The systems are similar in basic principle, comprising a 360° all around towing system offering safety, controllability and, above all, flexibility to the performance of tugs, enabling them to rotate in all directions in a safe and controlled manner irrespective of the heading of the assisted vessel. Full power can be used in any direction and the line pull available can be enhanced considerably using indirect towing methods.

The Carousel towing system utilises a circular rail around the tug’s superstructure that supports a free moving carriage incorporating a towing winch that allows the towline to be deployed and remain connected regardless of the tug’s heading.

Two purpose built Carousel equipped 80 tons bollard pull tugs are under construction in Malaysia and due for completion within the next few months.

Mampaey has taken a different approach and use an ‘oval’ track having a natural bias when towing over the bow or stern and thus offering rather different handling characteristics. The first system has been fitted to a 13m tug/workboat designed by Macduff Ship Design and built for Peterhead Port Authority. Named Ugie Runner, the vessel was launched by MacDuff Shipbuilders on 19 April in readiness for extensive trials in May.

With trials completed and the vessel operational, the tug will travel south in June to demonstrate the DOT system at Seawork. A full report on this new vessel and towing system will appear in Maritime Journal in due course.

MacDuff Ship Design Ltd, which is gaining an increasing share in the workboat market, has reported an order from Pacific Ocean Engineering and Trading in Singapore to provide a design package for three new 22m twin screw harbour tugs. No final decision has been reached but the DOT system is also under consideration for those vessels.