1928 “Insulinde, 82 kn. 1998 Arie Visser, 25 - 33 kn. Rescue boats

TECIINISCILE UN1VERS1TEIT

Scheepshydromechanica

Archief

Mekelweg 2, 2628

D Delft

Tel: 015-2786873/Fax:2781836

1528 'INSLJLINDE"

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tite huit

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being built by

Blanietigiti Shipyard with

Sibirit Shipyard incharge of fitting out. 'Flic basic desigit reqitiremeilts were sea- worthiness in bad weather, minimal draught, limited main dimensions, self-righting with- out active components, unsinkable, capable al' being launched trom a stip'.sav and recovered s'. ithout damane to propellers or rudders. A suitable locatton br stowing itie Zodiac inflat- able was required with the ability to put the intlatabte alloat wi ltu)ut hoisting or other liait- dung. Tite final requirement was to have a fly- ng hrtdge with an upper sieering postimOn

Tite getterai end result can he seen in tite

drawing. Self-righting is by watertight wheel- house and the votutrie of the wheelhouse us such thai wheti the vessel is keel up, tite senti- tatton openings are clear ob' tite water, nie tiew boat will replace an obsolete wooden cratt hut oust ttse the same shed attd slipwuy. Tite launching and recovering proce&lttre is made more difficult by stiallosv water ott the end tu the slip and a rock in alignment with the slip- way so that as soon as tite craft is atittat it has to manoeuvre. Launching is therefore iorwarui and the boat will he recovered sment first. which implies good prmttection for the stcrrt near tn case ob erounding utunne recovery.

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E angeù.a Lange in der KWL Breite (KWL) Breite 0. a Tiefgang (Konstruktion) Verdrängung, 100% Zuladung Geschwindigkeit Reichweite bei kn Antriebsanlagen: Mitte:

I X MTU Diesel Diesel 12 V 396 TB 93; Leistung: 1200 kW (1633 PS)

Seiten:

2 X MWM Diesel TBD 234 V 12; Leistung: 610 kW (830 PS)

Alle Motoren mit Luftanlassung.

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_{DESLGN.-DEVELOPMNT OF 5AR CRAFT}

Operational parameters were defined and included a

service speed of 18 knots, a range of 200 miles,

accommodation for a crew of 7, space for 16 seated

survivors and 2 stretchers. Navigation equipment_{was to} be extensively enhanced over the previous craft and like ail earlier boats stern-gear and rudders were to be well protected from damage. _{Above all the completed boat} was required to be inherently self righting in the event of a capsize.

being accepted into service in 1983 (Selsey and Relief). A number of modifications were included in subsequent

boats to be built including a steel deck (replacing _the

original _{luminium ¿ioy deck) and modified stern-tube} arrangements (to reduce noise and vibration).

Displacemont is nc'.'í 26 tonnes.

The hull form of the Mersey Class Ufeboats (Fig. 5)

incorporates a conventional round bilre_body which tTslates into a hard chine after body. Thistogether with trim tabs provides the lift necessary to prevent excessive

squatwhich would be inevitable had the hull form been

of the round bilge type throughout. At 14.25 tonnes dis-Tement Mersey Class Lifeboats have a speed of 16.50 knots - a speed/length ratio n excess cf 2.5 (Table 1).

Adequate bow height and flare to provide lift during launching is required for carriage launched lifeboats. To

optimise these requirements and limit the reduction of forward vision from the recessed wheel-house _reverse

sheer was introduced at station 8.5.

The early

trials carried out on the Experimental Prototype' were not encouraging. The trials speed was

disappointing and although the manoeuvring

character-istics öfffl

135Ï eptble, course stability was

not. Subsequent modifications to the hull form corrected

the initial

problems and production of the

new fast carriage boat proceeded (Ref. 5). The first ten of the

class were built from aluminium alloy, the remaining 27 were constructed from advanced composite materials. At a speed/length ratio in excess of 2.50 a soft chine form throughout would, as subsequently demonstrated, have been of value, however the Mersey Class Lifebcats have performed satisfactorily in all weather conditions. 3.3.4 The Fast Afloat Lifeboats

During the early 1980's it was necessary for the RNLI to

provide a small afloat lifeboat. Enquiries were initiated

and trials carried out on a number of proposed _craft.

Ultimately the 33' 0 (Tucker) designed work-boat built by Lochin Marine was selected as being able, when_modified,

to satisfy RNLI requirements. _{Following a period of}

development 12 Lochin 33's were built as the Brede Class

Lifeboat.

