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Ship dimensions, form, size, or category
2 Ship dimensions, form, size, or category Chapter Outline Oil tankers 13 Bulk carriers 13 Container ships 15 IMO oil tanker categories 15 Panama canal limits 15 Suez canal limits 16 Some useful websites 16
The hull form of a ship may be defined by a number of dimensions and terms that are often referred to during and after building the vessel. An explanation of the principal terms is given below: After Perpendicular (AP): A perpendicular drawn to the waterline at the point where the after side of the rudder post meets the summer load line. Where no rudder post is fitted it is taken as the center line of the rudder stock. Forward Perpendicular (FP): A perpendicular drawn to the waterline at the point where the fore-side of the stem meets the summer load line. Length Between Perpendiculars (LBP): The length between the forward and aft perpendiculars measured along the summer load line. Amidships: A point midway between the after and forward perpendiculars. Length Overall (LOA): Length of vessel taken over all extremities. Lloyd’s Length: Used for obtaining scantlings if the vessel is classed with Lloyd’s Register. It is the same as length between perpendiculars except that it must not be less than 96% and need not be more than 97% of the extreme length on the summer load line. If the ship has an unusual stem or stern arrangement the length is given special consideration. Register Length: The length of ship measured from the fore-side of the head of the stem to the aft side of the head of the stern post or, in the case of a ship not having a stern post, to the fore-side of the rudder stock. If the ship does not have a stern post or a rudder stock, the after terminal is taken to the aftermost part of the transom or stern of the ship. This length is the official length in the register of ships maintained by the flag state and appears on official documents relating to ownership and other matters concerning the business of the ship. Another important length measurement is what might be referred to as the IMO Length. This length is found in various international conventions such as the Load Line, Tonnage, SOLAS and MARPOL conventions, and determines the application of requirements of those conventions to a ship. It is defined as 96% of the total length on a waterline at 85% of Ship Construction. DOI: 10.1016/B978-0-08-097239-8.00002-7 Copyright Ó 2012 Elsevier Ltd. All rights reserved.
12
Ship Construction
the least molded depth measured from the top of keel, or the length from the fore-side of stem to the axis of rudder stock on that waterline, if that is greater. In ships designed with a rake of keel the waterline on which this length is measured is taken parallel to the design waterline.
Molded dimensions are often referred to; these are taken to the inside of plating on a metal ship. Base Line: A horizontal line drawn at the top of the keel plate. All vertical molded dimensions are measured relative to this line. Molded Beam: Measured at the midship section, this is the maximum molded breadth of the ship. Molded Draft: Measured from the base line to the summer load line at the midship section. Molded Depth: Measured from the base line to the heel of the upper deck beam at the ship’s side amidships. Extreme Beam: The maximum beam taken over all extremities. Extreme Draft: Taken from the lowest point of keel to the summer load line. Draft marks represent extreme drafts. Extreme Depth: Depth of vessel at ship’s side from upper deck to lowest point of keel. Half Breadth: Since a ship’s hull is symmetrical about the longitudinal centre line, often only the half beam or half breadth at any section is given. Freeboard: The vertical distance measured at the ship’s side between the summer load line (or service draft) and the freeboard deck. The freeboard deck is normally the uppermost complete deck exposed to weather and sea that has permanent means of closing all openings, and below which all openings in the ship’s side have watertight closings. Sheer: A rise in the height of the deck (curvature or in a straight line) in the longitudinal direction. Measured as the height of deck at side at any point above the height of deck at side amidships. Camber (or Round of Beam): Curvature of decks in the transverse direction. Measured as the height of deck at center above the height of deck at side. Straight line camber is used on many large ships to simplify construction. Rise of Floor (or Deadrise): The rise of the bottom shell plating line above the base line. This rise is measured at the line of molded beam. Large cargo ships often have no rise of floor. Half Siding of Keel: The horizontal flat portion of the bottom shell measured to port or starboard of the ship’s longitudinal center line. This is a useful dimension to know when drydocking. Tumblehome: The inward curvature of the side shell above the summer load line. This is unusual on modern ships. Flare: The outward curvature of the side shell above the waterline. It promotes dryness and is therefore associated with the fore end of ship. Stem Rake: Inclination of the stem line from the vertical. Keel Rake: Inclination of the keel line from the horizontal. Trawlers and tugs often have keels raked aft to give greater depth aft where the propeller diameter is proportionately larger in this type of vessel. Small craft occasionally have forward rake of keel to bring propellers above the line of keel. Tween Deck Height: Vertical distance between adjacent decks measured from the tops of deck beams at ship’s side. Parallel Middle Body: The length over which the midship section remains constant in area and shape.
