Are you curious about the speed of a cargo ship steaming worldwide? Most of the ships seem to be very slow for people not involved in the industry, but some top speed of the HSC Francisco will impress anyone – 58,1 knots or 107,6 km/h.
However, the average speed of a cargo ship is much lower and that is why they are often considered slow transport. On the other hand, ships move around 90% of the world cargo trade, use direct sea routes and are underway 24 hours a day, and are the most cost-effective transport to move the cargo.
If you’ve ever wondered what is the speed of a cargo ship, why it is so low, and if it is reasonable to build a faster ship, then keep reading. We’ll give you a glimpse into the variety of cargo ships and help you get a better overview of world fleet capabilities and compare ship types by means of speed.
What Defines The Speed Of A Cargo Ship?
The speed of a ship is measured in knots and is an important factor in both the safety of navigation and efficient maritime trading. It determines the ship’s ability to take effective maneuvers to avoid a collision or stopping ability, the time required for the ship to perform its voyage, ETA to a waypoint, or to the port of destination.
The speed of most cargo ships can range from 12 knots to 30 knots which are defined by ship design and main propulsion of the ship. However, the speed of a cargo ship during the voyage depends on several factors like wind direction and speed, the condition of the sea and high waves, the trim of the ship, and whether the vessel is in ballast or loaded.
The reason for the relative slowness of all water transport lies in the resistance of water: it not only keeps the ship afloat but also slows it down.
Moreover, the faster it moves, the more water resists it. To accelerate a ship beyond the notorious 20-30 knots, one must either expend too much energy or make the ship very long and narrow so that it cuts through the water like a knife. But this, in turn, is fraught with a break in the ship on large ocean waves.
Why The Speed Of A Cargo Ship Is Important?
Good speed allows for good handling of the vessel. Bridge officers are able to maneuver the ship wherein the speed required is attained, however, the speed of a cargo ship is one of the most important operational and technical characteristics of a vessel.
The speed of a cargo ship determines its carrying capacity and the speed of cargo delivery and depends mainly on the power of the power plant. The choice of the speed of the vessel during its design by naval architects is a very difficult issue since it cannot be solved without taking into account the fuel consumption of the power plant, the carrying capacity, and the cargo capacity of the vessel.
In practice, the following concepts of the speed of cargo ships are used: maximum and economical speed both in loaded and ballast conditions. Ship speed may be found in ship particulars as it varies even for similar size ships.
The maximum speed of a cargo ship is measured at sea trials in ballast or loaded conditions running through the water with bow-on wind and tide, then turning 180° and the measurement is performed again in opposite direction.
The Eco or economical speed of a cargo ship is the speed of the vessel at which fuel consumption per unit of distance traveled is minimal. Commonly, economical speed is much lower than the technical speed by 20-30% and is used only in cases where it is unprofitable for the vessel to follow at full speed.
For example, if the ship may arrive at the port of destination on non-working days and will have to pay port dues for these days, the loading or discharging berth will be occupied, ship’s ETA is much earlier than required. Sometimes a ship has to follow eco speed if a vessel has an insufficient supply of bunker fuel and cannot reach the port of destination at full speed.
Top speed of a cargo ship
The top speed of a cargo ship would vary from type of ship, weather condition, and if the ship is in laden or ballast condition. Types of a ship involve general cargo, bulk carriers, tankers, car carriers, Ro-Ro, and container ships.
General cargo ships and bulk carriers can have a top speed of about 16 knots. This would mean that wind and current are in favor of the vessel and not against the course and heading of the ship. The ship must also be at even trim or trimmed by the stern to maximize propulsion of the engine.
For supertankers, the maximum speed can reach up to 18 knots while regular-size oil-carrying ships can have a top speed of about 15 knots. This is because of the newer design, more powerful engine, and the vessel at maximum loading capacity with favorable winds and current.
Car carriers on the other hand have a top speed of about 21 knots. Despite the vessel having a high freeboard, most modern PCC(Pure Car Carriers) have aerodynamic designs to help attain maximum speed in the open sea. Though, strong winds and currents can greatly affect the vessel.
Containership has been recorded to achieve a top speed of about 30 knots. Containerships are among the faster cargo ships as this type of ship carries various types of cargo that include time-sensitive goods for end customers and perishable goods.
The cargoes of each containership are commonly delivered to multiple ports hence, the vessel is required to be as fast as possible. Hydrodynamic limits of the hull and engine are designed for optimal cruising speed.
Why are cargo ships so slow?