The hull form of this craft is of ihe 'Soft Vee'_{typo (Fig.}

4) incorporating three spray rails and a chine rail and a

departure from usual RNLI practice for 'Afloat Boats'.

Considerable numbers of fast work boats and fishing _craft incorporating this type cf hull form have been built.

The Brode being the smallest of the Afloat Boats was

classed as an Intermediate lifeboat and had service

restrictions placed upon it. Never the less the Eredehas

performed well and on occasions in weather in _{excess of} its service limitations.

The Trent and Severn Class lifeboats are the latest

afloat lifeboats to be built and will ultimately replace all

the 13 knot Waveney and 18 knot Arun class lifeboats. The design for these two new craft was started in 1989

after fully considering the staff requirements which _are

summarised above.

Preference for a round bilge hull form was expressed

however the speed/ length ratio of these boats required

that a 'vee' type hull form be considered. _Resistance,

propulsion and instrumented sea keeping tést were carried out on 117,hscale models built to the hull ines drawn for

a round bilge and a 'soft veo' hull form. The results

favoured the 'soft vee' hull form (Ref.

6) which was

adcpted for both the Severn and Trent Class Lifeboats.

The 'lines' for these boats are shown in Fig. 7 the hull

form of the Trerit being geometrically similar to that of the

Severn. The influence of the 'Erede' and earlier pilot

vessels can be seen while the arrangement of the tunnel and side keels devolve from the Mersey and Tyne Class lifeboats. These provide rudder and propeller protection

and enable the boat to take the ground. A 5 wedge _s

incorporated into the aft end of the tunnel and trim tabs

are fitted to the transom cut-board of the tunnels. The

fore body lines are conventional. A down-angle chine rail

to control wetness is included throughout. _{A short,}

additional spray rail is fitted forward for the same reason.

To assist the recovery of survivors from the water the sheer line is swept down to a point 850mm above the waterline 1.50 metres aft of amidships and to improve

forward vision reverse sheer is introduced at station 9.

4 PERFORMANCE

4.1 SPEED

lt is necessary for a lifeboat to be able to respond to an

emergency call-out as speedily as 'conditions' will allow

in order to be effective in search and rescue and in the saving of lives. Earlier lifeboats, such as the Watson, Oakley and Rother might (now) be considered slow,

however, they were, at a speed/length ratio of between 1.20 and 1.35 (Table 1) as fast as any displacement craft then built or likely to be built.

Displacement speeds, ranging from 9 to 11 knots were long been considered adequate and weight, which is

totally non-productive in the search for speed, to be vital for a rescue craft to be successful. These philosophies, and the hydrodynamics of displacement craft have limited

an earlier increase of relative speed for All Weather Rescue Craft in the UK.

The development of the inshore lifeboat did not, however

suffer completely from these limiting philosophies and

were able to achieve speeds of between 20 and 30 knots

(or more) well ahead of their larger cousins, Inshore

lifeboats did, however, have weather limitations_imposed

on them. This did not, however, reduce their effective-ness, as a rescue craft except in all but the _{severest of}

weather conditions.

Fast rescue and service craft were successfully developed during the 1930's principally by the Royal Air Force and in

1929 the RNLI built a 640"

_{(19.50m), 17.5 knot fast}

rescue launch (See Table 1). This craft was stationed at Dover to cover the growing cross channel ferry system. lt seems however, that no attempts were made to

capital-ise on this early experience _{or from the experienced}

gained by the RAF from the operation of the fast rescue and service launches.

The advantages of speed, and the power that came with it, were to remain untapped by both pilot boat and rescue craft operators until the early/mid 1960's when the RNLI introduced the 13 knot Waveney Class lifeboats and the

Pilot service (Trinity House) introduced the 18/20 knot

Vigia' to the Nab Station (Ref. 7)

The power installed in SAR and pilot craft to enable these higher operating speeds to be achieved s now available for other uses. _{Bollard performance has improved to the}

extent that towing, once considered _{un-necessary for} rescue craft, has taken its rightful place in

_{the list of}

'Staff Requirements'. _{The manoeuvrability of UK pilot} and rescue craft has also improved with the availability of additional power.

4.2 _SEAKEEPING

t _{has been stated that 'seakeeping}

_{'is the ability to}

maintain good forward speed in bad weather. Whilst the

ability to do this

is _{important, there are many other}

aspects of this complex subject to be considered in the design of pilot and rescue craft.

