Alternative Lifeboat Slipway Alternative Lifeboat Slipway Bearing MaterialsBearing Materials

Ben ThomasBournemouth University

Thomasb@Bournemouth.ac.uk

Typical Slipway - Typical Slipway - PadstowPadstow

19mm jute/phenolic composite panels

Steel rollers

Padstow has recently received a Padstow has recently received a new boathouse in order to new boathouse in order to accommodate the new Tamar accommodate the new Tamar class slip-launched lifeboatclass slip-launched lifeboat

The slipway layout is typical of The slipway layout is typical of the next generation boathouses the next generation boathouses and slipways being built for the and slipways being built for the TamarTamar

The slipway consists of an upper The slipway consists of an upper section of steel rollers and a section of steel rollers and a lower section lined with low-lower section lined with low-friction 19mm thick jute/graphite friction 19mm thick jute/graphite infused phenolic resin composite infused phenolic resin composite panelspanels

Lifeboat Slipway LaunchLifeboat Slipway Launch

- Alignment ropes - Winch cableLifeboat alignment and attachment of winch cable – alignment ropes and winch cable indicated

Lifeboat Slipway RecoveryLifeboat Slipway Recovery

Lifeboat Slipway RecoveryLifeboat Slipway Recovery

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

Slipway LifeboatsSlipway Lifeboats

Oakley Class:12.5t11m

Tyne Class:26t

14m

Tamar Class:31.5t16m

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Tamar Class LifeboatTamar Class Lifeboat The Tamar slip-launched lifeboat is designed as a The Tamar slip-launched lifeboat is designed as a

replacement to the Tyne class lifeboat. It is significantly replacement to the Tyne class lifeboat. It is significantly larger and heavier than the Tyne and this has meant new larger and heavier than the Tyne and this has meant new slipways and boathouses have had to be built to slipways and boathouses have had to be built to accommodate it.accommodate it.

The Tamar currently operates from new boathouses and The Tamar currently operates from new boathouses and slipways at Tenby, Padstow and Cromerslipways 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 MaterialsSlipway Lining Materials

Weather Treated Weather Treated Wood – Traditional Wood – Traditional c.1850c.1850

Nickel/Chromium Nickel/Chromium carbide coated Steel carbide coated Steel – c.1980– c.1980

Jute/Graphite Infused Jute/Graphite Infused Phenolic Resin Phenolic Resin Composite – c.1996 Composite – c.1996

Introduction & Previous Introduction & Previous WorkWork

Research is a continuation of work carried out at Research is a continuation of work carried out at Bournemouth university to investigate the suitability Bournemouth university to investigate the suitability of the jute/graphite infused phenolic resin composite of the jute/graphite infused phenolic resin composite as a slipway bearing material for use with the new as a slipway bearing material for use with the new Tamar class lifeboatTamar class lifeboat

Previous testing used tribometers in conjunction with Previous testing used tribometers in conjunction with finite element models and surface analysis to develop finite element models and surface analysis to develop an understanding of the friction and wear an understanding of the friction and wear mechanisms along the slipwaymechanisms along the slipway

The results of the previous work show that the The results of the previous work show that the jute/graphite composite is only marginally suited for jute/graphite composite is only marginally suited for use as a slipway lining with the new Tamar lifeboat, use as a slipway lining with the new Tamar lifeboat, with higher that expected friction and wear foundwith higher that expected friction and wear found

This work looks at the suitability of an alternative, This work looks at the suitability of an alternative, nylon/phenolic resin composite for slipway lining usenylon/phenolic resin composite for slipway lining use

Introduction & Previous Introduction & Previous WorkWork

Slipway analysisSlipway analysis

Launch ScenarioLaunch Scenario

It follows that:- It follows that:- µ max < 0.2 for a 1 in 5 slipwayµ max < 0.2 for a 1 in 5 slipway µ max < 0.167 for a 1 in 6 slipwayµ max < 0.167 for a 1 in 6 slipway

Slipway analysisSlipway analysisRecovery ScenarioRecovery Scenario

The recovery winch is specified for a pull The recovery winch is specified for a pull capacity of 12 tonnes, this means that the capacity of 12 tonnes, this means that the maximum friction coefficient during recovery maximum friction coefficient during recovery that will meet this requirement on a standard 1 that will meet this requirement on a standard 1 in 5 slipway is:in 5 slipway is:

