10 Ship Terms And Definitions: Commonly Misunderstood Nautical Terms

Ship Terms and Definitions: Although a lot of these ship terms are common, even the smartest people don’t fully understand the true meaning of some of them.

Nautical terms might sound foreign to beginners, but they’re rooted in tradition. They’re practical and will boost your confidence once you’ve mastered them. Here’s how to talk like a sailor – but remember that a boat is more than words.

Here are some of the most misunderstood and misused ship terms.

10 Commonly Misunderstood Ship Terms And Definitions

1. Watertight and weatherproof doors

While these ship terminology may not be especially well-known to those outside the business, maritime professionals are familiar with them.

The positioning of these two ship entrances is the primary distinction between them.

The majority of weathertight doors are found above the vessel’s waterline. Their purpose is to stop water from entering from the outside. Usually, this includes a little water head. Their primary function is to stop green seas from entering the area of the ship that they are intended to defend. On tanker tankers, weathertight doors are found on the majority of deck and accommodation doors. Because these doors open outward, a water draught won’t affect them because there will be a positive pressure.

Conversely, watertight doors safeguard the watertight integrity of the adjacent compartment of the ship by preventing water infiltration from both directions. Watertight doors are made to open and close any way, usually automatically, and are situated below deck level. On vehicle carrier vessels and Ro-Ro decks, the majority of doors are waterproof. Regulations demand that watertight door statuses (open/close) be indicated remotely.

2. The Net and Gross Tonnage

Even though they are well known in daily life, some ship terminology and meanings are frequently misapplied on board.

The total volume of a ship’s enclosed spaces is known as its gross tonnage. This also applies to other non-cargo areas like the engine room. The complicated formula used to compute the tonnage is outside the purview of this article. Ships are subject to the majority of maritime regulations (SOLAS, MARPOL, etc.) according to their gross tonnage.

Conversely, net tonnage is the volume of the ship’s cargo carrying capacity alone. The vessel’s tonnage determines its earning potential. Ships are often subject to port/anchorage dues based on their net tonnage.

  • Suez Canal Tonnage, which computes the toll for traversing the canal using a slightly different method, should not be confused with Gross and Net Tonnage.
  • Gross Registered Tonnage (GRT) and Net Registered Tonnage (NRT) are not to be confused with Gross Tonnage (GT) and Net Tonnage (NT). The occasional elderly seafarer will still refer to tons as GRT and NRT. Prior to the 1969 International Convention on Tonnage Measurement of Ships (IMO Convention), GRT and NRT were in use. These terms are now out of use. In 1994, GT and NT took their place by tradition.

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3. Bay and Gulf

Bay and Gulf differences

There are many different types of water bodies in the world, including rivers, lakes, straits, canals, bays, oceans, and seas. Most of these are obvious. The majority of individuals, however, are unable to distinguish between a bay, a strait, a channel, and a canal.

Gulf: A gulf is, by definition, a wide body of water having a narrow entrance along a strait, sometimes regarded as an extended arm of a sea. Land encloses a gulf nearly completely.

For instance, the Gulf of Mexico, the Gulf of Finland, and the Persian Gulf

Bay: A bay is comparable to a gulf, however, it is often larger at the entrance and smaller in size. There are certain exclusions from this definition, though. For example, the Bay of Bengal is substantially bigger than the majority of bays worldwide. Additionally, land does not completely encircle a bay.

such as the Bay of Bengal and the Bay of Biscay.

Bengal Bay Bays Picture courtesy of www.wikipedia.com

4. Canals, Straits, and Channels

Suez Canal History, Suez Canal, Suez Canal importance
(Credit: Britannica)

A strait is a narrow body of water that connects two significantly bigger bodies of water, like Singapore and Malacca. The South China Sea and the Bay of Bengal are connected by straits. There is tidal movement of water in both directions. Most significantly, straits emerge naturally without the help of humans.

For instance, the Straits of Gibraltar, the Straits of Hormuz, the Straits of Sunda, the Straits of Singapore, and the Straits of Lombok.

Wider Straits are referred to as strait channels. They are larger and have more navigable water, but otherwise they are similar to the Straits.

For instance, Mozambique Channel, English Channel

Canals are human-made straits. It is a man-made canal designed to shorten the distance between natural pathways and enable trade along otherwise hazardous routes.

For instance, the Panama, Kiel, and Suez canals.

5. Specific Gravity and Density

These ship phrases are primarily related to the crew and tanker officers.

By definition, density is the mass of matter per unit volume. Alternatively put, bulk above volume. As a result, kg/cm3 values are used.

For instance, seawater has a density of about 1025 kg/m3.

The specific gravity of a substance is calculated by dividing its density by a reference material, usually fresh water. Often called a ration, the units balance each other out.

For instance, diesel oil has a specific gravity of 0.86.

Since fresh water has a density of 1.0 kg/cm3, its specific gravity and density are the same when used as a reference.

6. Dolphins, bilge, chocks, bitts, and bollards

Chocks on Ships, Chocks, Chocks design
(Credit: YSmarines)

Terms like “fairleads,” “chocks,” “bitts,” “bollards,” “dolphins,” etc. are frequently used when anchoring a vessel.

Fairleads: are fused directly to the hull structure of the ship. A roller is fastened to fairleads to direct mooring wires to winches for the appropriate lead. Modern ships typically have pedestal fairleads to guide mooring lines between the winch and the chock. Previously, Universal Fairleads frequently used ships in place of chocks.

Chocks: Ships with chocks are structural reinforcements that direct mooring lines to and from other vessels and the land. When a vessel is moored, chocks must be substantially stronger than the mooring line in order to prevent structural damage and endure different forces.