Of significant importance is the ability for the craft to run before heavy weather without broaching. Because of the

similarity of their work it _{is important that both pilot}

and

rescue craft can do this.

Other components in the _{'seakeeping' formulae include} dryness, aeleration, platform stability,_{and resistance to}

capsize.

Early RNLI craft were provided with drogues whichwere

streamed to prevent broaching when running or working

in heavy following seas. These boats were the 'slow' 8 to 10 knot boats some of which were fitted with single

rudders mounted on the sternpost others with twin rudders fitted in tunnels to protect them (and the propellers) from

damage. The drogue prevented the boat from 'surfing'

in the face of the approaching

_{waves. The limited}

influence that these inefficient rudder arrangements had on the directional stability of the boat in these conditions, was negligible and the effect on the boat dangerous. Although some of the later boats have been provided with drogues, the increased speed, the improved hull form and vastly superior steering arrangements have substantially overcome the need for this equipment to be used in heavy

12

2

weather. The Arun class boats _{which are not provided}

with drogues are fitted with power steering (H.O to H.O in

4/6 sec's.) and large (31/2% L.A.) _{twin spade aerofoil}

rudders which operate in 'clear water' reduce the risk of broaching.

Full scale and model tests have demonstrated the chine' hull form (Ref. 6) to have advantages over a round bilge

hull form and both benefit from_{large 'Radii of Gyration'} (greater than 0.25L - Ref. 5) in adverse weather and

following sea conditions. _{Detailed consideration of the} underwater appendages is also ofvalue.

Current designs of rescue craft and pilot boats with their higher speed, cleaner underwater hulls, reduced

deadwood, and improved steering gear arrangements are better equipped to perform adequately in following sea conditions than their predecessors,

Greater importance is now being placed on the need for lower acceleration (and noise) in crew spaces in order to reduce 'crew fatigue' and structural damage at the higher

speeds. Similarly greater efforts

_{are being made to}

reduce wetness from spray since good forward vision is

essential at higher speeds. _{Tank tests and full scale}

evaluation trials are being undertaken to seek improve-ment in these areas.

Of importance to both rescue craft and pilot vessels is the need for good platform stability when stopped or nearly

stopped in the water along-side other _{vessels or when} picking up survivors from the

_{water. Tpical values for}

GM of UK rescue craft is between 0,08L and 0.09L. The ratios of length to beam for both types of craft are similar with larger ratios applying to older craft or larger vessels (See Table 1).

The controversy within the RNLI _{to build selfrighting or}

non self-righting rescue craft has long been _resolved.

This has lead to the building of craft with a smaller length to beam ratio and greater initial stability than was provided

in the past (Ref.8) giving greater resistance to

capsizing. _{Self righting is provided by the watertight} superstructure.

The required standards of positive stability for rescue craft vary from authority to authority. The RNLI require_positive stability, including that provided by the superstructure, for

a range of 180°. Some rescue authorities _{accept less}

than this, others require self righting with the wheel-house flooded. _{Pilot vessels must have adequate stability to} satisfy the statutory requirements of the country in which they operate.

4.3 _{MANOEUVRABILITY}

Good directional stability and high manoeuvrability are in

contradiction to one another but are and have been

necessary characteristics of both rescue craft and pilot

vessels. With the power now installed for today's boats to achieve higher speeds, both 'alongside' and manoeuvr-ing at sea is easier and considerably less dangerous than was previously the case.

Power to weight ratios have substantiaUy increased (Table 1) as has rudder efficiency and although

super-structure height has been raised, bow thrusters are now

available for small craft which limit the effect of the

resultant 'windage' problems. This is particularly relevant when the craft are stationary, or nearly so.

A contribution towards the better manoeuvrability of

today's craft is the effect given by improved engine control systems and the 'speed of response' of the modern high

speed diesel to the Coxswains changing needs. Some back-driving' and/cr 'stalling' of the main engines, has,

however, been experienced on the Tyne class lifeboats

when manoeuvring in bad weather. This has been

overcome by the fitting of electronic engine governing or an additional seal on the fuel pump assembly.

The fitting of controllable pitch propellers would reduce the

risk of this problem and ensure thrust, both ahead and

astern, at all times. Presumably, high initial and mainten-ance costs (particularly propeller damage) mitigate against

the more frequent use of this equipment. The cost of

wear and tear on both gearbox and engine from extreme marioeuvring is not, however, apparently considered.

5 CONSTRUCTION

5.1 MATERIALS

Wood, steel, aluminium alloy, and glass reinforced plastic

(GRP)/composites are materials which have been and,

with the exception of wood and steel are still being used

for the construction of lifeboats and pilot craft.

