Tugboats are a special vessel used mainly near the harbor and ports to assist in docking of the ships. As discussed in my older post “Types of Boats“; a tug boat is a powerful vessel in small form that use push or pull to do its job. Its primary job is to assist large ships during maneuvering and docking operation.
The other use of a tugboats is to tug or pull barges; oil platform, disabled ships to carry them to secured position. Not just that, many a times they are also used as ice breakers do fire fighting duties and act as a salvage boat. It is also not uncommon to see them performing escort for large ship in narrow waters.
With average power of 700 to 3500hp they are quite powerful in deep and shallow waters. Being one of the first vessels to incorporate steam propulsion; they are considered pioneer in the development of shipping industry. These small yet powerful watercraft was first build in 1736; for the support and salvage operation in Clyde Canal ( Scotland ).
The two main advantages of tugboats over other watercraft’s and ships is; its ability to maneuver easily in the most restrictive waters and its high power to weight ratio. Tugboats are not just more powerful for their size but equally more strong and solid. They can be seen in rivers, near ports and out in ocean; yet only a few notice their presence due to its small size.
What Are Tugboats Used For & Why They Used For That Purpose?
Ships began to grow bigger and bigger with the development of the shipping industry starting from late 20th century. In less than a century they become so large; it practically become impossible to turn the ship in narrow channels or near ports. Since each sip is required to dock in a preassigned position; tugboats become an important aspects of shipping industry.
Over all these time they have been used to tow, assist and escort ships near ports and in congested waters. Thanks to its solid structure and high power to weight ratio; they also act as salvage boat, icebreakers and utility boats for barges and oil platforms. Many a times they are also seen as shifting offshore drilling platforms.
Based on these specific use and area of operation; a tugboat can be classified into 3 main types:
1 ) Seagoing Tugboats
Made with high strength material these boats are built to go out in international waters and generally have the most powerful engines. A little bigger than its other sub types; they have a power to tonnage ratio of about 2:4.5 to 2.2:5. Equipped with towing lines they tow ships, other boats and other watercraft’s.
Out in the open sea they salvage ships and boats that undergo engine failure; or receive significant damage from collision or grounding. These vessels are then towed using a towing lines capable of handling ships of much larger sizes with free movement. This free movement of towing lines are often ensured by having a low aft deck structure.
Ranging from 150 to 250 feet in length these boats are generally called upon to do heavy duty jobs at sea; such as shifting drilling platform, barges, and damaged ships. Other than that they are also used for fire fighting and other emergency responses at sea. Other than that ther are often used in navy across the world for support and patrol purposes.
2 ) Harbor Tugboats
A harbor tug is the one we usually see near ports handling and supporting proper docking of the ships. These tugboats do this by using push and pull to rotate and position ship in particular position. Its hard for any ship to turn 360 degree in such congested water; and if it wasn’t be these tugs it would be a challenge.
They are designed for both assisting and towing purposes and so are generally termed as multi purpose tugboats. Having such high demands they have higher power to tonnage ratio; in comparison with other tugboats of 4:10 or 3.9:9.5. The majority of harbor tug that we see are of azimuth stern drive type.
In some case you may also find another more powerful tugboat called tractor tug; which includes benefits such as 360 degree turning at full capacity while towing a ship. The other benefits include instant power, better control, excellent maneuverability and better response. Irrespective of its type ( azimuth stern drive vs tractor tug ) harbor tugs have the most maneuverability than others.
3 ) Escort Tugboats
If you ever been on any ship without bow thruster you must have noticed tugs assisting in your ship near canals and in area with narrow passage. These specialized tugboats which are designed to assist in maneuverability of very large ships; in restricted waters are best known as the escort tugboats.
Other than that escort tugs came into rescue; when your ships main propulsion system fails or have trouble steering the ship. Thus you can find them near canals, harbors, ports and channels; where there is huge risks of pollution and maritime safety due to engine failure or steering gear defects.