Ship dimensions, form, size, or category
13
Entrance: The immersed body of the vessel forward of the parallel middle body. Run: The immersed body of the vessel aft of the parallel middle body. Tonnage: This is often referred to when the size of the vessel is discussed, and the gross tonnage is quoted from Lloyd’s Register. Tonnage is a measure of the enclosed internal volume of the vessel (originally computed as 100 cubic feet per ton). This is dealt with in detail in Chapter 30. Deadweight: This is defined in Chapter 1. It should be noted that for tankers deadweight is often quoted in ‘long tons’ rather than ‘metric tons (tonnes)’; however, MARPOL regulations for oil tankers are in metric tons.
The principal dimensions of the ship are illustrated in Figure 2.1. TEU and FEU: Indicate the cargo-carrying capacity of container ships. TEU (twenty-foot equivalent unit) indicates the number of standard shipping containers that may be carried on some shipping routes; container ships may carry standard containers that are 40 feet in length. FEU is forty-foot equivalent unit.
An indication of the size by capacity of oil tankers, bulk carriers, and container ships is often given by the following types:
Oil tankers l
l
l
l
l
l
ULCC (Ultra-Large Crude Carrier) is a tanker usually between 300,000 and 550,000 tonnes deadweight. VLCC (Very Large Crude Carrier) is a tanker usually between 200,000 tonnes and 300,000 tonnes deadweight. Suezmax indicates the largest oil tanker that can transit the current Suez Canal fully laden, being about 150,000 tonnes deadweight. Aframax the standard designation of smaller crude oil tankers, being the largest tanker size in the AFRA Freight Rate Assessment Scale Large One Category. AFRA stands for ‘American Freight Rate Association’. Variously reported as being 80,000 to 115,000 tones deadweight. Panamax is the maximum size of oil tanker, with beam restriction of 32.2 meters and length restriction of 275 meters, that can transit the Panama Canal prior to completion of the planned new locks. Typical size is about 55,000–70,000 tonnes deadweight. Handysize/Handymax are typical product tankers of about 35,000–45,000 tonnes deadweight.
Bulk carriers l
l
l
l
Capesize ships that are too large to transit the current Panama Canal and therefore voyage around Cape Horn. All bulk carriers above 80,000 tonnes deadweight fall into this category. Most are up to 170,000 tonnes deadweight but a small number are larger for specific trade routes, the biggest being 365,000 tonnes deadweight. Panamax—As for oil tankers. Handymax ships are between around 35,000 and 60,000 tonnes deadweight. Ships between 10,000 and 35,000 tonnes deadweight have formed the majority of the fleet for many years and are designated ‘Handysize’. In recent years the size of these ships has been increasing and the term ‘Handymax’ has been applied to designate the larger bulk carriers.
14
Sheer forward
Sheer aft
Freeboard Summer load line Amidships
Length between perpendiculars (LBP) Length on waterline (LWL) Length overall (LOA) Aft perpendicular
Ford perpendicular Tumblehome
Camber
Depth Molded beam
Draft
Base line
Rise of floor Half siding of keel
Ship Construction
Figure 2.1 Principal ship dimensions.
Ship dimensions, form, size, or category
15
Container ships l
l
l
l
l
Ultra-large container ships. Ships with a capacity of over 14,000 TEU. Few have been built to date. These ships are too large for any canals. Post-Panamax ships are too large to transit the current Panama Canal and undertake transocean voyages. Their size is typically 5500–8000 TEU though larger ships with over 10,000 TEU capacity have been built. New Panamax ships (including most Post-Panamax ships) would be able to transit the expanded Panama Canal. They may carry up to around 12,000 TEU. Panamax ships that can transit the current Panama Canal carry between 3000 and 5000 TEU. Feeder ships are smaller vessels that do not undertake oceanic voyages but are generally engaged in shipping containers. The smallest of these may only carry several hundred TEU. There is no specific subclass below Panamax size.