µ max < 0.150 for a 1 in 5 slipwayµ max < 0.150 for a 1 in 5 slipway µ max < 0.181 for a 1 in 6 slipwayµ max < 0.181 for a 1 in 6 slipway Increasing the winch capacity to 13.7 tonnes in Increasing the winch capacity to 13.7 tonnes in

the case of the 1 in 5 slipway will allow the the case of the 1 in 5 slipway will allow the overall friction specification to meet the launch overall friction specification to meet the launch specification at specification at µ max < 0.2µ max < 0.2

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

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Nylon/phenolic composite Jute/graphite phenolic composite

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

Material PropertiesMaterial Properties

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

Material PropertiesMaterial Properties

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Lubricants OutlineLubricants Outline UnlubricatedUnlubricated

Dry sliding is the simplest way to operate, providing Dry sliding is the simplest way to operate, providing low enough friction and frictional heating can be low enough friction and frictional heating can be achievedachieved

GreaseGreaseGrease lubrication involves the manual application Grease lubrication involves the manual application of grease to the slipway before each launch and of grease to the slipway before each launch and recovery – this is subsequently washed in to the sea recovery – this is subsequently washed in to the sea around the base of the slipway where it has the around the base of the slipway where it has the potential to bioaccumulate potential to bioaccumulate

BiogreaseBiogreaseBiogreases are investigated as a direct substitute Biogreases are investigated as a direct substitute for traditional greases with their ability to for traditional greases with their ability to biodegrade mitigating the bioaccumulation potentialbiodegrade mitigating the bioaccumulation potential

Water LubricationWater Lubrication

Water lubrication involves using jets of Water lubrication involves using jets of water mounted at the top of the slipway to water mounted at the top of the slipway to run water down the keelwayrun water down the keelway

Test Machines: TE57Test Machines: TE57

Tests scheduleTests scheduleCONTACT FORCE TESTS

Contact Force

(N)

Lubricant

Dry Freshwater SeawaterMarine Grease

Biogrease #1

Biogrease #2

Biogrease #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 Combined Results: Friction CoefficientCoefficient

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Linear (1 in 5 Criteria)

Linear (1 in 6 Criteria)

Combined Results: Mean Friction Combined Results: Mean Friction CoefficientCoefficient

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Dry Freshw ater Seaw ater MarineGrease

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Biogrease#3

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

Friction ComparisonFriction Comparison

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Dry Freshwater Seawater MarineGrease

Biogrease#1

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Biogrease#3

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T11 F21 Linear (1 in 5) Linear (1 in 6)

ConclusionsConclusions The new nylon/phenolic composite is shown to meet The new nylon/phenolic composite is shown to meet

the friction criteria for all lubricants and at all the friction criteria for all lubricants and at all contact pressures testedcontact pressures tested

The dry sliding friction is lower than the friction The dry sliding friction is lower than the friction specification which will reduce stick-slip behaviour specification which will reduce stick-slip behaviour on the slipway if the lubrication regime breaks down on the slipway if the lubrication regime breaks down locallylocally

Wear rates are shown to be even and low at all Wear rates are shown to be even and low at all contact pressures testedcontact pressures tested

The reduced operating temperature of the The reduced operating temperature of the nylon/phenolic composite compared to the original nylon/phenolic composite compared to the original jute/phenolic composite is likely to increase the jute/phenolic composite is likely to increase the chances of reaching the P-V limit at launch if run chances of reaching the P-V limit at launch if run unlubricatedunlubricated

RecommendationsRecommendations The new nylon/phenolic composite can be The new nylon/phenolic composite can be

recommended for use on RNLI slipways recommended for use on RNLI slipways providing suitable lubrication is provided for providing suitable lubrication is provided for cooling to prevent PV limit effects at launchcooling to prevent PV limit effects at launch

Water lubrication is shown to be as effective as Water lubrication is shown to be as effective as grease lubrication in reducing friction on the grease lubrication in reducing friction on the composite and can also be recommended over composite and can also be recommended over grease lubrication on cost, environmental and grease lubrication on cost, environmental and safety groundssafety grounds

Panel misalignments also play a role in the Panel misalignments also play a role in the friction along the slipway and should be reduced friction along the slipway and should be reduced to below ~2mmto below ~2mm

Fitting a chamfer to slipway panels may help to Fitting a chamfer to slipway panels may help to reduce friction concentrationsreduce friction concentrations