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Bollards: Generally speaking, these are little stakes that are used to secure ship mooring lines on the dock or pier. On a ship, a single bitt is also known as a bollard, on which the rope’s eye is fastened. Cruciform bollards are unique bollards found in several locations on oil tankers that are designed to support and secure flexible hoses utilized for cargo operations.

Bitts are twin bollards or posts that are vertically positioned on ships and used to tug lines, secure fire wires on tankers, and secure mooring lines from other boats (during STS operations). Bitts can never be found alone. To make sure that the tug does not pull the vessel with more force than necessary, it is crucial to let the pilot or tug operator know the SWL of the bitts.

Dolphins: They can only be found on land. These are separate jetty platforms that include bollards or hooks to fasten the ship’s mooring lines.

Bilge: The lowest compartment of a ship or boat is called the bilge.

7. Cranes And Derricks

Crane Barge Specialized Floating Lifting Device, what is Crane Barge, purpose of Crane Barge
(Credit: KTU Shipyard)

Cranes and derricks are two ship terminology for hoisting apparatus. Derricks are only seen on a few antique ships and are now a thing of the past. The considerably simpler and more adaptable Deck Crane has taken their place.

Derrick: A derrick is a hoisting apparatus that consists of one or more guy masts, or structural elements. Several lines attached to the mast’s top control the lateral and vertical motion of a derrick. A separate line that functions as a crane does the runner-up/down function to raise and lower a load.

The Union Purchase Rig, which employs two derricks to load and unload cargo far more quickly than single derricks, is the most widely used derrick on ships.

The Derrick’s inability to quickly adapt the rig to varied lifts and types of cargo is one of its main drawbacks. Additionally, at least two winch operators are needed to operate derricks.

Cranes: Derricks and cranes are comparable, but crane operation is far simpler. A single crane driver performs all operations, including runner up/down, boom up/down, side swinging, etc. The majority of shipboard cranes are made to swing 360 degrees, but some additionally come equipped with safety limit valves that stop them from working at angles that could harm nearby structures. To stop the runner wire from reaching the drum’s end, limit switches are also included.

8. Swinging Circle And Turning Circle

Turning circles and swinging circles are two ship navigational phrases that are sometimes misconstrued.

The term “swinging circle” in shipping refers to a vessel that is at anchor. This is the approximate radius that the ship should swing when at anchor. The formula for calculating the radius of a swinging circle is typically (Number of Shackles x 27.5 m + Ship Length in Meters). Following anchoring, the watch officer (OOW) is responsible for making sure the vessel stays inside its swinging circle and that no other vessel anchors there as well as maintaining a safety distance that the master determines. The amount of shackles that are handed out determines the swinging circle, which is not fixed.

One of the vessel’s maneuvering features is the Turning Circle. It is the circumference of the vessel when the rudder is fully extended when moving forward at full speed. Usually, during the sea testing of the vessel before to delivery, this shipping term is decided. For both shallow and deep waters, the yard will provide specifics about the turning circles in loaded and ballast conditions. The Wheelhouse Poster and the bridge both have turning circles posted, so there’s no need to compute the turn procedure every time or under every set of circumstances.

9. The Gangway and the Accommodation Ladders

These two terms are still most frequently used interchangeably on ships. Nevertheless, they have the same goal. For example, their rigging and use are distinct, and they act as a link or bridge between the ship and the shore.

Gangways: The ship’s fore and aft lines are lined up at a right angle to the gangways. Gangways must not be used at an angle steeper than thirty degrees to the horizontal. Any vessel longer than thirty meters must have gangways. Only railings reinforced for this reason may be used to rig gangways.

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Accommodation Ladders face astern and are rigged in the ship’s fore and aft directions. The greatest inclination angle from the horizontal can’t be more than 55 degrees. Typically, accommodation ladders are fastened to the vessel and swung out with the aid of specialized winches and motors. These are required for any vessel longer than 120 meters.

10. Protocol, Code, Convention, and Annex

Of all the ship words and definitions, the one above stands out as the most ambiguous. Let’s examine the values that each represents.

The convention is a legal commitment between signing governments to abide by the terms of the agreement, which serves as the foundation for the treaty. Member countries cannot ratify conventions unless the IMO has adopted them.

Such as the Maritime Labour Convention, the SOLAS Convention, the MARPOL Convention, the Loadline Convention, etc.

In the merchant shipping sector, a convention is only binding on all member states once it has received official IMO approval and member state ratification. This article does not address the rules of convention adoption (tacit and active acceptance).

A protocol is an additional agreement that amends a convention. It is a treaty that enhances or adds to an earlier agreement. It is simpler to improve the convention with a protocol than to introduce a whole new one.

For instance, MARPOL 73/78 refers to the 1978 Protocol’s update to the 1973-formalized International Convention for the Prevention of Pollution from Ships. Due to a deficiency of ratifications, the merged convention was not put into effect until 1983.

  • Code: A code is a section of a convention that includes numerous technical specifications for the convention’s key components. Put differently, a code helps to elaborate on the convention’s contents. It is an integral aspect of a convention and cannot be a stand-alone rule.

For example, the SOLAS convention includes the ISPS Code (International Ship and Port Facility Security Code), and the LSA and FSS Codes are also included in the same conventions.

  • Annexe: An Annex is a component of a convention that is added after it has been formally established. For an annex to an IMO convention to be legally obligatory on all member states, each member state must independently ratify the annex.

For example, since the convention’s first implementation, member nations have accepted each of the six annexes that currently make up MARPOL at different times.

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