IMO oil tanker categories l
l
l
Category 1 (commonly known as Pre-MARPOL tankers) includes oil tankers of 20,000 tonnes deadweight and above carrying crude oil, fuel oil, heavy diesel oil, or lubricating oil as cargo, and of 30,000 tonnes deadweight and above carrying other oils, which do not comply with the requirements for protectively located segregated ballast tanks. These ships have been phased out under IMO regulations. Category 2 (commonly known as MARPOL tankers) includes oil tankers of 20,000 tonnes deadweight and above carrying crude oil, fuel oil, or lubricating oil as cargo, and of 30,000 tonnes deadweight and above carrying other oils, which do comply with the protectively located segregated ballast tank requirements. These ships are due to be phased out. Category 3 includes oil tankers of 5000 tonnes deadweight and above but less than the tonnes deadweight specified for Categories 1 and 2. Also due to be phased out.
Note: For tankers carrying HGO (heavy gas oil) the lower limits for Categories 2 and 3 fall to 600 tonnes deadweight.
Panama canal limits These are set by lock sizes. Current locks are ‘Panamax’. New locks will be larger for ‘New Panamax’ ships (see Table 2.1). Table 2.1 Panama Canal limits
Length (m) Breadth (m) Draft (m)
Panamax ships
New Panamax ships
294.13 32.81 12.04
366 49 15.2
16
Ship Construction
Suez canal limits There are no locks and ship size is limited by the canal dimensions. There is a maximum breadth limit of 75 meters. With no locks the ship length is also unrestricted. The maximum draft is 20 meters. The Saint Lawrence Seaway links the North American Great Lakes to the Atlantic. The limits for ships based on the locks are length 226 m, breadth 24 m, and draft 7.92 m.
Some useful websites www.pancanal.com/eng/general For details of Panama Canal. http://www.suezcanal.gov.eg http://www.greatlakes-seaway.com
The hull form of a ship may be defined by a number of dimensions and terms that are often referred to during and after building the vessel. An explanation of the principal terms is given below: After Perpendicular (AP): A perpendicular drawn to the waterline at the point where the after side of the rudder post meets the summer load line. Where no rudder post is fitted it is taken as the center line of the rudder stock. Forward Perpendicular (FP): A perpendicular drawn to the waterline at the point where the fore-side of the stem meets the summer load line. Length Between Perpendiculars (LBP): The length between the forward and aft perpendiculars measured along the summer load line. Amidships: A point midway between the after and forward perpendiculars. Length Overall (LOA): Length of vessel taken over all extremities. Lloyd’s Length: Used for obtaining scantlings if the vessel is classed with Lloyd’s Register. It is the same as length between perpendiculars except that it must not be less than 96% and need not be more than 97% of the extreme length on the summer load line. If the ship has an unusual stem or stern arrangement the length is given special consideration. Register Length: The length of ship measured from the fore-side of the head of the stem to the aft side of the head of the stern post or, in the case of a ship not having a stern post, to the fore-side of the rudder stock. If the ship does not have a stern post or a rudder stock, the after terminal is taken to the aftermost part of the transom or stern of the ship. This length is the official length in the register of ships maintained by the flag state and appears on official documents relating to ownership and other matters concerning the business of the ship. Another important length measurement is what might be referred to as the IMO Length. This length is found in various international conventions such as the Load Line, Tonnage, SOLAS and MARPOL conventions, and determines the application of requirements of those conventions to a ship. It is defined as 96% of the total length on a waterline at 85% of Ship Construction. DOI: 10.1016/B978-0-08-097239-8.00002-7 Copyright Ó 2012 Elsevier Ltd. All rights reserved.
12
Ship Construction
the least molded depth measured from the top of keel, or the length from the fore-side of stem to the axis of rudder stock on that waterline, if that is greater. In ships designed with a rake of keel the waterline on which this length is measured is taken parallel to the design waterline.
