Cruise Ship Anchors: Everything You Need to Know
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Today’s massive cruise ships are some of the most technologically advanced vehicles on the planet. Yet, they still use the ancient invention, anchors.
You’d think that an invention dating back to 592 BC is out of the window, but anchors still play an essential role for cruise ships.
This article will show you everything you need to know about cruise ship anchors. We’ll compare them to the modern ship stabilizing thrusters, and we’ll also compare the size and weight of one of the most famous ships in the world.
Cruise ships use anchors to hold the ship in place. Cruise ship anchors are commonly used in tender ports, where the ship cannot moor to a land-based dock.
The first known use of ship anchors dates back to Ancient Greece, around 592 BC.
Despite advances in technology, cruise ship anchors remain essential in ship construction.
Modern ships have advanced positioning systems that keep them in place using engines and thrusters. This allows ships to remain in place without drifting.
The technology uses GPS and the cruise ship’s engines to keep the vessel stationary and counter the ocean currents and waves.
Dynamic positioning systems are commonly used when ships must remain in deep water, where an anchor may not be long enough. While the chain length limits the use of anchors, the dynamic positioning systems don’t have any limitations. They can be used in water of any depth and are often used to keep ships positioned in the deep ocean.
They also pose less risk to coral reefs, where an anchor might disturb the reef.
Despite the advantages of dynamic positioning systems, the new technology doesn’t eliminate the need for anchors.
Ship stabilizing thrusters consume fuel and are liable to malfunction and damage. While they don’t impact coral reefs like the anchor, burning fuel has its own environmental impact.
On the other hand, anchors are much more economical when keeping the ship in place since they consume no fuel.
Cruise ship anchors work by extending down to the seabed of shallow water and using their weight to hold the ship in position.
Anchors rest against the sea bed and utilize their heavy weight to keep the ship stationary. They counter the effect of currents and waves, holding the ship in its position.
Utilizing the sea bed is why cruise ships can’t rely on anchors in deep or open water. These anchors’ chains have a limited length; if the anchor can’t reach the sea bed, it can’t perform its function.
Cruise ship anchors range between 10–20 feet long and average 8–15 feet wide. An anchor’s size is directly proportional to the size of the vessel.
Larger and heavier ships require larger and heavier anchors.
The Titanic had an 18 foot 6 inches long main anchor, and it was the largest anchor made at the time.
Let’s not forget about the chains that hold these anchors. These chains have various lengths and thicknesses. The chains’ length depends on the anchor they’re supposed to carry, and the thickness depends on the ship they’re supposed to hold.
The average weight of cruise ship anchors ranges between 10–20 US tons. The weight can go considerably higher to accommodate the largest ships. However, it’s unlikely to go lower because it would be difficult for it to stabilize a ship with a lower weight.
The Titanic had an anchor that weighed around 16 US tons. Even back then, that was mighty impressive.
Despite the anchor’s weight, it merely acts as a point of contact with the seabed. The anchor’s chain is far heavier and vital in keeping the ship stationary.
Nautical engineers use various methods to calculate the chain length. Generally, heavier anchors require heavier chains.
The weight of the chain helps hold the cruise ship in place.
Longer chains can withstand more movement, unlike short chains, which can cause the anchor to lose contact with the seabed during rough seas.
When an anchor is lowered into the ocean, sufficient slack must be in the chain, which rests on the seabed. The slack provides a greater surface area of contact with the seabed, which absorbs more movement.
Here’s a sample table to show you the correlation between the lengths of chains based on their anchors’ weight.
Remember that we’ll use US tons, which are slightly lighter than metric tons. 1 US ton is around 907 kg.
|0.7 US tons
|4.7 US tons
|22 US tons
|51 US tons
Regarding thickness, there are three primary sizes of chains.
Most modern cruise ships have two anchors, with one on the port side and the other on the ship’s starboard side.
Cruise ships occasionally use both anchors if the waters are rough or there’s a strong current. Most of the time, however, the cruise ship uses only one anchor and keeps the other one for backup.
Some larger cruise ships are equipped with a third backup anchor. The third anchor is often smaller and weighs less than the primary two anchors. It’s primarily used as a backup if one of the primary anchors breaks or malfunctions.
It’s unlikely for a modern cruise ship to lose its anchors. Many cruise ships also have two anchors. So, if one becomes unusable for some reason, the second will act as backup.
If, for some reason, the ship loses all functioning anchors; it can still rely on its thrusters to keep it stable.
In the improbable scenario that both the anchors and dynamic positioning systems also get damaged, the cruise ship will be at the mercy of the moving water as long as it’s not sailing.
In other words, the cruise ship could still get from point A to point B, but it won’t manage to stay idle without anchors or dynamic positioning systems.
The only solution would be to dock and have the issues repaired.
Cruise ships generally avoid using the anchor due to the environmental impact on coral reefs and the seabed.
But dropping anchor also impacts guests.
Staterooms located near the ship’s bow are some of the worst on a cruise ship. One reason is the sound of the chain when the ship drops anchor.
Cruise ships often arrive at ports of call in the early morning. And no guest wants to be woken by what sounds like a freight train at 5 am while the ship drops anchor.
So what do cruise ships do instead?
Some cruise ports, such as Labedee, Haiti, offer fixed mooring points. The mooring points allow ships to remain stationary at sea within a reasonable distance of the port. This allows the vessel to remain idle without using the anchor.
If no fixed mooring points are available, some cruise lines will opt to use dynamic positioning systems to keep the ship idle using the ship’s engines. The bridge simply inputs the coordinates, and the system takes care of the rest.
But, dynamic positioning systems come at a cost.
They require significant amounts of fuel to power the engines. Not only are fuel costs a primary consideration for cruise lines, but they also impact the environment.
Some cruise ports have local laws prohibiting the use of anchors to protect coral reefs. But if there are no laws regarding anchors, it’s up to the captain to decide whether to use the dynamic positioning system or drop anchor.
Below is a visible of the cruise ship Island Princess dropping anchor.
Cruise ships are built with impressive engineering and enriched with fantastic technology, but they’re still humble enough to remain loyal to their anchors.
Anchors excel in stabilizing large cruise ships in shallow waters as long as they’re heavy enough to do the job. They’re also a great backup solution if modern positioning systems cease to function for any reason.
However, anchors can only work if their chains are long enough for them to reach the seabed, rendering them useless in open water.