A tugboat or tug is a marine vessel that manoeuvres other vessels by pushing or pulling them, with direct contact or a tow line. These boats typically tug ships in circumstances where they cannot or should not move under their own power, such as in crowded harbors or narrow canals , or cannot move at all, such as barges , disabled ships, log rafts , or oil platforms . Some are ocean-going, and some are icebreakers or salvage tugs . Early models were powered by steam engines , which were later superseded by diesel engines . Many have deluge gun water jets, which help in firefighting , especially in harbours.
31-679: The William Rest was a tugboat built for the Toronto Harbour Commission in 1961 for $ 150,000 CAD . She was built in Erieau , Ontario by the Erieau Shipbuilding and Drydock Limited. She displaced 61 gross tons . She was named after the commission's recently deceased director of planning. Rest had worked for the Commission for 46 years. She was powered by a Caterpillar 379D which could supply 560 horsepower (420 kW). In 1975
62-447: A × V a 2 × A a {\displaystyle R_{A}={\frac {1}{2}}\times C_{A}\times \rho _{a}\times V_{a}^{2}\times A_{a}} Where: Values for bollard pull can be determined in two ways. This method is useful for one-off ship designs and smaller shipyards . It is limited in precision - a number of boundary conditions need to be observed to obtain reliable results. Summarizing
93-573: A flat front or bow to line up with the rectangular stern of the barge, often with large pushing knees. The first tugboat, Charlotte Dundas , was built by William Symington in 1801. It had a steam engine and paddle wheels and was used on rivers in Scotland. Paddle tugs proliferated thereafter and were a common sight for a century. In the 1870s schooner hulls were converted to screw tugs. Compound steam engines and scotch boilers provided 300 Indicated Horse Power. Steam tugs were put to use in every harbour of
124-480: A free propeller stream. Like the horsepower or mileage rating of a car, it is a convenient but idealized number that must be adjusted for operating conditions that differ from the test. The bollard pull of a vessel may be reported as two numbers, the static or maximum bollard pull – the highest force measured – and the steady or continuous bollard pull, the average of measurements over an interval of, for example, 10 minutes. An equivalent measurement on land
155-665: A port in Hamburg. On a weekend in May, eight tugboats perform choreographed movements for about an hour to the tunes of waltz and other sorts of dance music. The Tugboat Roundup is a gathering of tugboats and other vessels in celebration of maritime industry. The Waterford Tugboat Roundup is held in the late summer at the confluence of the Hudson and Mohawk Rivers in Waterford, New York. The tugs featured are river tugs and other tugs re-purposed to serve on
186-413: A ship design are costly. Hence, this method makes sense for larger shipyards and for the design of a series of ships. Both methods can be combined. Practical trials can be used to validate the result of numerical simulation. Practical bollard pull tests under simplified conditions are conducted for human powered vehicles . There, bollard pull is often a category in competitions and gives an indication of
217-423: Is a conventional measure of the pulling (or towing) power of a watercraft . It is defined as the force (usually in tonnes -force or kilonewtons (kN)) exerted by a vessel under full power, on a shore-mounted bollard through a tow-line, commonly measured in a practical test (but sometimes simulated) under test conditions that include calm water, no tide , level trim, and sufficient depth and side clearance for
248-467: Is a sturdy cylindrical structure around a special propeller having minimum clearance between the propeller blades and the inner wall of the Kort nozzle. The thrust-to-power ratio is enhanced because the water approaches the propeller in a linear configuration and exits the nozzle the same way. The Kort nozzle is named after its inventor, but many brands exist. The cycloidal propeller is a circular plate mounted on
279-558: Is a tugboat in the animated series South Park . He appears in the episode " The New Terrance and Phillip Movie Trailer " as a sidekick for Russell Crowe in a fictitious television series entitled Fightin' Round The World with Russell Crowe . Tugger follows Crowe as he engages various people in physical conflicts, providing emotional support and comic relief. At one point Tugger even attempts to commit suicide, upon being forced to hear Russell Crowe's new musical composition. (Alphabetical by author) Bollard pull Bollard pull