Molded dimensions are often referred to; these are taken to the inside of plating on a metal ship. Base Line: A horizontal line drawn at the top of the keel plate. All vertical molded dimensions are measured relative to this line. Molded Beam: Measured at the midship section, this is the maximum molded breadth of the ship. Molded Draft: Measured from the base line to the summer load line at the midship section. Molded Depth: Measured from the base line to the heel of the upper deck beam at the ship’s side amidships. Extreme Beam: The maximum beam taken over all extremities. Extreme Draft: Taken from the lowest point of keel to the summer load line. Draft marks represent extreme drafts. Extreme Depth: Depth of vessel at ship’s side from upper deck to lowest point of keel. Half Breadth: Since a ship’s hull is symmetrical about the longitudinal centre line, often only the half beam or half breadth at any section is given. Freeboard: The vertical distance measured at the ship’s side between the summer load line (or service draft) and the freeboard deck. The freeboard deck is normally the uppermost complete deck exposed to weather and sea that has permanent means of closing all openings, and below which all openings in the ship’s side have watertight closings. Sheer: A rise in the height of the deck (curvature or in a straight line) in the longitudinal direction. Measured as the height of deck at side at any point above the height of deck at side amidships. Camber (or Round of Beam): Curvature of decks in the transverse direction. Measured as the height of deck at center above the height of deck at side. Straight line camber is used on many large ships to simplify construction. Rise of Floor (or Deadrise): The rise of the bottom shell plating line above the base line. This rise is measured at the line of molded beam. Large cargo ships often have no rise of floor. Half Siding of Keel: The horizontal flat portion of the bottom shell measured to port or starboard of the ship’s longitudinal center line. This is a useful dimension to know when drydocking. Tumblehome: The inward curvature of the side shell above the summer load line. This is unusual on modern ships. Flare: The outward curvature of the side shell above the waterline. It promotes dryness and is therefore associated with the fore end of ship. Stem Rake: Inclination of the stem line from the vertical. Keel Rake: Inclination of the keel line from the horizontal. Trawlers and tugs often have keels raked aft to give greater depth aft where the propeller diameter is proportionately larger in this type of vessel. Small craft occasionally have forward rake of keel to bring propellers above the line of keel. Tween Deck Height: Vertical distance between adjacent decks measured from the tops of deck beams at ship’s side. Parallel Middle Body: The length over which the midship section remains constant in area and shape.
Ship dimensions, form, size, or category
13
Entrance: The immersed body of the vessel forward of the parallel middle body. Run: The immersed body of the vessel aft of the parallel middle body. Tonnage: This is often referred to when the size of the vessel is discussed, and the gross tonnage is quoted from Lloyd’s Register. Tonnage is a measure of the enclosed internal volume of the vessel (originally computed as 100 cubic feet per ton). This is dealt with in detail in Chapter 30. Deadweight: This is defined in Chapter 1. It should be noted that for tankers deadweight is often quoted in ‘long tons’ rather than ‘metric tons (tonnes)’; however, MARPOL regulations for oil tankers are in metric tons.
The principal dimensions of the ship are illustrated in Figure 2.1. TEU and FEU: Indicate the cargo-carrying capacity of container ships. TEU (twenty-foot equivalent unit) indicates the number of standard shipping containers that may be carried on some shipping routes; container ships may carry standard containers that are 40 feet in length. FEU is forty-foot equivalent unit.
An indication of the size by capacity of oil tankers, bulk carriers, and container ships is often given by the following types:
Oil tankers l
l
l
l
l
l
ULCC (Ultra-Large Crude Carrier) is a tanker usually between 300,000 and 550,000 tonnes deadweight. VLCC (Very Large Crude Carrier) is a tanker usually between 200,000 tonnes and 300,000 tonnes deadweight. Suezmax indicates the largest oil tanker that can transit the current Suez Canal fully laden, being about 150,000 tonnes deadweight. Aframax the standard designation of smaller crude oil tankers, being the largest tanker size in the AFRA Freight Rate Assessment Scale Large One Category. AFRA stands for ‘American Freight Rate Association’. Variously reported as being 80,000 to 115,000 tones deadweight. Panamax is the maximum size of oil tanker, with beam restriction of 32.2 meters and length restriction of 275 meters, that can transit the Panama Canal prior to completion of the planned new locks. Typical size is about 55,000–70,000 tonnes deadweight. Handysize/Handymax are typical product tankers of about 35,000–45,000 tonnes deadweight.
