The DOT system comprises a new oval shaped radial support towline attachment that can be combined with a wide range of propulsion systems and hull shapes in order to improve towing performance. Unlike the completely circular 'Carrousel' system, the oval shape is said to offer additional flexibility in design requirements, allowing the width, length and specific curvature to be chosen to meet the owner's special needs. This flexibility also offers advantages not only for new tugs but also for retrofitting on existing tugs.

The DOT system allows a large area inside the oval shape with sufficient space for adequate accommodation, machinery, exhaust uptakes, vents, cranes and workboats.

An oval support rail allows the towing connection to move easily between the towing points for working ahead and astern without restriction. The shape of the oval rail automatically positions the towing point forward when sailing astern and aft when sailing ahead. A close match of towline forces above the water and the hydrodynamic forces below enables an optimal manoeuvring performance under full control during towing operations, even at high speeds.

Towing can take place at will, over bow or stern and the radial support of the towline attachment point minimises the capsizing moment and prevents capsizing due to towline forces.

A DOT installation comprises a heavy deck mounted rail that is an integral part of the ship's structure and the DOT system connects a Mampaey towing hook to the rail. Towing forces are equally distributed on the rail by means of a spreader bar, two carriages and a series of rollers. Finite Element Calculations have been used to validate the design of the structure and the interface between the rail and the vessel. Development of the system has been in the hands of Dr Markus van der Laan, inventor of the original Carrousel system, working closely with Mr Gerard Mampaey.

The DOT system can be integrated in various designs and a typical example suggests a small harbour tug of 20m length and 25 ton BP. In this oval shaped accommodation arrangement safe access on deck is achieved in combination with daytime accommodation space below. Mampaey are adamant that the DOT system has been tested thoroughly and 'is ready to go'.

During testing the DOT system was subjected to a number of trials mounted on a 4.8m, manned scale model tug that proved highly successful. This was followed by mounting the first full sized DOT system on the deck of a pontoon barge and applying a 200% working load of 60 tons. Excellent results from this test demonstrated that the design requirements were met successfully and initiated the official start of the delivery of the 30 ton SWL DOT system equipped with a tow hook.

Larger sized systems and a towing winch are currently under development.