Increasing Durability Performance of Lifeboat Launch Slipway Panels
Journal: Journal of Naval Architecture and Marine Engineering
The RNLI provides search and rescue cover around the coast of the UK and Ireland using various lifeboats and launch techniques. In locations where there is no natural harbour it is necessary to launch lifeboats with the aid of an inclined slipway. In these instances the lifeboat is held in a boathouse at the top of the slipway and released to slide into the water under its own weight, the lifeboat is later recovered to the top of the slipway using a winch line. RNLI slipway stations typically consist of an upper section of steel rollers followed by a plane, low friction composite lined lower section at a typical gradient of 1 in 5. Currently most slipway stations operate the ‘Tyne’ class lifeboat, this boat has been superseded by the new ‘Tamar’ class lifeboat which is being phased into service. The larger ‘Tamar’ lifeboat has required the upgrade and replacement of current slipways and boathouses as seen at Tenby and Padstow, the first slipway stations to receive the new lifeboat. These slipway stations have reported issues with high wear and friction along the slipway using the ‘Tamar’, particularly on the composite lined plane sliding section. This has prompted research into the friction and wear of the composite under varying lubrication and contact conditions using tribometers. The results of these tests were seen to be insufficient to explain the high wear and friction recorded at Tenby and Padstow and following detailed panel surveys at these locations a series of finite element simulations in conjunction with tribometer data were used to show that panel geometry and misalignments along the slipway form an important aspect of the overall slipway performance. Consequently a modified panel geometry is developed to reduce the effects of misalignments on friction and wear performance to ensure reliable slipway operation.