310-1178: Is equal to total resistance times velocity of the ship. P E = R T × V {\displaystyle P_{E}=R_{T}\times V} Total resistance is the sum of frictional resistance, R F {\displaystyle R_{F}} , residual resistance, R R {\displaystyle R_{R}} , and air resistance, R A {\displaystyle R_{A}} . R F = 1 2 × C F × ρ w × V w 2 × A s {\displaystyle R_{F}={\frac {1}{2}}\times C_{F}\times \rho _{w}\times V_{w}^{2}\times A_{s}} R R = 1 2 × C R × ρ w × V w 2 × A s {\displaystyle R_{R}={\frac {1}{2}}\times C_{R}\times \rho _{w}\times V_{w}^{2}\times A_{s}} R A = 1 2 × C A × ρ
341-403: Is known as drawbar pull , or tractive force , which is used to measure the total horizontal force generated by a locomotive , a piece of heavy machinery such as a tractor , or a truck , (specifically a ballast tractor ), which is utilized to move a load. Bollard pull is primarily (but not only) used for measuring the strength of tugboats , with the largest commercial harbour tugboats in
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#1732844426651372-412: Is not a typical tug, rather it is a special class of ship used in the petroleum industry called an Anchor Handling Tug Supply vessel . For vessels that hold station by thrusting under power against a fixed object, such as crew transfer ships used in offshore wind turbine maintenance, an equivalent measure " bollard push " may be given. Unlike in ground vehicles, the statement of installed horsepower
403-399: Is not sufficient to understand how strong a tug is – this is because the tug operates mainly in very low or zero speeds, thus may not be delivering power (power = force × velocity; so, for zero speeds, the power is also zero), yet still absorbing torque and delivering thrust. Bollard pull values are stated in tonnes -force (written as t or tonne) or kilonewtons (kN). Effective towing power
434-615: Is the carousel tug , winner of the Maritime Innovation Award at the Dutch Maritime Innovation Awards Gala in 2006. It adds a pair of interlocking rings to the body of the tug, the inner on the boat, the outer on the ship by winch or towing hook. Since the towing point rotates freely, the tug is very difficult to capsize. Vintage tugboat races have been held annually in Olympia, Washington , since 1974 during
465-406: Is the partial short circuit in propeller discharge current, the uneven trim of the ship and the short length of the tow line. All of these factors contribute to measurement error. This method eliminates much of the uncertainties of the practical trial. However, any numerical simulation also has an error margin. Furthermore, simulation tools and computer systems capable of determining bollard pull for
496-511: The Z-drive or ( azimuth thruster ) was developed. Although sometimes referred to as the Aquamaster or Schottel system, many brands exist: Steerprop , Wärtsilä , Berg Propulsion , etc. These propulsion systems are used on tugboats designed for tasks such as ship docking and marine construction. Conventional propeller/rudder configurations are more efficient for port-to-port towing. The Kort nozzle
527-409: The 2000-2010s having around 60 to 65 short tons-force (530–580 kN; 54–59 tf) of bollard pull, which is described as 15 short tons-force (130 kN; 14 tf) above "normal" tugboats. The worlds strongest tug since its delivery in 2020 is Island Victory (Vard Brevik 831) of Island Offshore , with a bollard pull of 477 tonnes-force (526 short tons-force; 4,680 kN). Island Victory
558-546: The 2000s–2010s, used for towing container ships or similar, had around 60 to 65 short tons-force (530–580 kN) of bollard pull, which is described as 15 short tons-force (130 kN) above "normal" tugboats. Tugboats are highly manoeuvrable, and various propulsion systems have been developed to increase manoeuvrability and increase safety. The earliest tugs were fitted with paddle wheels , but these were soon replaced by propeller-driven tugs. Kort nozzles (see below) have been added to increase thrust-to-power ratio. This
589-702: The New York State Canal System. Tugboat Annie was the subject of a series of Saturday Evening Post magazine stories featuring the female captain of the tugboat Narcissus in Puget Sound , later featured in the films Tugboat Annie (1933), Tugboat Annie Sails Again (1940) and Captain Tugboat Annie (1945). The Canadian television series The Adventures of Tugboat Annie was filmed in 1957. To date, there have been four children's shows revolving around anthropomorphic tugboats. "Tugger"
620-871: The Olympia Harbor Days Maritime Festival Tugboat races are held annually on Elliott Bay in Seattle , on the Hudson River at the New York Tugboat Race , the Detroit River , and the Great Tugboat Race and Parade on the St. Mary's River . Since 1980, an annual tugboat ballet has been held in Hamburg harbour on the occasion of the festival commemorating the anniversary of the establishment of
651-401: The below requirements, practical bollard pull trials need to be conducted in a deep water seaport , ideally not at the mouth of a river, on a calm day with hardly any traffic. See Figure 2 for an illustration of error influences in a practical bollard pull trial. Note the difference in elevation of the ends of the line (the port bollard is higher than the ship's towing hook). Furthermore, there
