The time your ships stay in dry dock totally depends on what work needs to get done on your ship, and your ship size. Dry dock fees are sky-high so most boat owners want the boat to stay in the dry dock for as short as possible.
Why put ships in dry dock?
The main reason that you put ships in dry dock is that you can not work on the part of underwater ships.
The ship’s hull will accumulate barnacles and seaweed after use for several years. The growth of the barnacle will drag the ship and slow its speed, the fuel consumption will increases. It is also unsafe to drive a ship that has never inspected or cleaned its hull.
For safety reasons, passenger ships, and commercial ships are required for periodic checks. Besides hull cleaning and inspection. it is also important to check the propulsion system, rudder and steering mechanism, and other mechanical systems as well.
How many different dry docks?
There are 2 different dry docks: Land-based dry docks and floating dry docks.
Land-based dry docks
Land-based dry docks located on the land with gates. The dry docks will fill with water until the water inside the gate is equal to the water level outside so the ship can be dragged in. Once the ship is positioned inside the dock the gate is closed and the water is pumped out.
When the ship is completely out of the water, the mechanics can walk on gangplanks or walk on the ship deck to fix the ship.
The good part of land-based dry docks is it’s close to the equipment, warehouses, craftsmen, etc. The lacking part of a land-based dry dock is its size limitation. The gate can not close if the ship is larger than the dock.
Floating dry docks
Floating dry docks are movable. You can tow a floating dock to the destination if the dock does not have an engine. A floating dock can sink underwater and move under a ship. When the boat is in position then water is pumped out from the floating dock then the ship is raised above the water.
There is no gate on floating dry docks so floating docks can take ships larger than docks. Some large floating dry docks come in sections like puzzles, which you can combine or detach to fit different sizes of vessels.
Floating dry docks float on water and are not close to land, so it is not close to shops, tools, and workers. Nowadays many more floating dry docks are equipped with onboard cranes, power supplies, and other convenient tools to fit the needs.
What kind of ship have to be put in a dry dock?
Large ships that are over 60 feet long would need to be put in a dry dock to work on their hull, engine, exterior, etc. if the ship is small, you can use a boat crane to lift the ship out from the water and work on the ship in a boat yard.
How often do you need to put ships in dry dock?
The majority of boat owners suggest every 5 years, you need to put your ships in a dry dock to inspect the hull, engine, propulsion system, shaft damage, etc.
Merchant ships might dry dock every two or three years for the hull, and engine inspection. Cruise ships are usually put in dry dock every 5 years. Some ships need to be put in the dry dock because of unexpected underwater damage.
When should you put ships in dry dock?
Most ship owners put their ships in dry dock in winter because they do not use their ships that much in winter. Since the majority of boat owners need dry docks in winter, so the demand for the dry dock is high in the winter season. The high demand creates high prices and less availability.
If you can dry dock your ship in the summertime, you will get a better price and more availability. Very few ship owners want to have work done on their ships in the summer.
How much does the dry dock cost?
The dry dock cost varies greatly on your ship’s size, your ship’s location, and what kind of work needs to get done on your ship. The dry dock is expensive. It is easy to accumulate to a million dollars per day for a large ship.
Large ships cost more than small ships in dry dock. if your ship is located in a busy port such as New York, New Jersey, or Los Angeles, the dry dock fee might cost several times as other small ports.
Here is a sample of some drydock charges in Great Lakes shipyard in 2022.
Drydock/Undock $17,250
Each day on dry dock : $690
Labor charge per hour: $100
Shipyard equipment
Crane service: $290 per hour
Rigging service: $100 per hour
Forklift : $170 per hour
Why dry dock is so expensive?
The land is expensive
Most dry docks are located on expensive, waterfront property, so the land itself is already costly. More and more ships are being built enormous so the dry dock is getting big and big. The bigger the dry dock the more expensive the land.
The labor fee is expensive
The labor cost is always high in the US, especially for skilled laborers. You need skilled laborers to inspect and repair your ships.
The equipment on the dry dock is expensive to use
It is expensive to either use the equipment or rent the equipment. Some equipment is specialized for the vessel such as marine travel lift, crane for boats, Scissor lift, etc.
Related read: Shipyard vs. Dockyard vs. Boatyard
Can you drive a ship into a dry dock?
It is very rarely a ship is driven into a dry dock.
The dock position for a ship is calculated pretty precisely, it is hard to drive a ship in an exact position, so most ships are towed into a drydock.
The dock itself is expensive. Some docks are worth hundreds of million. The dock owners do not want to take the risk of some ships hitting anywhere.
Here is a good video explaining in detail how big the job is of dry docking a ship
Do you turn ships off completely during dry dock?
Most of the time NO. Ships at the dry dock would still have power from the dock, and keep the lights on for workers.
Besides the basic outlet power, most systems will turn off completely at the dry dock. You may not have electrical power, portable water, pumps, or other services on board when the ship is at the dry dock.
How do ships stay upright in a drydock?
The blocks on the dry dock support the vessel and keep it upright when the ship is out of water.
when the ship is towed to the block position, a diver will inspect underwater to make sure each block is in the right position. The vessel’s centerline is in line with the blocks, and the ship is on the blocks.
Most cargo and passenger vessels have flat bottoms, which makes it easy for blocking them upright in the dry dock.
How does one get a ship out of the dry dock?
There are lots of steps to bring ships into the dry dock and get ships out of the dry dock.
A dock master needs to make sure everything underwater is in order before flooding the dry dock.
The steps include filling the ballast, flooding the dock until the ship is floating, disconnecting any shore supply, and dragging the ship out of the dock through several tugboats.
You might also like the below-related articles
How To Dock Your Boat Like A Pro: Stern-In, Bow-In, And Alongside
Displacement vs. Tonnage (Explained)
Choosing The Right Mooring Lines Or Dock Lines For Your Boat
Resources:
www.thegreatlakesgroup.com
