Integrated design of hull form and structure for composite double-stepped deep-V high-speed craft

Objectives To meet the integrated requirements of high speed, seakeeping performance, and slamming resistance for composite high-speed craft operating in complex nearshore swell conditions, an integrated design and experimental verification study is carried out for a double-stepped deep-V hull form and a slamming-resistant composite hull structure.

Methods Based on a predetermined large-deadrise double-stepped deep-V hull configuration, comparative model resistance tests are carried out to investigate its hydrodynamic performance at different speed regimes. A region-specific composite hull structure consisting of carbon-fiber-reinforced marine epoxy laminates and PVC foam sandwich panels is designed. The design bottom slamming pressures are determined in accordance with relevant China Classification Society (CCS) rules, and a full-ship finite element model is established in Abaqus to evaluate the overall deformation, principal stress distributions, and material failure margins under equivalent static design loads. Full-scale trials, including fully loaded high-speed operation and sustained high-speed operation, are subsequently conducted to assess the engineering applicability of the proposed hull-form and structural design.

Results Model tests showed that the drag reduction achieved by the double-stepped configuration was primarily concentrated in the high-speed planing regime. At the maximum design speed, the effective power of the double-stepped deep-V hull was approximately 11.5% lower than that of the baseline deep-V hull. The calculated maximum design pressure on the hull bottom was 61.95 kPa. Finite element analysis showed that all major stress components remained below the corresponding material strength limits, and the maximum failure index was less than 1. High-stress regions were mainly concentrated in the longitudinal bottom stiffeners, beam–shell connections, and local geometric transitions. Full-scale trials of the vessel built to this design under fully loaded conditions showed that, with a payload of 7.5 t, the maximum downstream and upstream speeds were 47 kn and 44 kn, respectively, yielding a two-way average speed of 45.5 kn. At 100% main engine load and 2,400 r/min, the vessel maintained a speed of approximately 45.2 kn for 120 min of continuous operation. All performance indicators met the design requirements.

Conclusions The proposed double-stepped deep-V hull can effectively improve the hydrodynamic performance in the high-speed planing stage, while the carbon-fiber laminate/PVC foam sandwich structure meets the requirements of lightweight and slamming-resistant design. The integrated "hull form-structure-test" methodology can provide a reference for the engineering design and performance verification of composite high-speed craft.