21st Century Propulsion: Partnering with the best for world-class results

When REINTJES, the German gearbox specialist, set about designing their reliable pod-drive propulsion system FORTJES® for the latest Dominator Ilumen yacht, the interested parties were introduced to CJR Propulsion and a successful collaboration was born.

Dominator had worked with REINTJES on its most recent D800 and both businesses were aware of CJR’s extensive experience in advanced fluid dynamics modelling. Following successful discussions at the METS Trade Exhibition, CJR was brought in to assist REINTJES in maximising performance efficiency and reducing vibration and cavitation even more. Therefore, REINTJES later selected CJRs propellers to be combined with its pod-drive system FORTJES® for the D800 project.

The FORTJES® propulsion system was developed by REINTJES to cope with almost any operating requirement and to exceed the latest industry standards, with increased efficiency, lower emissions and maximum comfort in a compact and space-saving design. At the centre of this concept was the use of counter- rotating propellers (CRP). The developed CRP push/pull system can be used for any semi-displacement or planing yacht design (from 300 to 2,000 kW per pod) and results in significantly reduced propeller load, as well as less cavitation and noise, and more thrust at high speed.

During the project phase for the D800, careful attention was paid to ensure every possible operating condition and any potential issue got resolved before production commenced. It was at this stage that REINTJES began working with CJR, as Simon Lewis, Head of CFD and Propeller Design, explains:

“This was a challenging project and one that required the full breadth of our CFD (computational fluid dynamics) capabilities. As mentioned, FORTJES® utilises contra-rotating propellers that are separated by a ‘gondola’, so the propellers do not follow standard propeller models for either single propellers or contra- rotating propellers.

“To ensure we would get the most out of the system, we created a large number of unsteady CFD simulations in order to understand the optimal position – effectively ensuring that both the forward and aft propellers are designed to deliver optimised efficiency, while minimising noise and vibration. This really was a complex objective, as the in ow into the aft propeller is highly turbulent and unsteady due to already having passed through the forward propeller.

Through our simulations and analysis, we managed to overcome each of our issues and, working closely with the FORTJES® and Dominator teams, designed the highly efficient propellers and twisted rudders that are now in production.”

The FORTJES® propulsion system comes with a rigid design that allows for peak manoeuvrability at low speeds and high stability at high speeds, as well as removing the need for an inclined shaft, so 100% of the engine’s thrust is pushing the vessel forward. The pod-drive system is also available with CJR designed twister rudders, which minimise the premature cavitation and related vibration through a twisted profile that is perfectly aligned with the propeller ow angles along the entire span, reducing the suction pressure peak that can form on or near the leading edge of the rudder.

Following Dominator’s collaborative involvement in the FORTJES® project, the Austrian-Italian shipyard will take full advantage of this unique propulsion system, using this dynamic pod-drive on the latest 28m Ilumen brand yacht. Angela Pernsteiner, Dominator Ilumen Managing Partner, spoke recently to Superyacht Business magazine about REINTJES and the collaboration taking place with a number of leading equipment manufacturers:

“REINTJES contributed to develop the perfect propulsion system for the Dominator Ilumen High Performance Hull. Our engineers met several times and were in close contact with the REINTJES engineers. Furthermore, the English company, CJR Propulsion, was another important part of the team. They joined forces with Ilumen and REINTJES to develop the perfectly matching twisted rudders and counter-rotating propellers.”

“From the outset we used a rational design approach typical of big ship or military vessel design” Andrea Agrusta, Head of Engineering and Hydrodynamics for Dominator and Ilumen