RS & WBV Whole Body Vibration Workshop Review
Workshop lead John Haynes opened the day saying that, ‘A shock mitigation strategy is essential for all craft that undertake open sea transits or operate in rough water.
He added, 'Recent focus has been on developing mechanical suspension seats to reduce effects of vertical accelerations. Fore-aft, lateral and vector forces now require attention, plus seat cushion performance and comfort need improving.’
Over 80 maritime professionals attended two unique one day events focused on the sub IMO / sub 80 feet sector in Southampton UK this April. The fast moving and dynamic RS & WBV (Repetitive Shock & Whole Body Vibration) Workshop brought together an international group of experts armed with the latest knowledge to identify problems that affect the maritime sector worldwide.
The definition of shock mitigation is to make a violent collision or impact less intense. The presentation by John Haynes - Managing Director of Shock Mitigation highlighted that a challenge for the builders of next generation RHIBs and high speed craft is delivering platforms that balance high performance with the physical demands on crew and passengers. With the arrival of unbreakable boats plus a surplus of engine power feedback from the human body is crucial input that designers and naval architects must consider for the next generation of fast boats. Dr Tom Gunston of the ISO Standards Seat Testing Working Group explained how laboratory testing and understanding the metrics related to repetitive shock and whole body vibration can reduce the incidence of injury. The objective of this session was to bring together a body of information that end-user organisations and industry can utilize to develop a holistic approach to shock mitigation on fast boats.
The next session was presented by Hans van der Molen - Head of Technical Projects and Innovation for KNRM the Royal Netherlands Lifeboat service. He explained why their vessels are being designed to the most rigorous standards, ‘As KNRM rescue vessels have to be deployable in all weather conditions seakeeping and stability are the most crucial factors in safety. For the crew however, comfort and user-friendliness are also key features.’
He showed the innovative 19 metre (62 feet) rescue vessel named ‘NH1816’ built by Damen Shipyards Group in collaboration with the Maritime Technology faculty at Delft University and De Vries Lentsch Naval Architects. This vessel combines all of the technical, ergonomic and operational features the KNRM wanted in a remarkable new design. The new rescue vessel is intended to be the replacement for the current 19 metre Arie Visser-class vessels. Specific requirements to be met by the new fleet, compared to Arie Visser Class, include significant reduction of vertical and horizontal accelerations. Designers are aiming for a minimum of 40% reduction in G-forces and significant noise reduction, set at maximum 75Db. Besides reduction of vibrations, design focus is on ergonomically sound wheelhouse design including wheelhouse climate control and other increased crew comfort items.
At this point it was highly relevant to hear from Professor Jelte Bos of TNO the Dutch Organisation for Applied Scientific Research. He highlighted that while high speed craft technology develops continuously, resulting in increasing vessel capabilities, human evolution stays far behind. As a result, the performance of the system as a whole is determined more and more often by the human factor. Technological developments have also resulted in a shift of interest with respect to human health, comfort and performance from whole body vibration to repeated shocks. The increasing impact of these shocks is largely determined by the forces exerted by the slamming boat through the seat to the vertebra. A health risk is then not only caused by single impacts crushing vertebra and intervertebral discs, but also by repeated shocks over longer periods of time, up to years. Accumulation of minor and recoverable injuries, may then finally result in irreversible injury.
Professor Bos added, ‘The effects of single impacts can be analysed and predicted fairly well using biomechanical models taken from the automotive sector. These analyses can help in setting better health criteria, as well as to design better suspension seats. However the long-term effects of repeated shocks are obscured by a lack of knowledge. Because these effects often remain under the skin until it is too late, a major challenge therefore concerns the charting of the dose-effect relationship. This will however require a shift of focus and interest from hydromechanical issues to human medical factors.’
Dr Thomas Coe is a Senior Consultant with Frazer-Nash Consultancy currently on secondment to the Naval Design Partnership as the High Speed Craft Group Manager and Technical Lead of the UK Ministry of Defence Maritime (MoD) Whole Body Vibration Project. This project focuses on the so called DLOD (Defence Lines of Development) approach which maps well on to the EU / UK control of vibration at work regulations. This DLOD approach has helped the MoD to focus on the multiple facets of managing the issue of protecting people from harm. This includes risk assessment, health monitoring and targeted training.
The presentation showed the RS and MWBV (Repetitive Shock and Maritime Whole Body Vibration) Conditioning Programme developed by the Royal Navy. The exercise programme brings together a series of exercises to assist crews and passengers to prepare themselves for transits on fast craft. The objective being to reduce fatigue and injury. The RS and MWBV Conditioning Programme is developed from fundamental research by medics and physical training instructors in collaboration with the Maritime WBV project. The presentation also considered the wider MoD approach to health monitoring.
The day ended with a panel discussion featuring James Taylor - CEO of SKYDEX Technologies, Paul Taylor - CEO of SHOXS and Julian Morgan - Technical Director of KPM Marine The discussion focussed on ‘Learning from On Water Trials, Testing and Other Transport Sectors to Improve Crew Safety.’
Next Workshps in Southampton UK:
James Taylor showed what SKYDEX engineers have learned from developing cushion decking and shock mitigating seat cushions for various transport sectors. Metrics demonstrate how foam cushions can be replaced with innovative SKYDEX cushions, utilizing proprietary polymer structures, to reduce the effects of RS and WBV. For the marine sector this improved protection can be achieved with no weight gain and within the existing seat footprint on jockey seating for RHIBs, on conventional wheelhouse seating and to further improve the performance of suspension seating.
Paul Taylor looked at the issue of sightlines and the lessons that SHOXS have learned from developing high performance suspension seating solutions for military organisations both sides of the Atlantic. When working with large groups of people it is important to develop seating to accommodate all body sizes. He showed significant differences between the sightlines of a 5th percentile person compared to a 95th percentile person. He highlighted that a solution to improving sightlines is raising occupants off the deck using footrests.
Julian Morgan gave an insight into lessons learned by KPM from gathering big data as part of seat versus hull classification. As a collaborative design and manufacturing company they focus on seat design criteria including the human interface, whole body vibration and crash testing plus legal issues and regulations. He showed data that KPM have gathered from wind farm support vessels. The data has enabled them to develop suspension seat classification for matching seat performance to vessel performance.
Workshop topics focussed on visible issues today, plus hidden areas of concern that the professional maritime sector may need to face tomorrow. John Haynes summed up the day, ‘We asked the audience for burning questions – and we certainly got them with plenty of constructive discussions. The RS & WBV Workshop clearly showed that as boats become faster and tasks more challenging, human factors are a growing concern for professional organisations worldwide.’
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