The

decision to uso one material in preference to another

depends on the owner's 'operational parameters'. lt is unlikely, unless high tensile steel is used in place of mild steel, that an adequately low construction weightcan

be achieved to guarantee the displacement associated

with a high speed rescue or pilot craft.

The use of wood for the construction of fast pilot vessels ended during the 1960's, however, it continued to be used

in the building of some lifeboats in the UK until 1983.

Wood was used for the construction of a number of proto-type craft for the RNLI (Arun and Medina) but it is unlikely

to be used again for series production. Initial cost for suitable grades of timber is high. Adequate numbers of craftsmen both for construction and maintenance _are

difficult to locate further adding to initial and maintenance

costs. _{Moreover with the demand for ever increasing}

performance low weight with adequate strength is difficult to achieve when timber is used for the construction of fast

craft,

The materials more usually used for the construction of

rescue craft and pilot vessels are aluminium alloy and

'Composites'. The use of Aluminium alloy for the building

of _pilot

_{and rescue craft apparently enjoys greater}

Popularity in Europe than in Britain (10 Mersey, 10 pilot [Ref. 9]) where a very small percentage (6%) of the total

number of these craft (reviewed) in operation _{are built}

from this material. _{Construction and possibly}

mainten-ance costs are higher than GRP when comparing similar sized vessels. There is also a strange reluctance to accept or understand the benefits of the material in a

marine environment when the construction of small craft is considered. This is not the case in Europe, Americaor

Canada where a large number of pilot and rescue craft

are in service or under construction.

The construction of small craft from glass reinforced plastic materials (GRP) began during the 1950's. Since that time the popularity of the material for boat building

has grown such that almost ail UK pilot and rescue craft delivered today are of GRP or composite construction. The problems of Osmosis are now well understood ¡f not eradicated as ¡s the need to provide additional strength to the shell and deck in way of the shoulders and boarding areas. Fendering arrangements have improved as have

the means of securing deck and skin fittings to limit or

prevent the ingress of water.

A matter of great debate is the repair of major damage. It is reasoned that as there are abundant facilities to

repair steel and to a lesser extent aluminium alloy these

materials ensure relatively quick and less costly repair

should major damage occur. However, the ease with

which a portion of a hull or deck can be moulded to

replace the damaged section, substantially off-sets the high costs associated with the conventional repair of

major damage to a GRP vessel.

The use of advanced composite materials such as epoxy resins, carbon, kevlar etc., for the construction of rescue craft is growing as a direct result of the need to achieve higher performance (speed). The weight advantages over competing materials on the basis of equivalent strength are shown in Table 2. There is however a cost penalty

(Table 2). The initial and through life costs for reduced installed horsepower to achieve equivalent speed are

seldom evaluated.

The construction of vessels using advanced composite

materials needs to be undertaken with some care.

Vacuum bagging and oven curing are relatively costly

processes to install and operate which add to the cost of vessels built from these materials. Damage repair can be

relatively inexpensive but is dependant on the extent of

the damage.

The use of 'jigs' to construct either steel or aluminium alloy hulls for small craft is common as is the use of a

female mould for the construction of a GRP hull. The con-struction of vessels from advanced composite materials can be achieved using a male plug (jig) or a female mould and is dependant on the number of boats required.

5.2 SUBDIVISION

Search and Rescue Craft are comprehensively subdivided to limit the ingress and free flow of water in the event of

major damage. Early lifeboats were also provided with

'air-cases' to provide enough buoyancy to float the

vessel should all compartments be flooded. The modern lifeboat derives buoyancy from the 'sandwich' shell and

TABLE i

23A

F.D. HUDSON

NavALAQ.c TrCX

GOT HE.H BURE- 7NTE4. CoNF tRC.E 4

ES N

DE.V Lrt-MT QAU.At1

14

RESCUE CRAFT

No BOAT TYPE DIMENSIONS

L B D d RATIOS

LIB B/D Did

DISP. tonnes V knots Fn BHP K

DIL.

i Liverpool

10.8 3.3 0.7 0,53 3,27 4,65 1.34

8.30 7.2 0,364 36 3.48 187 2 Watson

14.3 3.9 1.7 0.84 3.67 2.29 2.02

24.50 9. 0.390 140 3.76 237 3 48' Oakley

14.8 4.3

1.7 1.05 3.44 2.49 1,65

31.50 9.