There are several factors that make cargo ships so slow. This would include the size and weight of the vessel, the weight of the cargo, weather conditions, and forces acting upon the ship.
Though the ship’s engine has become much bigger and more powerful these days, the size of the vessel which involves the length overall and breadth have also increased. Some containerships have an LOA of about 400 meters and 60 meters wide.
Worth mentioning that speed is important for charterers to deliver goods faster, however, it leads to higher consumption of fuel which is one of the primary expenses of running the ship. The faster the cargo ship moves, the more water resists it and more marine fuel is consumed.
A summary of the containership speed and fuel consumption was published by The Geography of Transport Systems that highlights fuel consumption increase primarily with an increase in the speed of a cargo ship.
The weight of the cargo also affects the movement of ships. The biggest container vessel can carry more than 200,000 metric tons of cargo while the largest bulk carriers have a deadweight of about 400,000 tons. This amount of cargo has a great impact on the speed and movement of vessels.
Weather conditions also contribute to the movement of vessels being so slow. It is true that when wind and current are favorable, ships can reach maximum speed. However if both wind and current are against the heading, it can reduce the speed of the vessel. Notable currents are the Kuroshio, Californian, East Australian, and the Agulhas current.
Other forces acting on the ships result in slower movement of the vessel. The drag and friction of the ship against the water can restrict the movement of the vessel. Appendage resistance includes all underwater appendages such as propeller, shaft, struts, rudder, and bilge keels.
The average speed of a cargo ships
Over time the shipping industry set its standards in maritime transport for ship sizes, capacity, fuel consumption, and of course the speed of a cargo ship. Various types of ships have their average speed typical for the industry, but may be lower or higher depending on owners’ special requirements.
Here is the table of the average speeds of various types:
|Type of ships||Average speed|
|Mini bulkers||8 – 13 knots|
|Small bulkers||10 – 15 knots|
|Oil tankers||9 – 15 knots|
|Chemical tankers||12 – 17 knots|
|Feeder container ships||13 – 20 knots|
|Container ships||14 – 20 knots|
|Bulk carriers||8 – 14 knots|
|Car carriers||13 – 18 knots|
|Ro-ro cargo ships||12 – 16 knots|
|Gas carriers||9 – 15 knots|
How fast does an empty cargo ship travel?
An empty cargo ship, sometimes called in ballast condition, can get to maximum speed faster compared to when it is loaded in full condition. This is because, at times, the cargo weight adds pressure to the engine and propeller, resulting in a slower reaction during maneuvering.
The speed of a cargo ship however of any empty cargo ship would range from 12-16 knots for bulk carriers. Oil and chemical tankers can reach up to 17 knots when in ballast condition. The PCC (Pure Car Carrier) can reach a maximum speed of about 22 knots with favorable winds and currents. At the same time, container ships will have a top speed of about 25 knots.
Ballast and loaded condition cargo ships will have very similar speeds. This is because the physics of traveling through the water sets a maximum speed determined by the length of the ship. When the vessel reaches top speed, all the extra power of the engine goes into making the bow and stern wave bigger, without increasing the speed.
How fast are cargo ships compared to other ships?
Though cargo ships can travel at a faster speed at times, there are other types of vessels that can be slower or faster. The cruise ships and ferries will have similar speeds as other cargo ships.
They can attain 20-25 knots and do so with ease because of their maneuverability and sizes. Most cruise ships have thrusters that assist the vessel during the maneuver. They also carry light cargoes so could be considered cargo ships as well, but still, passengers are their primary focus.
The fastest ship in the world is HSC Francisco with the ability to reach a top speed of 58.1 knots. This passenger ferry is powered by two GE LM2500 gas turbines with water jets and as serving the ferry route between Buenos Aires and Montevideo.
Battleships on the other hand can reach more than 30 knots. USS New Jersey is the official Guinness World Record holder for doing a top speed for battleships of about 35 knots. She is also able to maneuver with ease and can reach maximum propulsion faster compared to cargo ships.
Sailing ships and tug boats are much slower and smaller in size compared to cargo vessels. Most sailboats cruise at a speed of about 4-6 knots while racing yachts can reach up to 15 knots because of their size and bigger engine. The cruising speed of mega yachts can reach more than 30 knots.
Tugs or tug boats which are normally used to assist cargo ships in docking and undocking maneuver can be very powerful. They are also used to push and pull barges that carry equipment and bulk cargoes. The average speed of harbor tugs is generally 8-15 knots while those that navigate in the open seas can reach up to 20 knots.