Posts By / Julie Northam

Dr Ben Thomas and Prof Mark Hadfield – RNLI slipways

Lifeboat being launched (c) RNLI Nicholas LeachDr Ben Thomas and Prof Mark Hadfield (DEC) have been undertaking some marvellous research with the RNLI. The research was shortlisted for the 2010 Times Higher Education (THE) Award for Outstanding Contribution to Innovation & Technology, and you can read all about what they’ve achieved here on the blog!

Ben Thomas, RNLI researchThe Royal National Lifeboat Institution (RNLI) is a charitable organisation that provides marine search and rescue cover along the entire coast range of the UK and Ireland. Lifeboat slipway stations are an essential part of the RNLI’s coastal protection; they allow lifeboat stations to be located in areas where there is no natural harbour and for lifeboats to be launched in almost any weather conditions. However, as the size and mass of lifeboats have increased over the years the traditional wood or steel lined slipways have been shown to be insufficient, with problems of friction and wear affecting the reliability of slipway launches. New composite slipway panels have reduced these issues but high friction and wear problems remain, with replacement costs for the expensive composite panels placing strain on the RNLI’s scarce resources.

Traditionally friction is reduced by manually applying grease to the slipway, but this practice has safety implications for the crew and has raised environmental concerns regarding the repeated release of grease into the sea at the base of the slipway.

Analysing the contact conditions between the 15cm wide keel of a 35 tonne lifeboat and the slipway lining presented considerable technical challenges, particularly as the lifeboat approaches speeds of 45kph during launch, and this required the development of a new multi-disciplinary approach using aspects of tribology, finite element analysis, life cycle analysis and real world data collection, with experimental results combined with real slipway experience and computer simulations to develop  a deeper understanding of the nature of the friction and wear problems on the slipway.

The data collected indicated that the reliability of lifeboat slipways could be greatly increased by ensuring the slipway panels were well aligned along the length of the slipway, it also showed that a small change to the panel geometry to incorporate a chamfer significantly reduced wear development and the adverse effects of panel misalignments on launch and recovery friction.

The project showed that it was feasible to substitute the currently used marine grease lubrication with biodegradeable greases, reducing the effects of grease bioaccumulation at the base of the slipway. The research also proposed the use of a novel water lubrication system instead of grease directly applied to the slipway, with the potential to greatly reduce both the operational costs and the environmental impact of slipway launches. These water lubricated systems have subsequently begun to be adopted across the RNLI slipway network.

The research recommendations will be used by the RNLI to improve the lifeboat slipways in the UK and Ireland. This will increase the reliability of slipway launches and recoveries and reduce the risk exposure of the volunteer lifeboat crew. The improvements will also reduce the operating costs of the RNLI.

The changes recommended by the research are already underway, the new slipway lining material has been fitted to the newer slipway stations (e.g. Tenby, Padstow etc.) already and the water lubrication systems are also in place. The recommended slipway lining material and water lubrication systems are being phased in across the remaining UK slipway station network over the next few years, coinciding with the simultaneous rollout of the new Tamar lifeboat to the slipway stations.

The combined effects of Prof Hadfield and Dr Thomas’s research recommendations will allow the RNLI to save up to £200,000 per year in operational costs once these are adopted across the slipway station network. The changes will also increase the reliability of lifeboat slipway launches and recoveries, reducing the risk exposure of the volunteer lifeboat crew who crew each slipway station, and allowing the continued safe operation of the RNLI’s crucial role in preserving life along the coast of the UK and Ireland. The final benefit is showing that the previous lubrication system involving the manual application of grease to the slipway by lifeboat crewmen can be replaced by an automatic water based system, thus reducing the cost and environmental impact of lifeboat slipway launches as well as the risks lifeboat crew members are exposed to on the slipway.

Dr Ben Thomas undertook the research, supervised by Prof Hadfield, as part of a CASE award studentship funded by the EPSRC and the RNLI. In addition, the RNLI commissioned Prof Hadfield and Dr. Thomas to undertake additional research into alternative slipway materials in 2009.

Further details:

RNLI webpage: Lifeboat project ready for awards splash

BBC Cornwall news story: RNLI slipway research

AlphaGailieo webpage: RNLI lifeboat launch benefits from BU research