Tugboats : The 'Worker Bee' of the Harbour

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Harbours come loaded with all types of boats...from large cargo vessels, oil tankers to something glamorous like the cruise-liners and to simple 'transporters' like hovercrafts and ferries. Of course we have our yachts doing all the servicing of the luxurious kind...

...but how does one take the bigger, bulkier vessels safely and securely into their berths...since these need utmost care while being 'parked'...but having an obvious disadvantage due to their size and other mechanical limitations, they are tough to manouver into their spots.


For such uses, there are special-purpose boats known as tugboats or tugs that like Worker Bees...have the responsibility of servicing the bigger Queens of the Harbour...

TUGBOATS

A tugboat, or tug, is a boat used to maneuver, primarily by towing or pushing, other vessels in harbours, over the open sea or through rivers and canals. Tugboats are also used to tow barges, disabled ships, or other equipment like towboats.


Tugboats are quite strong for their size. Early tugboats had steam engines; today diesel engines are used. Tugboat engines typically produce 750 to 3,000 horsepower, but larger boats (used in deep waters) can have power ratings up to 25,000 hp and usually have an extreme power:tonnage-ratio.

MANOUVERABILITY

Tugboats are highly maneuverable, and various propulsion systems have been developed to increase maneuverability and increase safety.

The earliest tugs were fitted with paddle wheels, but these were soon replaced by propeller-driven tugs.

Kort nozzles have been added to increase thrust per hp. This was followed by the nozzle-rudder, which omitted the need for a conventional rudder. The 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.

A tugboat's power is typically stated by its engine's horsepower and its overall Bollard pull.

KORT NOZZLE

The Kort nozzle 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.

TYPES OF TUGBOATS

There are two groups of tugboats, either 1) Inland or 2) Oceangoing.

1) Inland tugboats come in two categories :-

i) Harbor or Harbour tugs are the most typical of the tugboats that people recognize. They are used worldwide to move ships in and out of berth and to move industrial barges around waterfront business complexes.

ii) River tugs are also referred to as towboats or pushboats. They are designed as large squared-off vessels with flat bows for connecting with the rectangular stern of the barges.

2) Oceangoing tugboats come in four categories :-

i) The conventional tug.

ii) The notch tug.

iii) The articulated tug and barge, or ATB.

iv) The integrated tug and barge, or ITB, (which is a rigidly connected tug and barge).

Next time you get into the harbor and see a tugboat give it the respect it deserves...