0.384 220

3.41 275 4 SoIent

14.8 4.3 1.7 1.05 3.44 2.49 1.65

28.50 9.

0.384 220

3.24 249 5 Barnet

15.8 4.1 1.8 1,05 3.85 2.28 1.71

28.50 9. 0.373 140 4.06 205 6 37' Oakley

11.3 3.5

1.3 0.65 3.23 2.69 2.00

12.00 8.. 0.390 100

2.77

236 7 Rother

11.3 3.5

1.3 0.65 3.23 2.69 2,00

13.00 8. 0.390 100 2.88 255 8 64'FLB

19.5 4.3 2.1 0,93 4.57 2.00 4.67

27.50 17.5 0.653 750 3.35 105 9 Mersey

11.8 3.8 1.8 0.95 3.09 2.09 1.92

14.25 16.5. 0.790 .51Q 2.61 246

10 Waveney

13.5 3.7 1.9 1.08 3.65 1.90 1.81

18.00 14.5' 0.650 520 2.70 207

12 Thames

15.3 4.4 2.41.15 3.48 1.85 2.08

29.00 18.

3.757 780

3.47 229 13

14.3 4.3 2.2 1.07 3.33 1.97 2.04

26.00 17,5 0,760 850 3.06 252

14 Arun

15.9 5.2 2.3 1.28 3.06 2.26 1.80

33.00 18. ' 0.742 970 3.32 232 15 Trent

14.0 4.6 2.0 1.15 3.04 2.34

1.71 28.00 27 1.186 0 3.44 289 16 Severn

17.0 5.6 2.6 1.37 3.04 2.20

1,86 38.00 25.

0.998 2300

3.21 219

17 Brede

10.0 3.5 1.9 0.80

2,86 1.87 1.97

9.00 19 0.989 410 2.82 255

18 Medina

10.8 3.7 1.0 0.76 2.92

3.70 1.25

9.25 25. 1.252 700 2.87 ' 208 FI Canot 1

17.6 4.0 2.0 0.93 4.40 2.00 2.15

22.50

0,864 752

3.81 117

F2 Canot 2

15.5 4.0 1.7 0.71

3.88 2,35 2.39

20.00 21. 0.876 752 3.42 152 F3 13.30 13.3

3.0 1.9 0.71 4,43 1.58 2.68

22.00 15. 0.676 711 2.64 265 F4 10.44(1) 10.4

3.2 1.7 0.60

3.25 1.88 2.83

7.50 23.: 1.174 485 2.86 189 F5 10.44(2) 10.4 3.2

1.7 0.60

3.25 1.88 2.83

7.00 23. 1.174 485 2.76 176

Dl 2331

23.3

5.5 2.6 1.60 4.24 2,12 1.63

63,00 17.5

0.596 1500

3,59 141

D2 19.99

20.0

5.6 2.7 1.80 3.57 2.07 1.50

68,00 11.5' 0.423 766 3.43 241 D3 15.10 15.1

4.7 2.6 1,70

3.21 1.81 1.53 38.00 IO. 0.423 334 3.37 312

D4 10.50

10.5

2.9 0.9 0,60 3.62 3.22 1.50

6.00 35. ' 1.176 600 3.50 147 D5 9.22 9.2

2.4 1.0 0,60 3.83 2.40 1.67

4,00

26. 1,410 306 2.92 145 D6 16.50 16.5 32,00 23.

0.933 1000

4.11 202

Nl J.F:'

15.6 4.8

0.85 3.25 16.00 35.

1,457 1400

3.74 119

N2ValentIjn

10.6 3.8

0.75 2.79 9.20 34.

1.714 900

3.44 219

Si

16m

16.2 5.2

1.65 3.12 25.00 34.

1,389 1350

4.63 166 S2 Victoria

12.1 4.9

2.47 11.40 32. 1.514 800 3.82 182

Cl

100

12,4 4.1

1.24 3.02

21.00 26. 1.386 637

4,72

312 C2 200

23.2 7.6 3.6 2.50

3.05 2.11

1.44 179.00 10. 0,343 750 4.89 406 C3 300

13.5 3.9

1.10 3.46

17.90 12.

0.536 500

2.27 206 C4 300A

15.8 5.2 2.1 1,40 3.04 2.48

1.50

29.50

18.

0.745 1070

2.99 212 C5 300B

15.8 5.2 2.1

1.40 3.04 2.48

1.50 29.50 21.

