Reference
Coaster
Short-sea and river-sea trading. What it carries, how it is built and the limits that define the class.
- Typical deadweight
- Typically under 10,000 DWT
- Length overall
- Commonly under 120 m
- Defining constraint
- Shallow-draft ports, rivers and canal systems
- Cargo gear
- Geared
- Typical trade
- Short-sea and regional
- Cargo holds
- Commonly 5 or fewer
Size class names such as Handysize, Supramax and Capesize are commercial conventions rather than formal standards, and the deadweight bands attached to them vary between brokers, exchanges and shipowners. The canal and berth limits quoted below are published dimensions and are exact; the deadweight ranges are indicative.
About coasters
The smallest ships in the dry cargo trades, built for short-sea and river-sea work rather than ocean crossings.
Their value is access. Shallow draft, modest length and often a lowerable wheelhouse and folding masts let them reach inland river ports, canal systems and small harbours that no ocean-going ship could enter.
Many are ice-strengthened for Baltic and northern European winter trading, and they typically carry their own gear because the ports they serve rarely have cranes.
What it carries
How it is built
- A single-deck hull divided into large cargo holds, closed by weathertight steel hatch covers that roll or fold clear for grab and conveyor work.
- Ballast tanks in the double bottom and in the topside and hopper wings, which shape the hold and let the cargo self-trim as it settles.
- Corrugated transverse bulkheads between holds, stiff enough to take the pressure of a dense cargo without intermediate framing inside the space.
- Machinery and accommodation aft, leaving the full forward length of the ship for cargo.
- On geared ships, deck cranes or derricks between the hatches so the vessel can work in ports with no shore equipment.
Why it is used
- The cheapest way to move a tonne of dry commodity, because the cargo needs no packaging, unitisation or securing.
- Loading and discharge rates are very high where shore equipment is good — grabs, conveyors and shiploaders move thousands of tonnes an hour.
- Geared ships can trade almost anywhere, including ports with no cranes of their own.
- Hold arrangements are flexible enough to carry several parcels of different commodities on one voyage.
What to check before fixing
- Dense cargoes such as iron ore load the structure heavily and are subject to strict loading sequences to avoid overstressing the hull.
- Cargoes that can liquefy — some ore concentrates and fines — must be checked against their transportable moisture limit before loading.
- Draft and air draft govern which berths and waterways a ship can use, and both change with the season and the fresh-water allowance.
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