Alternative Lifeboat Slipway Bearing Materials Ben Thomas Bournemouth University Thomasb@Bournemouth.ac.uk

Typical Slipway - Padstow Padstow has recently received a new boathouse in order to accommodate the new Tamar class slip-launched lifeboat The slipway layout is typical of the next generation boathouses and slipways being built for the Tamar The slipway consists of an upper section of steel rollers and a lower section lined with low-friction 19mm thick jute/graphite infused phenolic resin composite panels 19mm jute/phenolic composite panels Steel rollers

Lifeboat Slipway Launch

Lifeboat Slipway Recovery - Alignment ropes - Winch cable Lifeboat alignment and attachment of winch cable – alignment ropes and winch cable indicated

Lifeboat Slipway Recovery - Quarter stop ropes - Winch cable Fig. 3.1.2i: Haul Stage – Rope quarter stops and winch cable keel attachment position shown

Slipway Lifeboats

Slip-launched Lifeboats Tamar Class Lifeboat The Tamar slip-launched lifeboat is designed as a replacement to the Tyne class lifeboat. It is significantly larger and heavier than the Tyne and this has meant new slipways and boathouses have had to be built to accommodate it. The Tamar currently operates from new boathouses and slipways at Tenby, Padstow and Cromer Slip-launched Lifeboats Tyne Tamar Year Introduced 1982 2006 Length 14.3m  16m Beam 4.48m  5m Draught 1.26m  1.35m Speed 17.6 knots 25 knots Displacement 26 - 27 tonnes  ~ 35 tonnes Construction Steel  FRP Range 240n. miles  250n. miles Crew 7  6

Slipway Lining Materials Weather Treated Wood – Traditional c.1850 Nickel/Chromium carbide coated Steel – c.1980 Jute/Graphite Infused Phenolic Resin Composite – c.1996

Introduction & Previous Work Research is a continuation of work carried out at Bournemouth university to investigate the suitability of the jute/graphite infused phenolic resin composite as a slipway bearing material for use with the new Tamar class lifeboat Previous testing used tribometers in conjunction with finite element models and surface analysis to develop an understanding of the friction and wear mechanisms along the slipway The results of the previous work show that the jute/graphite composite is only marginally suited for use as a slipway lining with the new Tamar lifeboat, with higher that expected friction and wear found This work looks at the suitability of an alternative, nylon/phenolic resin composite for slipway lining use

Introduction & Previous Work

Slipway analysis Launch Scenario It follows that:- µ max < 0.2 for a 1 in 5 slipway µ max < 0.167 for a 1 in 6 slipway

Slipway analysis Recovery Scenario The recovery winch is specified for a pull capacity of 12 tonnes, this means that the maximum friction coefficient during recovery that will meet this requirement on a standard 1 in 5 slipway is: µ max < 0.150 for a 1 in 5 slipway µ max < 0.181 for a 1 in 6 slipway Increasing the winch capacity to 13.7 tonnes in the case of the 1 in 5 slipway will allow the overall friction specification to meet the launch specification at µ max < 0.2

Nylon/phenolic composite vs Nylon/phenolic composite vs. Jute/graphite phenolic composite: Material Properties

Nylon/phenolic composite vs Nylon/phenolic composite vs. Jute/graphite phenolic composite: Material Properties

Nylon/phenolic composite vs Nylon/phenolic composite vs. Jute/graphite phenolic composite: Material Properties

Lubricants Outline Unlubricated Dry sliding is the simplest way to operate, providing low enough friction and frictional heating can be achieved Grease Grease lubrication involves the manual application of grease to the slipway before each launch and recovery – this is subsequently washed in to the sea around the base of the slipway where it has the potential to bioaccumulate Biogrease Biogreases are investigated as a direct substitute for traditional greases with their ability to biodegrade mitigating the bioaccumulation potential Water Lubrication Water lubrication involves using jets of water mounted at the top of the slipway to run water down the keelway

Test Machines: TE57

Tests schedule Lubricant CONTACT FORCE TESTS Contact Force (N) Dry Freshwater Seawater Marine Grease Biogrease #1 #2 #3 5 C1 C11 C21 C31 C41 C51 C61 10 C2 C12 C22 C32 C42 C52 C62 15 C3 C13 C23 C33 C43 C53 C63 20 C4 C14 C24 C34 C44 C54 C64 25 C5 C15 C25 C35 C45 C55 C65 30 C6 C16 C26 C36 C46 C56 C66 35 C7 C17 C27 C37 C47 C57 C67 40 C8 C18 C28 C38 C48 C58 C68 45 C9 C19 C29 C39 C49 C59 C69 50 C10 C20 C30 C40 C50 C60 C70

Combined Results: Friction Coefficient

Combined Results: Mean Friction Coefficient

Nylon/phenolic composite vs Nylon/phenolic composite vs. Jute/graphite phenolic composite: Friction Comparison

Conclusions The new nylon/phenolic composite is shown to meet the friction criteria for all lubricants and at all contact pressures tested The dry sliding friction is lower than the friction specification which will reduce stick-slip behaviour on the slipway if the lubrication regime breaks down locally Wear rates are shown to be even and low at all contact pressures tested The reduced operating temperature of the nylon/phenolic composite compared to the original jute/phenolic composite is likely to increase the chances of reaching the P-V limit at launch if run unlubricated

Recommendations The new nylon/phenolic composite can be recommended for use on RNLI slipways providing suitable lubrication is provided for cooling to prevent PV limit effects at launch Water lubrication is shown to be as effective as grease lubrication in reducing friction on the composite and can also be recommended over grease lubrication on cost, environmental and safety grounds Panel misalignments also play a role in the friction along the slipway and should be reduced to below ~2mm Fitting a chamfer to slipway panels may help to reduce friction concentrations