Feeder ships in Indonesia rarely sail one port to one port. A rotation such as Surabaya → Makassar → Balikpapan → Tarakan means discharging and loading at every call. The plan made at the first port already has to think about the next ones: where new cargo will go, how to avoid restows and whether the ship will still comply when it sails from each port.
What changes on a multi-port rotation
On a single-destination voyage the planner deals with one departure condition and one arrival condition. On a multi-port rotation there is a departure condition for every leg, and each one depends on decisions taken at earlier ports. Three things have to be managed together:
- The port of discharge (POD) sequence, so every box can be discharged without moving another.
- Room for cargo still to come, both slots and weight capacity, at mid-rotation ports.
- The ship's condition on every leg: stability, trim, draught, longitudinal strength, visibility and lashing.
POD sequencing: tiers, bays and hatch covers
The basic rule is simple: whatever comes off first must be reachable first. In practice it works at three levels.
| Level | Rule | Consequence if broken |
|---|---|---|
| Within a stack | Earlier POD above later POD | Restow of the boxes on top |
| Deck vs hold | Deck cargo for the same or an earlier POD than the hold cargo below | All deck cargo on that hatch cover must be shifted and the cover lifted |
| Between bays | POD bay blocks spread fore and aft | One port's discharge swings trim and strength to extremes |
Many feeder planners allocate bay blocks per POD: one or more complete bays (hold and deck) for a single port. Bays emptied by discharge can then be refilled with new cargo without clashing with the POD sequence. Combine this with tier separation inside bays for the remaining cargo. Reading slot positions is covered in container ship bay planning.
Forecast bookings and reserved slots
When the ship leaves Surabaya, cargo to be loaded at Makassar or Balikpapan is usually only a forecast from the commercial team. The planner needs to reserve:
- Slots in the right places, for example the top tiers of the Tarakan block for Makassar cargo bound for Tarakan, and the bays that will be emptied by discharge for cargo bound back to Surabaya.
- Weight capacity, because an empty slot cannot always be used if the box is heavy. Stack weight limits and stability can leave slots unusable.
- Special slots: reefer plugs, dangerous goods positions that respect segregation, and positions for out of gauge cargo.
Forecasts are nearly always off. Use a realistic average weight from the route's history, add a margin, and update the plan as soon as the final load list and VGM data arrive.
Domestic rotation example (illustrative vessel)
A fictional 500 TEU feeder runs Surabaya (SUB) → Makassar (MKS) → Balikpapan (BPN) → Tarakan (TRK) → back to Surabaya. All figures are illustrative.
| Leg (departing) | Discharge | Load | On board at departure | Check focus |
|---|---|---|---|---|
| SUB → MKS | — | MKS 180 TEU (2,300 t), BPN 140 TEU (1,750 t), TRK 90 TEU (1,050 t) | 410 TEU, 5,100 t | Deepest draught, longitudinal strength, reserved slots for MKS and BPN |
| MKS → BPN | MKS 180 TEU (2,300 t) | BPN 30 TEU (300 t), TRK 20 TEU (240 t), SUB 60 TEU (450 t) | 340 TEU, 3,790 t | Trim change once the MKS block is empty, GM up or down |
| BPN → TRK | BPN 170 TEU (2,050 t) | TRK 25 TEU (280 t), SUB 120 TEU (1,100 t) | 315 TEU, 3,120 t | No SUB boxes on top of TRK boxes |
| TRK → SUB | TRK 135 TEU (1,570 t) | SUB 80 TEU (700 t) | 260 TEU, 2,250 t | Light ship: ballast, trim, propeller immersion, visibility |
Check that the numbers carry through: departing Makassar = 5,100 − 2,300 + 990 = 3,790 t; Balikpapan = 3,790 − 2,050 + 1,380 = 3,120 t; Tarakan = 3,120 − 1,570 + 700 = 2,250 t. Distances and passage times between ports can be estimated with the port distance calculator and the voyage planner.
Some decisions that fall out of this example:
- The MKS block (180 TEU) should be split between forward and aft bays. If it all sits forward, discharging at Makassar leaves the ship sharply trimmed by the stern.
- Surabaya cargo loaded at Makassar (60 TEU) goes into the bays vacated by the MKS block. Tarakan cargo from Makassar (20 TEU) goes into the top tiers of the TRK block reserved since Surabaya.
- At Balikpapan, the Surabaya cargo (120 TEU) goes into the bays vacated by the BPN block, not on top of Tarakan boxes.
- The last leg is the lightest condition, with many empties. It is often the most critical for trim, propeller immersion and bridge visibility.
Stability on every leg after cargo work
Every discharge and load moves the ship's centre of gravity. Discharging low hold cargo raises the KG of what remains and can reduce GM. Discharging high deck cargo lowers KG and increases GM. Too much GM is a problem as well: the ship becomes stiff, rolls quickly and the forces on deck container lashings rise. So the planner calculates GM for every departure condition, not just Surabaya. GM is explained in metacentric height (GM) explained.
Other per-leg factors to check:
- Fuel and fresh water are consumed on passage, changing trim and free surface.
- Ballast is adjusted at each port, including any ballast water management rules that apply.
- Draught limits for channels and berths at each port, from the port authority and terminal.
- Longitudinal strength once a bay block is empty, because the weight distribution changes sharply.
The link with restows and data exchange
Poor multi-port planning is a leading cause of restows. The guide to container restows and how to reduce them covers restow types and their cost. After each port, the updated plan goes to the next terminal as a BAPLIE message, which you can inspect with the BAPLIE viewer.
Where planning software fits
STOWAGE.ID Vessel Stowage can simulate a port rotation, show the departure condition of every leg and flag POD sequence breaches before the ship arrives. It is a shore-side planning and decision-support tool. The official reference remains the vessel's class-approved loading computer and stability booklet, with the chief officer's and master's approval at every port. For the wider container ship workflow, see container ship stowage.