Bulk carriers l
l
l
l
Capesize ships that are too large to transit the current Panama Canal and therefore voyage around Cape Horn. All bulk carriers above 80,000 tonnes deadweight fall into this category. Most are up to 170,000 tonnes deadweight but a small number are larger for specific trade routes, the biggest being 365,000 tonnes deadweight. Panamax—As for oil tankers. Handymax ships are between around 35,000 and 60,000 tonnes deadweight. Ships between 10,000 and 35,000 tonnes deadweight have formed the majority of the fleet for many years and are designated ‘Handysize’. In recent years the size of these ships has been increasing and the term ‘Handymax’ has been applied to designate the larger bulk carriers.
14
Sheer forward
Sheer aft
Freeboard Summer load line Amidships
Length between perpendiculars (LBP) Length on waterline (LWL) Length overall (LOA) Aft perpendicular
Ford perpendicular Tumblehome
Camber
Depth Molded beam
Draft
Base line
Rise of floor Half siding of keel
Ship Construction
Figure 2.1 Principal ship dimensions.
Ship dimensions, form, size, or category
15
Container ships l
l
l
l
l
Ultra-large container ships. Ships with a capacity of over 14,000 TEU. Few have been built to date. These ships are too large for any canals. Post-Panamax ships are too large to transit the current Panama Canal and undertake transocean voyages. Their size is typically 5500–8000 TEU though larger ships with over 10,000 TEU capacity have been built. New Panamax ships (including most Post-Panamax ships) would be able to transit the expanded Panama Canal. They may carry up to around 12,000 TEU. Panamax ships that can transit the current Panama Canal carry between 3000 and 5000 TEU. Feeder ships are smaller vessels that do not undertake oceanic voyages but are generally engaged in shipping containers. The smallest of these may only carry several hundred TEU. There is no specific subclass below Panamax size.
IMO oil tanker categories l
l
l
Category 1 (commonly known as Pre-MARPOL tankers) includes oil tankers of 20,000 tonnes deadweight and above carrying crude oil, fuel oil, heavy diesel oil, or lubricating oil as cargo, and of 30,000 tonnes deadweight and above carrying other oils, which do not comply with the requirements for protectively located segregated ballast tanks. These ships have been phased out under IMO regulations. Category 2 (commonly known as MARPOL tankers) includes oil tankers of 20,000 tonnes deadweight and above carrying crude oil, fuel oil, or lubricating oil as cargo, and of 30,000 tonnes deadweight and above carrying other oils, which do comply with the protectively located segregated ballast tank requirements. These ships are due to be phased out. Category 3 includes oil tankers of 5000 tonnes deadweight and above but less than the tonnes deadweight specified for Categories 1 and 2. Also due to be phased out.
Note: For tankers carrying HGO (heavy gas oil) the lower limits for Categories 2 and 3 fall to 600 tonnes deadweight.
Panama canal limits These are set by lock sizes. Current locks are ‘Panamax’. New locks will be larger for ‘New Panamax’ ships (see Table 2.1). Table 2.1 Panama Canal limits
Length (m) Breadth (m) Draft (m)
Panamax ships
New Panamax ships
294.13 32.81 12.04
366 49 15.2
16
Ship Construction
Suez canal limits There are no locks and ship size is limited by the canal dimensions. There is a maximum breadth limit of 75 meters. With no locks the ship length is also unrestricted. The maximum draft is 20 meters. The Saint Lawrence Seaway links the North American Great Lakes to the Atlantic. The limits for ships based on the locks are length 226 m, breadth 24 m, and draft 7.92 m.
Some useful websites www.pancanal.com/eng/general For details of Panama Canal. http://www.suezcanal.gov.eg http://www.greatlakes-seaway.com