0.870 1170

3.33 212 C6 Arun

16.3 5.2 2.3

1.50 3.14 2.26

1.50 31.50 18. 0.733 970 3.24 206 C7 400

21.3 5.6 3.3

1.30 3.81 1.70

2.54 55.00 20 .

0.712 1300

4.11 161

Gi

Res. Cruiser 26.7 5.6 2.4

1.60

4,76 2.33

1.50 81.00 24.

0.763 2350 4,46

121 G2

Res. Cruiser 18.9 4.3 1.9

1.26

4.40 2.26 1.51

30.00 16. 0.605

890 2.94

126 G3

Res. Cruiser 23.3 5.6 3.3

1.45

4.16 1.70 2.28

57.00 20.

0.682 1750

3.61 127 G4

Res, Cruiser 27.5 6.5 3.4

1.63

4.23 1.91 2.09

100.00 24.

0.754 4500 3.58

136

Iceland I V 26

7.9 2.5

0.94 3.16 25. 165 Iceland 2 Osborne

7.7 2.6

1.17 2.96 25. 165

K = V/(BHP/Displ) D/L = DispV(0.OIL)

L = Length Overall in feet B = Breadth Moulded D = Depth Moulded

d = Draft Moulded

TABLE 2 (Ref. 11)

TABLE 3

Construction Material

_{Structural Weight}

%age

Unit Cost

£lSq.rntr.

Aluminium alloy _{100 50}

Polyester CSM/WR Single Skin _{105-120 29} CSMiWR Pclyester/Vinylester Balsa Core 90-95 44

Glass/Aramids/Foam Core

78-82 70

Carbon/Foam/Honeycomb Core _55-65

Steel _150-200

ITEM _{STRUCTURE MACHINERY OUTFIT ELECTRICS DWT}

LOAD

%age

33 27 23 5 12 100 Iceland 3 Dutch

20.4 4.2 2.0

1.40 4.86 2.10 1.43

57.0 ₂₈₀

Iceland 4 Pacific32 9.5 3.2

0.75 2.97 9.0

25.00

360

Iceland5 Alusafe

13.6 3,8

1.10 3.58 19.0 33.00 1.478

500 6.43

214

US I

SurfRes.

14.6 4.2

1.26 18.3 27,00 1.162

840 3.99

167

PILOT VESSELS

I Vigia

12.6 3.7

1,00 3.41 3.70

I0,0

20.00

0.927 300

3.65 142

2 Dublin

13.1 4.1

3.20 14.5

21.00

0.954 600 3,26

183

3 D'star D-mark

14.7 4.6

3.20 18,5 3 7,00

0.936 1000 5.03

165

4 Harwich

14.6 4.3

1.26 3,40

27,00

5 Comet

13.0 4.4

2.95 14.5. 20.00

_{0.912 735}

2.81 187

6 Voyager

18.6 6.3 1.7

1.07 2.95

29.3

28.00

1.067 1700 3.68

129

7 Dunlin

15.1 4.2 2.2 1.0 3.60 1.91 2.00

8 Halberdier

15.3 4.8 2.6 1.2 3.19 1.85 2.15

Fn = v/ gL

where y = speed in ftlsec g = 32.2ft/sec/sec L = Length in feet

'in-situ' foam. In some cases air bags are located in void

spaces to limit permeability and add buoyancy. A 'two

compartment standard of subdivision' has been adopted

in the UK for modern rescue craft and where-ever

possible structural and buoyant foam having a total

volume equal to the volume of displacement is provided. Pilot vessels will satisfy the 'subdivision' standards of the

'Authority' under which they are built but are unlikely to

have the number of watertight compartments of a rescue craft.

5.3 NOISE (AND VIBRATION)

Of increasing importance is the need to limit the level of

noise to which the crew are subjected. Most National Governments have indicated or imposed maximum limits for 'manned spaces' which must not be exceeded. lt has

been shown that not only is hearing damaged but _crew

efficiency is reduced after only short periods of exposure

to excessive levels of noise (Ref. 10)

The early lifeboats with low installed engine power and heavy wood construction would have little difficulty in

meeting current defined standards. As power was increased and structures made lighter n the search for speed so 'noise' problems grew. The level of noise on

all but the Tyne Class Lifeboat was acceptable. Although

built of steel the noise levels recorded in _{all manned}

spaces on the Tyne's was unacceptable. This was due, in part, to the limited use of acoustic insulation (to reduce

weight), however, no attempt was made to isolate the main engines from the main structure nor was serious

consideration given to the sterngear arrangements.

