). (Some records say 9.82 knots at 134 rpm and a boiler pressure of 128 psi). Wattle generally steams at about 8 knots (85-90 rpm).
Seven Auxiliary Steam Engines
- Auxiliary boiler feed pump
- Boiler feed injector
- Fuel oil pumps (two horizontal Worthington pumps)
- Condenser pump
- Dynamo (110 volt, 1.5kW)
- Duplex vertical fire and salvage pump
- Steering engine
Wattle was not originally equipped with a steering engine but the ship was found to be very difficult to steer, so the auxiliary steering engine was fitted on the main deck, abaft the Engine Room skylight. To meet current safety and amenity standards, a 19kVA diesel generator was installed in the aft storage compartment in 2016.
- Length o/a 81'3" (24.76m)
- Breadth moulded 17'6" (5.33m)
- Draft 9'3" (2.82m)
- Gross tonnage 99.8 tons (101.4 tonnes)
Tug Wattle Specifications at October 1933Launched at Cockatoo Island on 27 June 1933 by Cockatoo Docks & Engineering Co. Ltd. (CODECO) on order from the Commonwealth Shipping Board.
Length overall: 80 feet 8 inches
Length: 75 feet
Breadth: 17 feet 3 inches
Moulded depth: 9 feet 3 inches
Speed: 10 knots
Displacement: 120 tons (in modern terms, 132 tonnes light vessel weight)
Bunkers: 4 tons of oil fuel with 2.4 tons of reserve feed
36 hours endurance at 300 IHP = 10 knots = 360 miles
Single screw, compound two cylinder (HP and LP)
Indicated horsepower (IHP) 300 at 134 RPM
Return tubes main type, 2 x Deighton withdrawable furnace – 3 foot diameter x 7 feet 10 inches long. Heating surface 1196 square feet. Boiler 10 feet 6 inches diameter, 11 feet long, Working pressure 130 lbs.
- National Archives of Australia
- S.T Wattle - An Engineering Perspective
- Steam Tug Wattle (G.C. Hogben, Shiplovers Society of Victoria)
- VSA Steam Tug Wattle: a Short History, Capt. R.C. Hope
- Scotch Boilers (Marine Steam Engines)