Testing Methodology for Seat Suspension Units in High-Speed Planing Craft

High-speed planing craft, such as rigid hull inflatable boats (RHIBs), are frequently subjected to severe hydrodynamic impacts during operation, particularly in rough sea conditions. These impacts pose significant risks to the comfort, health, and performance of the crew. Resilient seat suspension units (SSUs) are designed to mitigate these impacts, but their effectiveness is challenging to assess under real-world conditions due to the potential hazards to the crew and variability of sea trials. This paper outlines a methodology for replicating the effects of slamming events experienced by high-speed craft in a controlled environment. By using drop tests of a pontoon and characterising the dynamic environment with the Shock Response Spectrum (SRS), this study enables standardised testing of SSUs without the need for repeated live sea trials to evaluate and compare different seat designs. INTRODUCTION High-speed planing craft, particularly rigid hull inflatable boats (RHIBs), are widely used in commercial, military, and leisure sectors due to their ability to achieve high speeds. However, these vessels frequently experience significant hydrodynamic impacts, even in moderate sea states. Such impacts can cause discomfort, fatigue, and potential injury to crew members, making mitigation critical. To address this, many RHIBs are equipped with resilient seats incorporating spring-damper mechanisms designed to absorb and dampen impact forces, as illustrated in Fig. 1. Extensive research has been conducted to evaluate the performance of suspension seat units (SSUs), including laboratory-based drop-testing methods developed in the US and Canada. For example, studies by (Riley 2018), (Marshall 2020) and (AuCoin 2014), use surrogate media such as wedges into sand or honeycomb structures to simulate impact events. These methods have provided valuable insights into seat dynamics under controlled, repeatable conditions. A widely used approach in these studies is the Shock Input Method, which characterises wave impact severity using four parameters: acceleration pulse shape, peak amplitude, pulse duration, and rate of application. This framework allows for systematic analysis and has been effective in many contexts. However, challenges can arise when estimating these timedomain parameters, particularly pulse duration, under complex, irregular slamming conditions typical of high-speed craft.