Integration of Inboard Propulsion in Shock Mitigating Membrane Hull Technology

Abstract

Membrane Hull Technology is a strength based marine vessel design concept that seeks to utilize the in-plane properties of fiber reinforced composites to generate a lighter weight vessel with inherent shock mitigation benefits. MHT has been applied on several Naval crafts yet the design features of inboard propulsion systems have not been addressed. Inboard propulsion systems are a very common form of propulsion used in many types of marine vessels especially larger vessels. This thesis seeks to overcome the inboard engine mounting challenges of MHT which limits use of this technology in the marine industry. The fundamental design elements of MHT were followed to ensure weight savings and the shock mitigation elements of MHT. An engine platform that is primarily keel supported with composite spring supports connecting to the largest deflection regions of the MHT structure was designed and analyzed. A model without engines was subjected to the same loading conditions to further analyze this mounting concept and allow direct comparisons. This enabled the ability to not only test the viability of this engine mounting technique in an MHT structure, but to also analyze the alteration of hull behavior due to the platform. Results show that this design concept effectively allows the direct mounting of engines to an MHT hull structure without the generation of hard points. Although a viable mounting option for inboard engines in an MHT structure, reductions in hull flexibility were observed in the aft section of the hull around the engines in a region with low slamming frequency. In the forward section of the vessel where most of the major slamming occurs minimal reductions in deflection were observed. This suggests that this mounting concept would not significantly alter the ride quality of the vessel in normal operating conditions. However, when comparing to a traditional hull, a significant improvement in structural performance in weight and shock mitigation was observed. The results of this thesis highlight the potential to take advantage of this type of structure and to overcome additional challenges with this type of marine structure.