Overview of shipbuilding
A shipyard is a place where ships are built and repaired. Building a ship is a long job with many teams. The main steps are: layout (the plan), fabrication (cutting and bending steel), assembly (joining plates into blocks), erection (joining blocks into the hull), launching, and outfitting and painting.
A ship is too big to build as one piece. So builders make it in many small parts, and join them in order. Small parts are easier to weld, easier to move with a crane, and many teams can work at the same time.
Most large ships are made of steel plates, which are joined by welding. Welding melts the edge of two metal pieces with a very hot arc, so they become one piece when cooled.
Layout, fabrication and assembly
Layout means turning the designer's drawings into the real shape of each plate. In the past, the full-size drawing was marked on a large floor. Today, computers do this and send the shapes straight to the cutting machines.
Fabrication means working the steel. Plates are cut with a hot flame or plasma torch. Some plates are bent into curves for the bow and the sides. Long steel bars (stiffeners) are cut and shaped too. Every piece is marked with a code, so workers know where it goes.
Assembly means joining the pieces into bigger parts. Plates and stiffeners are welded into flat panels. Panels are welded into blocks. A block can weigh tens or hundreds of tonnes. It is best to build and check each block on the ground, where it is easy and safe to work.
Fitting blocks together and launching
Erection (also called block joining) is the step where a crane lifts each block and puts it in place on a slipway or in a building dock. The edges are lined up exactly and then welded. The welds are checked, so they do not leak and do not crack.
Launching is the day when the hull first meets water. On a slipway, the hull slides down a sloping track into the water on greased ways or on a cradle. In a building dock, the dock is simply filled with water until the hull floats. Launching is a careful job: the hull must slide and float safely and not hit anything.
At launch the ship is not finished. It is a hull with some of its equipment. It is still floating at a draft that is smaller than its final draft, because many things have not been added yet.
Outfitting and painting
Outfitting means fitting everything the ship needs to work: engines, shafts and propeller, pumps, pipes, electric cables, cabins, kitchens, navigation instruments, anchors, winches and lifesaving gear. Much of this work is done while the ship is afloat at a quay. Doing as much outfitting as possible early, on blocks, is easier than working inside a finished hull.
Painting protects steel from rust. Steel parts are first cleaned by blasting. Then coats are applied: a primer, then middle coats, then the top colour. The bottom of the hull gets a special anti-fouling paint that stops shells and weed from growing on it, because growth would increase resistance.
At the end the ship is tested at sea. These sea trials check speed, steering, engine and safety equipment before it is handed to the owner.
Try it
At home: make a paper boat or a cardboard box model in three or four "blocks" (front, middle, back). Join the blocks with tape and see how much easier it is to make small parts than one big one.
In the 3D: drag the Stage slider from left to right. Say aloud what changes at each stage. At the end pick a paint colour.
Key formulas and definitions
- Order of work: Layout → Cutting and bending → Assembly (blocks) → Erection → Launch → Outfitting → Painting → Sea trials
- Welding: two steel parts joined by melting their edges
- Block = several panels welded together; ship hull = blocks joined together
Worked examples
1. Why do shipbuilders build blocks on the ground and not build the hull plate by plate on the slipway?
Many teams can work at the same time on different blocks, welding is easier and safer at ground level, and the slipway is free for the blocks that are ready. This saves a lot of time.
2. Put in order: launch, cut plates, join blocks, make the plan.
Make the plan, cut plates, join blocks (after blocks are made), launch.
3. Why is the bottom of a ship painted with a special paint?
Anti-fouling paint stops shells and weed from growing on the hull. Growth would make the hull rough and the resistance larger, so the ship would use more fuel.
4. A shipyard wants to add a pipe system to a part of the ship. Should it do this before or after joining the blocks if possible? Why?
Before, if possible. A block lying open on the ground is easy to reach with tools and cranes. Inside a finished hull it is tight and hard to reach.
Common mistakes
- Thinking a ship is built as one piece. It is built as blocks and joined.
- Thinking launching means the ship is finished. After launch, the engines, cabins and equipment are still being fitted.
- Mixing up fabrication (cutting and bending parts) and assembly (joining parts).
- Thinking paint is only for beauty. Paint stops rust, and the bottom paint also reduces growth that slows the ship.