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.