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#1732844426651682-425: The collective pitch control and cyclic in a helicopter. Tugboat fenders are made of high-abrasion-resistance rubber with good resilience properties. They are very popular with small port craft owners and tug owners. These fenders are generally made from cut pieces of vehicle tires strung together. Often the fendering on the sides of the tug is composed of large heavy equipment or aircraft tires attached to or hung on
713-420: The hull of a ship, which may have a pronounced rake at the bow and stern. In some ports there is a requirement for certain numbers and sizes of tugboats for port operations with gas tankers . Also, in many ports, tankers are required to have tug escorts when transiting in harbors to render assistance in the event of mechanical failure. The port generally mandates a minimum horsepower or bollard pull, determined by
744-430: The same as those used in railroad locomotives , but typically drive the propeller mechanically instead of converting the engine output to power electric motors, as is common for diesel-electric locomotives. For safety, tugboat engines often feature two of each critical part for redundancy. A tugboat is typically rated by its engine's power output and its overall bollard pull . The largest commercial harbour tugboats in
775-501: The side of the tug. Some fendering is compression moulded in high-pressure thermic-fluid-heated moulds and have excellent seawater resistance, but are not widely used owing to the cost. Tugboat bow fenders are also called beards or bow puds. In the past they were made of rope for padding to protect the bow, but rope rendering is almost never seen in recent times. Other types of tugboat fender include Tug cylindrical fender, W fender, M fender, D fender, and others. A recent Dutch innovation
806-742: The size of the escorted vessel. Most ports will have a number of tugs that are used for other purposes than ship assist, such as dredging operations, bunkering ships, transferring liquid products between berths, and cargo ops. These tugs may also be used for ship assist as needed. Modern ship assist tugs are "omni directional tugs" that employ propellers that can rotate 360 degrees without a rudder, like azimuthal stern drives (ASD), azimuthal tractor drives (ATD), Rotor tugs (RT) or cycloidal drives (VSP)(as described below). River tugs are also referred to as towboats or pushboats. Their hull designs would make open ocean operations dangerous. River tugs usually do not have any significant hawser or winch. Their hulls feature
837-473: The tug was seen being torn up for scrap on the Galcon Marine premises. Tugboat Seagoing tugs (deep-sea tugs or ocean tugboats) fall into four basic categories: Compared with seagoing tugboats, harbour tugboats that are employed exclusively as ship assist vessels are generally smaller and their width-to-length ratio is often higher, due to the need for the tugs' wheelhouse to avoid contact with
868-755: The tugs William Rest , the Lac Como , the G.W. Rogers and the Bagotville tried to free the lake freighter George M. Carl . The Toronto Harbour Commission occasionally employs the William Rest to break ice on the lower Don River . Port authorities retired the William Rest when they commissioned its replacement, the Iron Guppy , in the summer of 2016. William Rest was acquired by Galcon Marine Limited, but it has not been in active use since 2016. In November 2022,
899-400: The underside of the hull, rotating around a vertical axis with a circular array of vertical blades (in the shape of hydrofoils ) that protrude out of the bottom of the ship. Each blade can rotate itself around a vertical axis. The internal mechanism changes the angle of attack of the blades in sync with the rotation of the plate, so that each blade can provide thrust in any direction, similar to
930-470: The world towing and ship berthing. Tugboat diesel engines typically produce 500 to 2,500 kW ( ~ 680 to 3,400 hp ), but larger boats (used in deep waters) can have power ratings up to 20,000 kW (~ 27,200 hp) . Tugboats usually have an extreme power : tonnage -ratio; normal cargo and passenger ships have a P:T-ratio (in kW: GRT ) of 0.35 to 1.20, whereas large tugs typically are 2.20 to 4.50 and small harbour-tugs 4.0 to 9.5. The engines are often
961-474: Was followed by the nozzle-rudder, which omitted the need for a conventional rudder . The cycloidal propeller (see below) was developed prior to World War II and was occasionally used in tugs because of its maneuverability. After World War II it was also linked to safety due to the development of the Voith Water Tractor, a tugboat configuration that could not be pulled over by its tow. In the late 1950s,