Now restructured and with a new position within the parent Group, the marine division now resides in a smart new headquarters in the Voith industrial complex in Heidenheim.

Chief Executive Officer Dr Jens-Erk Bartels explained that under the recent restructuring his division now fits more comfortably as a subsidiary of Voith Turbo the specialist power transmission arm of the Voith Group.

In the very recent past the company has invested heavily in expertise and research in order to maintain their market share of the specialised marine propulsion sector. Although the Voith Schneider propulsion unit is recognised for its quality and excellent performance as an omni-directional propeller, the prime objective of Dr Bartels and his researchers at Heidenheim is the improvement of hydrodynamic performance and reductions in the purchase price.

Every feature of the Voith Schneider range of products has been subjected to close scrutiny.

Led by Dr Dirk Jurgens, Head of Research and Development, and using 'state of the art' computer software, a small team of graduates continue to investigate all aspects of the design, manufacture and application of both established and new propeller designs. Sophisticated Finite Element Analysis work is carried out on virtually all of the components in the complex cycloidal mechanism to identify stress levels and validate component design. Work is also carried out on hull designs to identify stress levels and investigate the effects of wave action and vibration.

Specialist engineers prepare designs for manufacture using three-dimensional Computer Aided Design packages capable of solving manufacturing problems in a fraction of the time taken by traditional methods.

A key factor in the services available at the Heidenheim facility is a test tank dedicated to research work on new propeller and hull designs. The tank is of the re-circulating type and it is there that many new and advanced tractor tug designs are put through their paces. Using scale models, propeller and hull performance is measured electronically and water-flow patterns monitored using injected inks. Many new vessel designs are validated in the test tank, with Voith engineers working closely with naval architects and project engineers employed by vessel operators. In addition to this well proven research technology considerable progress has been made with the new Computational Fluid Dynamics (CFD) tools.

A number of innovations introduced by Voith over the past couple of years have dramatically improved the performance of the Voith Schneider propeller, particularly in the towage field.

New propeller blade designs incorporating a completely new cross-sectional profile and the addition of endplates, has resulted in a more uniform distribution of lift over the length of the blade and a reduction in cavitation and noise. Voith claim an overall increase in bollard pull of nearly 6 per cent can be achieved by adopting the new blade design.

Extensive tank testing and full-scale bollard pull trials have confirmed that the new blade profile provides an increase in performance of some 4.3 per cent and the fitting of endplates a further 1.3 percent.

The introduction last year of the first new six-blade propeller in the New Zealand tug Ahuriri was something of a breakthrough.

This extremely compact tractor is only 23.80m in length overall, with a beam of 11.00m and draft of 5.00m. Two Wartsila 8L 36A main engines produce a total of 4800kW (6522bhp) at 1000 rev/minute to power a pair of Voith propulsion units designated 32R6/210-2. The propellers have a blade orbit of 3.2m and each blade is 2.1m in length. On trials Ahuriri produced a bollard pull of 65 tonnes at MCR and 68 tonnes on overload, and a free running speed of 13 knots. With this performance this vessel has been heralded the most compact and powerful Voith water tractor ever produced for harbour towage.

Another innovation, about to be incorporated in a new tractor tug for the first time is the Voith 'Turbo-fin'. The skeg or fin is a key component in the tractor tug concept. Major developments have been introduced by naval architects, in conjunction with Voith Schiffstechnik, to achieve enhanced 'lifting forces' to enable tugs to steer or reduce the speed of very large tankers in an emergency. When an escort tractor tug positions itself transversely on the towline, in the indirect mode of operation, the hydrodynamic forces derived from the hull and skeg generate steering forces approximately twice that of the tug's static bollard pull.

The new Voith 'Turbo Fin' is a direct result of research into the hydrodynamic cross-section and flow characteristics of the skeg.

An increase in steering forces of over 20 percent is claimed by fitting a rotating cylinder in the leading edge of the skeg (the leading edge when travelling 'skeg first') providing a much improved boundary layer flow and a resulting increase in 'lift'. The cylinder requires very little power and can be driven by a hydraulic or electric motor.

Direction of rotation is critical and must be adjusted to suit the tug's angle to the towline - to port or starboard. Voith offer the device as a convenient and relatively inexpensive means of improving the performance of new vessels and existing tractors where stability and other design factors allow.

Co-operation between Voith and clients has resulted in some spectacular improvements in vessel performance. None more so than the work carried out in-conjunction with Norwegian tug owners Bukser Bergning AS which has developed a series of highly sophisticated 'fin-first' tractor tugs to carry out high-speed escort towing and berthing duties at Norwegian oil and gas terminals. The latest vessel, currently under construction, will incorporate further innovations including new six blade propellers with a 3.6m blade orbit and hydrodynamic improvements.

The propulsion units for the new Bukser escort tug were being manufactured in the Voith factory during the Maritime Journal visit. Each of the six blades is a high-quality steel forging weighing some 2 tonnes and machined to exacting tolerances inhouse. In order to reduce the inertia created by the rotation of six heavy blades and a massive hub, steps have been taken to reduce the weight of each blade by introducing a number of longitudinal holes.

The hub and rotor housings for these new propellers are massive and great care is taken during the assembly. Changes in blade pitch are created and controlled by a system of levers within the rotor hub known as the kinematics.

The introduction of a sixth blade has resulted in a particularly complex mechanism which when seen on the workshop bench is almost a 'work of art'.

Once assembly is completed the units are subjected to test running in a special facility in the factory before delivery to the shipyard.

Production at the Voith factory is running at about its normal level with propulsion units being completed for tugs and ferries around the world. There is also steady military workload. A number of navies employ Voith Schneider propulsion in mine hunters and other specialised craft resulting in the production of new units and a reconditioning service for others to a 'military' standard.