Thus the first escort tugboat was used for an oil tanker in 1975. On many ports around the world having an escort tugboat is made compulsory as part of safety. The boat can use both direct or indirect mode of operation or either of the two. Thanks to growing size of ships newer tugs are having more and more bollard pull.
How Tugboats Work Or Do Its Job
Although tugboats look much small and helpless with respect to big ship but it drastically reduce the berthing time. Even with ships using bow thruster; a tug can rotate them 10 times faster than using big bow thruster. That is achieved by the sound grip of the tugs on ships hull, its powerful engines and simple forces such as push or pull.
A tug do its job by using either the direct approach or indirect ones. Most conventional and azimuth harbor tugs often works in team and push the ship in order to turn it. They use their high power engine ( 3 to 4 thousand hp ) and heavy displacement hull to generate more grip and displacement in water.
They use a turbocharged four stroke marine diesel engine with computer monitored fuel injection system; that provide enough power to tow most ships by their own. Having low freeboard with heavy displacement hull design make sure the tug stay low in water. This helps generate more friction with water meaning more power with a steady boat.
In the indirect approach tractor tugs and azimuth harbor tugs hook on to the back of the ship; now using the towing line and its powerful propulsion it turn the ship on its own. With that being said i do not want to neglect the importance of waves, wind and weather condition that affects this process.
How Powerful Is A Tugboat And How Come It Able To Toe Large Ships?
The power and capability of a tug boat is measured in the form of its maneuverability and engine power. The power is determined by the amount of torque the engine produces or horse power. Similarly the ability turn, pickup speed and stop within record time and distance determine its maneuverability.
On average a tug can have engine with power in between 3 to 6 thousand horse power. An 3 thousand horse power engine can allow tugs to toe ships as large as an aircraft carrier. It is for the ULCC that tugs of greater power are required. Similarly a tug should be capable of turning complete 360 degree almost within her length.
Moreover it must go from its maximum speed forward to maximum speed back in not less than 15 seconds. The reason for all this power and agility is simple; to be able to toe large ships maintaing safe maritime passage. Thanks to the unique ability of water to exert less friction; any small vessel can push or pull a large ship.
These tugs are equipped with strengthen winch and additional stability that helps them exert more torque and strain on the towing line; thus exerting force to toe the ship. To turn they also apply forward push in teams of two and three on dedicated positions on the ships hull. All big ships have these soft positions marked on hull; making it easier for tugs to do their job.
Common Doubts & Questions ( Tugboats )
Q.1. Why do some tug boats spray water near ports?
Ans: While its not much of a required job or event but rather a long ceremonial custom to welcome arriving ship at port. Right from the early days of shipping its in tradition to spray water in air using fire hydrants and nozzles. This is done to give due respect to any vessel or on special occasions.
Q.2. Why Does Tugs Stays Far Ahead Of The barges Or Ship It Toe?
Ans: There is no such thing as brakes in water and you will not stop just because your engines are on hold or down. In condition when a ship or barge ( a water vessel without engine ) is toed by a tug; it is common practice to maintain a safe distance. If not there can be accidents and the barge or ship can collide with the tug.
Q.3. Does Tugs Too Have Anchors?
Ans: Every water board vessel that have its own propulsion system have an anchor. It is another thing that its not that big as many other boats of similar size or power do have. It is so because they are mostly in service and rarely required to anchor and wait for the orders. They can have either conventional anchor or the one which they can lower with the windlass.
Q.4. Why Do Most Tugs Push More Than Pull?
Ans: Since a majority of tugs are used near harbor and ports they generally assist in berthing/docking of the large ships. On most occasions they are not required to toe; and so it always easier and safe to push the ship on marked position to turn it using tugs. That is the reason why many people find them pushing near ports; but away from ports they usually toe or pull other water vessels. Even in ports bigger tugs tends to pull more than pushing them.
- What Are Container Ship ? – Its Type, Dimension And Function
- Best Handheld VHF Marine Radio | Review & Comparison
- Life At Sea | Experience Of New Joiners On Merchant Ship
- What Are The Different Boat Types? | Explained With Pictures
- What Is The Best Way To Avoid Overloading Your Boat?