A new lightweight sandwich composite concept may reduce the weight of a RoPax superstructure by as much as 60%. This opens up for increased loading capacity, and thus increased profits for operators.

With their long and successful track record in demanding and weight-critical applications, lightweight materials have until now been used for such things as high-speed light craft and naval ships. The benefits of these materials have so far not been available to the merchant ship designer as international regulations (SOLAS) have required that structures be made of non-combustible materials. However, a recent amendment to these regulations allows alternative arrangements provided that adequate safety is demonstrated by an engineering analysis.

DNV, together with Stena, FiReCo and Brodrene Aa, has found that the introduction of a lightweight composite superstructure module for a RoPax design case leads to a 60% decrease in weight for that module compared to a traditional steel design. This takes into account both structural fire protection and other risk control measures.

The benefits of the new technology have been explored by applying it to the design of one of Stena’s existing ships. Two years of operation will cover the slightly higher building costs. Stena is currently considering the new concept with great interest.

“This new concept is very interesting for us. Together with DNV we are currently exploring the benefits of this technology in a new project and discussing design approval with the appropriate national authorities,” says Harry Robertsson, technical director of Stena Rederi AB.

A comprehensive risk-based design process has been performed, in which the risks were estimated based on available fire statistics, fire simulations, fire test trials and evacuation simulations.

A broad range of risk control options was studied and the cost-effective ones were adopted. An acceptable level of safety was documented for the new risk-based design.

“Our results are very promising for more efficient and profitable merchant ship designs in the future,” says DNV’s CEO Henrik O. Madsen.

This is one of eight concepts being considered within the partially EU-funded SAFEDOR programme, responding to the needs of the EU maritime industry for innovative solutions for high quality, cleaner and safer transport. Stena, FiReCo, Brodrene Aa and DNV are the SAFEDOR programme partners carrying out this design concept, which was rated the best of all eight by an expert committee.