ORIGINAL ARTICLE An insight into the slamming behaviour of large high-speed catamarans through full-scale measurements Gunnar Jacobi • Giles Thomas • Michael R. Davis • Gary Davidson Received: 5 September 2012 / Accepted: 5 July 2013 / Published online: 24 July 2013 Ó JASNAOE 2013 Abstract The slamming behaviour of a large high-speed catamaran has been investigated through the analysis of full-scale trials data. The US Navy conducted the trials in the North Sea and North Atlantic region on a 98 m wave piercer catamaran, HSV-2 Swift, designed by Revolution Design Pty Ltd and built by Incat Tasmania. For varying wave headings, vessel speeds and sea states the data records were interrogated to identify slam events. An automatic slam identification algorithm was developed, considering the measured rate of change of stress in the ship’s structure coupled with the vessel’s pitch motion. This has allowed the slam occurrence rates to be found for a range of conditions and the influence of vessel speed, wave environment and heading to be determined. The slam events have been further characterised by assessing the relative vertical velocity at impact between the vessel and the wave. Since the ship was equipped with a ride control system, its influence on the slam occurrence rates has also been assessed. Keywords Slamming  High-speed catamaran  Full-scale measurements  Ride control system  Ship motions 1 Introduction Large high-speed catamarans are currently used for both commercial and military operations. They have seen a rapid development over the last 20 years, with the largest craft built in 1992 being 73 m [1], whilst in 2012, Incat Tasmania produced vessels of 112 m in length and Austal Ships in Western Australia delivered a catamaran ferry of 113 m. These vessels are designed with an emphasis on minimising structural weight to enable the ratio of dead- weight to lightship to be maximised, and thus to achieve a high vessel speed, whilst maintaining structural integrity in severe ocean environments. In the past, this conflict of requirements has led to problems, and several large high- speed catamarans are known to have suffered damage in extreme sea conditions, although details on such incidents are usually difficult to obtain due to the desire of ship- builders and operators to minimise publicity of such events; exceptions include Rothe et al. [2] and Thomas et al. [3]. Therefore, it is crucial that designers are provided with accurate wave loading information to determine appropriate design load cases for structural analyses in the design process. The wave loads experienced by large high-speed ca- tamarans can be split into two main categories: global wave loads and impact loads. Previous work has shown [3] that it is the impact loads, such as slamming, that dominate the creation of large bending moments in the vessels when operating in waves. After a slam event, the vessel may experience whipping as the natural modes of the structure are excited; in particular, the first longitudinal mode of vibration [4]. This whipping may make a significant con- tribution to reducing the fatigue life of a vessel [5]. For conventional slow-speed monohulls, classification societies have used an empirical approach based on G. Jacobi is a visiting researcher from University of Rostock, Germany. G. Jacobi  G. Thomas (&) Australian Maritime College, University of Tasmania, Locked Bag 1395, Launceston, TAS 7250, Australia e-mail: giles@amc.edu.au M. R. Davis University of Tasmania, Hobart, TAS, Australia G. Davidson Revolution Design Pty Ltd, Derwent Park, TAS, Australia 123 J Mar Sci Technol (2014) 19:15–32 DOI 10.1007/s00773-013-0229-y