The Challenge of Simultaneously Navigating Multiple Ocean Barges

The opening of the super port at Colombo, Sri Lanka presents a challenge to maritime researchers as the largest container ships afloat begin to call at the Port of Colombo. There would be economic benefit to developing a technology capable simultaneously moving multiple oceanic barges between India’s offshore super port and multiple shallow-draft ports located around India’s coast. So far, articulated tug-barges involve a single tug pushing and navigating a single ocean barge. Perhaps there may be scope to further develop the concept to involve a twin-hull catamaran tug capable of pushing and navigating a pair of ocean barges.

Twin-Hull Tug:

It is technically possible to develop a twin-hull catamaran style of tug with coupling bumpers built into each of the twin hulls, to allow it to couple to 2-barges. The twin hulls may need to include a spring-loaded pivot mechanism or hinge to allow each hull some roll freedom. A concentric pair of large-diameter, hollow cylinders may form the structural basis of such a hinge, with bearings capable of carrying extreme axial-thrust loadings, like the long-proven thrust bearing technology applied to ship propeller shafts. The hinge technology would also need to withstand extreme bending loads.

The double and/or triple coupling bumpers between tug and barges would allow for relative pitch motions between the tug and barges when sailing across ocean. It would also be essential for the design to keep the 2-barges parallel to each other. Any non-parallel misalignment between the barges would impose an extreme bending stress across the tug superstructure. A directional stabilizer designed for installation between the bows of the 2-barges could assist in maintaining parallel barge alignment, with scope for other technology to minimize relative roll between each hull.

Lateral Truss Coupling:

A multi-triangle truss structure with some twisting flexibility may connect across and link between the stern of the 2-barges to limit relative roll. The torsion (twist) flexibility would allow relative pitch motions between barges and also between tug and barges. A directional stabilizer (or restraint) located near the bows of the barges could help keep the barges parallel to each other while sailing through ocean swells. A removable (or retractable) cross-link secured between parallel twin barges would allow them sail more like a twin-hull catamaran, reducing structural stresses that misaligned twin-barges would otherwise impose on the lateral superstructure of a twin-hull tug.

There may be scope to design a horizontal triangular truss into the section of tug that connects the 2-hulls, with sufficient structural strength to withstand the tension and compression loads that would result from navigating 2 x 50-ft wide barges of 250 to 500-ft length across open sea. When at port, there would be need to either temporarily remove or fold the truss structures so as to ease the loading and unloading of cargo. A single crew may navigate a twin-hull tug simultaneously moving 2-barges across ocean at lower cost than 2 x separate crews on 2-tug-barge assemblies.

Triple (Tripod) Hull Tug:

A narrow non-buoyant central structure that exceeds the length of a barge would connect a forward single hull to a pair of twin rear hulls. The forward hull would couple to a single barge while wide spread rear hulls would each couple to a barge. All of the 3-hulls would have some freedom of roll, with parallel coupling bumpers allowing relative pitch freedom while also providing steering/navigational stability. The central structure would be designed to withstand extreme bending loads to allow the tug to steer and navigate the forward barge.

A mechanical linkage installed between the stern of the forward hull and each bow of the pair of trailing barges would maintain parallel alignment to the central structure. While a triple hull tug concept would require extensive further research and scale-model testing, it offers the prospect of a single crew simultaneously navigating 3-barges across ocean, with the fuel consumption of 2-barges. Alternatively, a non-powered tripod-hull structure tug with twin rear hulls with V-notch sterns could be coupled to 3-barges with V-notch sterns. A twin-hull tug would couple to the stern of the assembly to push and navigate it across ocean.

Quad-Hull: 

A tripod-hull tug would serve as the basis by which to develop a quad-hull non-powered floating structure, to which a twin-hull tug may couple to push and navigate it. Alternatively, the quad-hull floating structure may be a tug, with an extended length narrow central structure linking the forward and rear catamaran hulls. The non-buoyant central structure would be designed to withstand extreme bending loads. Concentric large-diameter metal tubes at the forward catamaran cross member would allow for relative roll between the forward and rear catamarans. The 4-hulls would include coupling bumpers that couple to, push and navigate oceanic barges.

A single crew may feasibly navigate 4-barges across ocean between a central seaport and the mouth of a navigable river. Upon arrival at the closest accessible river, the barges would be coupled to each other so as to allow conventional tugs to push and navigate them upstream to inland ports. A quad-hull could help move 4-barges between the Port of Istanbul and the mouth of the Danube River, between the Port of Montreal and Gulf of St Lawrence super ports at Sydney or Strait of Canso, also between these super ports and several East Coast American ports.

Economics:

A twin-hull catamaran tug designed with the option to expand to 3 and 4-hull capability would allow a single crew to navigate 2, 3 or 4-laden barges at competitive costs to single mono-hull tugs each navigating a single barge. When pushing 3 or 4-barges, the tug with multi-barge capability may consume a little more fuel than 2-tugs each pushing a barge across ocean. Sailing along inland waterways allows for barges to be tied/coupled to each other lengthwise and widthwise, except that such assemblies can only sail on relatively calm waters.

The relatively low wave amplitudes that occur on the Gulf of St Lawrence may be the maximum possible wave amplitude for assemblies of barges that are directly coupled to each other. Except that such assembles of barges may be unsuitable for sailing conditions on comparatively small and enclosed bodies of water such as the Black Sea, Baltic Sea, Red Sea, Persian Gulf, Irish Sea, Adriatic Sea, Southern Mediterranean Sea and several inland lakes. A twin-hull tug that could expand to 4 and 4-hull options may be more capable of simultaneously sailing multiple barges across open ocean.

Precedents:

There are precedents of laterally connecting mono-hull vessels into twin hull vessels to improve ocean sailing capability. While wind/sail powered twin-hull vessel assemblies date back over 1,000-years, the first propeller powered twin-hull catamaran vessels sailed during the early 20th century. While the twin-hull design has proven popular for numerous passenger and boat racing applications, changing and evolving freight market conditions may be creating an application for a twin-hull tug capable of simultaneously pushing and navigation a pair of identical barges. An earlier article by this research did mention the possibility of a twin-hull catamaran tug for a slightly different application. 

Conclusions:

The development of super ports at distant and at offshore locations has created a need to simultaneously move multiple barges across ocean. That need provides scope to undertake research into an oceanic tug-barge technology capable of simultaneously moving multiple barges through ocean sailing conditions. The research may lead to the development of a twin-hull catamaran tug technology designed to couple to and navigate multiple parallel barges across ocean, at competitive operating costs. Such a concept would require considerable research and testing in the areas of tug-barge dynamics, in the area of structural engineering and would include tripod-triple-hull and quad-hull variants.

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Harry Valentine frequently contributes to Maritime Executive. He can be reached at [email protected] for comments and questions.