Reference
Panamax
Sized to the original canal locks. What it carries, how it is built and the limits that define the class.
- Typical deadweight
- Typically about 65,000–80,000 DWT
- Length overall
- Maximum 294.13 m
- Beam
- Maximum 32.31 m; typically about 32.26 m
- Draft
- Maximum 12.04 m in tropical fresh water
- Defining constraint
- The original Panama Canal locks
- Cargo gear
- Usually gearless
- Typical draught
- About 14.1 m at full load, above the canal transit limit
- Cargo holds
- 7
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 Panamax vessels
The class defined by the original Panama Canal locks, which for most of the twentieth century set the largest ship that could pass between the Atlantic and the Pacific without rounding South America.
The limits are precise: 294.13 metres length overall, 32.31 metres beam and 12.04 metres draft in tropical fresh water. Ships were built right up to those figures, and the beam limit in particular shaped the hull form of an entire generation of bulk carriers.
The larger Neopanamax locks opened in 2016 and relaxed the constraint considerably, but Panamax remains a distinct and heavily traded size class in its own right.
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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