Subsequent to a number of modifications including an increase in propeller tip clearance, the fitting of new

propellers designed to reduce blade loading, fairing of the

'A' brackets and the recessing of the 'A' bracket palms

into the hull and the elimination of an external flangeon the sterntube noise levels were reduced. They are not, however, still above acceptable limits.

The design of the Mersey, Trent and Severn class

lifeboats took into account the need to limit noise levels. lt was agreed that 84DbA would be the maximum level for

any manned spaces. In general these limits have been met. To do so all main engines are resiliently mounted, as are exhaust and service pipes, acoustic insulation is incorporated into the structure and in the case of the

Mersey 'Scatra' Flexible couplings are fitted.

The designers and builders

of pilot vessels have

recognised the need to minimise noise level for _some

time,

The need to withstand a capsize or pitchpole

regrettably restricts the use of a resiliently mounted wheel-houses to pilot vessels.

6 _DISPLACEMENT

From Table i it will be seen that the displacement of UK rescue craft is generally greater per unit length than other rescue craft or pilot vessels.

16

The components for

'lightship' and 'load' condition

remain relative and typical values are indicated in Table

3. Both 'strategic' and 'operational requirements' will

influence or modify these ratios.

6.1 STRUCTURE

The structural weight included in the 'lightship' estimate depends on the preferred construction material and the

service conditions in

which the

boat will operate.

Comparative weights for varying materials are as shown in Table 2 and are related to an aluminium alloy structure for a given strength.

6.2 MACHINERY

Machinery weight is dependant on detailed specifications and the preferred choice of main propulsion engines. An approximation of machinery weight can be established

from the following formula - 1 .6[2x(m/e +g/b wt)1 the

result will require to be adjusted for specific needs.

Numerous types of propulsion unit are available for installation in pilot boats and rescue craft. _{The RNLI}

favour a conventional installation although consideration

has been given to the fitting of Water Jet Units and

Controllable Pitch Propeller systems which are now fitted by numerous pilot vessel and rescue craft operators with some success. Some concern s expressed on the

reliability of OFF Units.

6.3 OUTFIT

Outfit weight is totally dependant on operational require-ments. Careful selection cf materials and equipment will limit the unacceptable growth of outfit' weight.

The RNLI now make extensive use of

'soft' fenders glued to the side shell as a means of reducing weight and to limit the transfer of side impact loads into the hull/deck

joint. _{Pilot vessels continue to use 'tyres' hung over the}

vessels side, Inflatable collars fitted around the deck of both pilot and rescue craft have met with greatsuccess as lightweight

_{energy absorbing fenders which add}

to

buoyancy.

The use of composites for internal furniture and 'joinery' work is growing to partly off-set the growing requirement for insulation/buoyancy materials.

6.4 ELECTRICS

The demand for improved electronic navigation and communication equipment has lead to a growth in the

weight and complexity of electrical installations onboard

most rescue craft and pilot vessels when compared to

their predecessors.

Care needs to be taken to limit

'electromagnehc' interference.

7 CONCLUSIONS

The design of off-shore rescue craft has altered

substantially over the last 30 years to meet changing

2L

strategic requirements and operational parameters. Most of these changes have taken place at a measured pace.

The traditional round bilge displacement and

semi-displacement forms which served the IRNLI so well for so

many years are being replaced by the soft 'Vee' form

characteristic of

the new Severn and Trent Class

Lifeboats.

Model tests, prototype evahiation and operational

experience have shown these hull forms to be as 'sea

kindly', if not more so, than the 'traditional hull forms. The installed horsepower required by today's rescue craft

to achieve increased operational speeds has given

improvements in towing and manoeuvring characteristics

which have lead to greater safety for boat and crew. Increased free-running speed, however, requires under-standing, particularly in adverse weather conditions if crew and boat are to remain intact.

Improvements in performance have demanded a

contin-uous review of materials, methods of construction,

machinery, equipment and outfit to limit unnecessary growth in displacement. The displacement of UKrescue

craft is, however, heavier than most other rescue craft or

pilot vessels leading to higher 'impact' loads than are

perhaps necessary.

ACKNOWLEDGEMENTS

The author wishes to acknowledge the help given to him in the preparation of this paper by his ex-colleagues at the RNLI and to the Director for his permission to present it. The generosity of members of the International Lifeboat Federation in making data available for analysis is greatly appreciated.

The views expressed are those of the

Author.

