Deck cargo and flat-top barges are rectangular pontoons with a flat, reinforced deck. Common sizes in Indonesia range from 180 to 330 ft. Barges are towed or pushed by a tug, so their operating limits are set jointly by the barge, the tug, the route and the weather forecast.
Because breadth is large relative to draft, barges have a high initial GM. Freeboard, however, is small, so deck edge immersion comes early and tall deck cargo with a large wind area can erode the stability reserve. Tall, heavy cargo such as transformers, modules or excavators on stools needs careful calculation.
A good barge plan puts cargo on strong deck zones, keeps the combined centre of gravity close to the centreline, leaves access for lashing and towing gear, and gives a slight trim by the stern so the barge tows with better directional stability.
Typical sizes & characteristics
| Parameter | Typical range |
|---|---|
| Common length | 180–330 ft (~55–100 m) |
| Breadth | ~50–100 ft (~15–30 m), increasing with length |
| Depth | ~11–20 ft (~3.4–6 m) |
| Full load draft | ~2.5–5 m, per assigned freeboard |
| Cargo capacity | Hundreds up to ~12,000 t; a 300 ft coal barge is often quoted at ~7,000–8,000 t |
| Deck strength | Varies by barge and zone (often ~5–15 t/m²); use values from construction drawings |
| Propulsion | None; towed or pushed by a tug |
Typical ranges for the vessel class, not data for any specific ship. For planning, use your vessel’s stability booklet and capacity plan.
Cargo spaces & how they are modelled
Deck zones
The deck is modelled as a scaled 2D plan split into zones by the structure below, for example over longitudinal bulkheads and web frames that are stronger.
Side boards
Bulk barges have side boards to contain the heap. Board height limits pile height and affects the wind area.
Below-deck compartments
Watertight spaces under the deck, some usable for ballast. Their contents affect trim and damage stability.
Towing and access areas
Bridle, towing brackets, bollards and access routes must stay clear of cargo so the tug and crew can work safely.
General stowage rules
Deck and point loads
Load per m² in each zone must not exceed the deck limit. Cargo with small feet or tracks sits on grillage or dunnage to spread the load.
Combined centre of gravity
The combined CoG is kept near the centreline to avoid static heel. Heavy pieces go amidships, and tall cargo is checked against the allowable KG.
Trim under tow
Barges are usually set with a slight trim by the stern. Trim by the head makes the barge yaw and wets the forward deck.
Sea-fastening
Cargo is secured with chains, wires or welded stoppers designed for the route accelerations. Designs for high-value cargo are usually reviewed by a marine warranty surveyor.
Freeboard and wind
Draft must never pass the load line. The wind area of tall cargo is included in the stability criteria, especially on open-sea routes.
Common mistakes & risks
- Heavy cargo on weak deck zones without grillage, causing deck plating to deflect.
- Combined CoG off to one side so the barge lists before departure.
- Trim by the head that makes the barge hard to tow and floods the forward deck.
- Sea-fastening designed for sheltered water then used on an open-sea route.
- Tall cargo with a large wind area eroding the stability reserve.
- Cargo blocking access to the bridle, bollards or emergency equipment.
Frequently asked questions
What deck load is safe for a 300 ft barge?
There is no single number. Deck strength depends on plate thickness, frame spacing and the bulkheads below, and differs between zones. Use values from the construction drawings or yard data, and check point loads separately.
Why can a barge with a high GM still capsize?
GM only describes stability at small angles. With low freeboard the deck edge immerses early and the GZ lever falls away, so tall cargo, strong wind or water on deck can exceed the stability reserve.
Can STOWAGE.ID output serve as the official stability calculation?
No. Results are shore-side planning and decision support. The barge’s stability booklet and any class-approved loading computer remain the official reference, as does the marine warranty surveyor’s approval.
Is the Barge Planner available?
Yes, Barge and LCT are in the first wave because they are the most common in Indonesia. The free barge capacity and deck load calculators can also be used for estimates.
Shore-side planning & decision support. The class-approved onboard loading computer remains the official reference.