Abstract

The Royal National Lifeboat Institution provides a marine search and rescue service using a variety of lifeboats and lifeboat stations. In locations where there is no natural harbour it is necessary to use an inclined slipway to launch the lifeboat into the sea. Lifeboat slipway stations consist of an initial section where the boat is held on rollers followed by an inclined keelway lined with low friction composite materials, the lifeboat is released from the top of the slipway and proceeds under its own weight into the water. Currently, a graphite infused jute/phenolic resin composite is the preferred slipway lining material for all lifeboat launch slipways, chosen for its potential ability to run unlubricated or with simple water lubrication, without the manually applied grease previously used on steel lined slipways. However research conducted at Bournemouth University [1-4] indicates that this may not be the most suitable material available due to a relatively high dry sliding friction coefficient and the ineffectiveness of graphite in reducing friction and wear under lubricated conditions. Following this research it was proposed to investigate another similar potential slipway lining material in a similar fashion. The new composite material is tested using reciprocating tribometers and directly compared with the previously tested composite material. Results show that the new composite material performs significantly better that the existing slipway lining, meeting the required friction coefficient specification using all lubricants tested. This leads to the recommendation to continue with the adoption of the new composite as a slipway bearing material, and that this material should be run using water lubrication. Water is selected as the preferred lubrication system due to its ability to reduce sliding friction far below the specification even for shallower 1 in 6 slipways, and also for its cooling effect during the high speeds and high frictional heating in the contact area towards the base of the slipway likely during lifeboat launches.

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