1. Alternative Lifeboat Slipway Bearing Materials
Ben Thomas
Bournemouth University

2. 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

3. Lifeboat Slipway Launch

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

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

6. Slipway Lifeboats

7. 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
tonnes
 ~ 35 tonnes
Construction
Steel
 FRP
Range
240n. miles
 250n. miles
Crew 7  6

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

9. 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

10. Introduction & Previous Work

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

12. 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 < for a 1 in 5 slipway
µ max < 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

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

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

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

16. 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

17. Test Machines: TE57

18. 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

19. Combined Results: Friction Coefficient

20. Combined Results: Mean Friction Coefficient

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

22. 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

23. 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