Ship Wreck: BOS 400 Off the South African Coast

BOS 400 was a French derrick and lay barge that ran aground on the South African coast on June 26, 1994, while under tow. The loss followed the breaking of her tow-cable in heavy weather, and the barge was never recovered as a working vessel.

Construction and Design of the BOS 400

Barges of this kind were flat-bottomed, box-shaped hulls built to carry heavy lifting equipment and work from a fixed position at sea. A derrick or lay barge carries a crane or derrick on deck for lifting and placing loads, and often lays pipe or moors other vessels. Because such a barge has a large deck area and relatively little draught, it sits high and catches a great deal of wind. Its stability depends on how the ballast, the lifting gear and the cargo are arranged.

Vessels of this type are generally built from steel plate, with transverse frames, longitudinal stiffeners and watertight compartments below the deck. Steel gives strength and a long working life, but it corrodes if coatings fail, and cracks can grow in areas of stress such as around crane foundations. Designers therefore pay close attention to the strength of the deck and the connections under the lifting equipment.

Towage From Pointe-Noire and the Breaking of the Cable

The Russian tugboat Tigr was chartered to tow the barge from Pointe-Noire in the Republic of Congo to Cape Town in South Africa. The tow was a long passage along the western coast of Africa, where the weather can change quickly. On the final stage the tow-cable broke during a force 9 northwesterly gale. Without the tug’s pull, the barge lost her steering and was driven toward the land.

The barge ran aground off Duiker Point near Sandy Bay. The source records that this was the same place where the earlier wreck of the SS Oakburn had lain. Few details of the handling in the final hours are recorded, so the exact sequence of the cable parting is not clear.

The Loss of the BOS 400 From a Naval Architect’s Viewpoint

This analysis describes how losses of this kind commonly happen and is not a statement about what happened aboard this particular barge. A vessel of this type loses control once the tow parts, because a barge with no way on has little ability to hold a course. Her large flat sides and high deck give the wind a big area to push against, which causes leeway, the sideways drift that carries a drifting hull toward a lee shore.

A barge that is driven onto a rocky coast generally suffers damage to the bottom plating in the forward or aft sections. Water enters the compartments one after another, and as they fill the vessel loses buoyancy and stability. A heavy lifting gear on deck raises the centre of gravity, so a ship in this condition can heel further than expected, which makes further damage more likely.

Towing creates its own risks. The tow line must be sized, rigged and inspected for the forces of the sea, and a parted line can snap back dangerously across the deck. Cable and bridle arrangements that spread the load help, but a single weakness in the chain of gear can end the tow. In shallow water near the coast, breaking seas can also steepen and break over the hull, adding to the forces on the barge.

Groundings on rock and reef usually give a more lasting result than groundings on sand. Once a steel hull is holed on a hard bottom, it is difficult to hold the vessel in position, and the surf keeps working the hull. These general mechanisms help explain why a barge that loses its tow close to a lee shore in a gale can become a total loss.

Reducing the Risk of Losses Like That of the BOS 400

These are general measures and not a claim that this particular tow lacked any of them. Good seamanship begins with reading the weather early and planning the passage to keep sea room from the coast. A tow that is driven toward land in a gale has few options, so an early decision to shelter or change course can matter a great deal. Keeping well clear of the shore at night and in poor visibility is another basic safeguard.

Equipment and preparation also reduce risk. Towing gear should be properly sized, inspected before the voyage and provided with a back-up arrangement where possible. Ground tackle, anchors and a serviceable tug or second tug can help hold a disabled vessel away from danger. Watertight subdivision, tight hatches and secure stowage of deck cargo improve survival if the hull is damaged. Modern towing and salvage vessels use satellite positioning, radar, forecasts and better tow monitoring, which give crews earlier warning than was once common.

Aftermath, Salvage and the Wreck Today

Several attempts were made to tow the barge off, but salvors were able to recover little from the wreck, and it was treated as a total loss. The barge remains where she grounded, with a large crane and part of the superstructure still visible above the water. The source records that the wreck is slowly disintegrating under the action of the sea.

The tug Tigr was built in 1987 in Polish shipyards. After the accident she remained idle in the Cape Town docks from 1994 to 2000, when she was sold for $625,000. Her later history is a separate matter from the barge’s loss, but the two events are linked by the tow and the chartered voyage.

Plain-English Terms

• Derrick means a lifting crane or boom used to raise and place heavy loads on a ship or barge.
• Lee shore means land that the wind is blowing toward, so a vessel that cannot sail clear of it risks being driven aground.
• Leeway means the sideways drift of a vessel pushed by wind or current away from her intended course.
• Tow-cable means the heavy line used by a tug to pull another vessel, which can part under strain.