Although the 350" (108m) Medina Class Lifeboat, of deep Vee form incorporating a ski sole and a derivative of the Atlantic 21, had been under development since the late 1970's (Ref. 4) it was not seen as a natural successor to the Oakley and Rother Class Lifeboats. Work

commenced on the development of the Mersey Class

Lifeboat in 1983.

The prototype Medina had been provided with

out-drives' driven by light weight diesel engines and were to prove inadequate for the 'service'. Subsequent Medina Class lifeboats (in all 3 were built) were fitted with water jet propulsion units to enable the boat to be evaluated as a carriage or sllpway launched lifeboat. Beaching trials with water jet propulsion units were not successful nor were subsequent coastal evaluation trials.

Although the development of this class of lifeboat was

stopped in 1985 the basic hull form had been incorporated

into the initial design sketches for the Mersey Class Lifeboats (also Dutch, Swedish, italian, and Chilean

Boats). Model tests were carried out on a planing hull

form similar to that of the Medina Class boats

incorporating deep propeller tunnels and collars.

Preliminary arrangement drawings, design calculations and operational experience obtained from the Mecina Trials, however, confirmed the need to provide a 'full

depth hull form to meet current PNLI requirements.

7

REFERENCES

JAMES, Brian: 'Clearing the name of a lifeboat

cheat', The Times Review, 21 Aprii 19go.

BAILEY, D: 'The NFL High Speed Round Bilge

Displacement Hull Series'. RINA Monograph MTM4

1976.

BAILEY, D: A New RNLI Lifeboat: The Tyne Class

Fast Slipway Boat', RINA Spring Meeting, 1993.

MACDONALD, S et al: 'Rigid Bottom Inflatable

Craft', RINA Small Craft Group Conference, November 1981.

HUDSON, F D: 'Design and Development of the Fast Carriage Lifeboat', Inst. of Marine Engineers,

April, 19go.

HUDSON, F D et al: 'The Design and Development

of Modern Lifeboats', 65th Thomas Lowe Gray

Lecture, Inst. of Mechanical Engineers, January 1993.

SHARP LES, A K et afr. Pilot Launches - Design and Operation.'

RINA Symposium on Small

Craft,

September 1971.

WELFORD, S E: is it right to right?.' The Naval Architect 1974.

CORMACK, D: Pilot Launches - a UK perspective.' Ship and Boat international, March 1995.

WELFORD, S E: 'Noise in RNLI Lifeboats', Quiet

Revolutions Conference, Inst. of Mechanical

Engineers 19go.

11. HARVEY, G et at Advanced Composites Seminar', SP Technologies, 1996.

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¡363

'VNEY

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The hull form (Fig. 4) derved by Ship Dvisibn was typical of the NPL High Speed Round Bilge Displacement Series (Ref.2) having a rounded mid-body, not unlike the

Watson but with higher rise of floor, flared tore body sections and rounded parallel after body sections leading into the wide radiused transom. The higher rise of floor

required the fitting of deeper bilge keels than those

fitted to the earlier slipway boats.

The design and

development of this very suessful lifeboat is described n Ref. 3.

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199

IRENT AND3EVER

Mr Rolf Westeröm is a Swedish Master Mariner who is

currently Managing Director of the Swedish Sea Rescue Institution. He has previously been the owner of a Ro-Ro vessel and oceangoing tug, Master of Ro-Ro ferries and

a Search and Rescue vessel.

He has also been a

fisherman.

1.0 INTRODUCTION

The Swedish Sea Rescue nstitution celebrates its 90th anniversary this year. Since it was founded it has

operated as a volunteer organisation without any govern-ment support.

Our purpose is to own a fleet of rescue boats, to rescue life at sea, to ensure that the Government lives up to the international conventions about sea rescue, and to always work for a better and more efficient national sea rescue.

The Swedish Sea Rescue has 34 stations around the coast and on the three large lakes with over 60 rescue u flits.

The current rescue boats are mainly three types:

Slowgoing steelcruisers with an age of up to 50

years, length 15-17m, speed 9-13 knots. Mainly used for ice situation, (see Figure 1).

Fastgoing GRP boats, length 10-14m, speed 20-30

knots, mainly for use inshore, operating for an 8

month season - no winter months. (See Figure 2). RIB-boats with a length between 5 and 10m, speed 25-52 knots, (see Figure 3).

Four years ago we realised that offshore around the coast we had a fleet of all-weather boats which had an average

age of 38 years and an average speed of 10 knots.

Furthermore the crews did not use the slowgoing steel

boat during heavy weather, always using the fast inshore

boats instead, putting both the boat and themselves at

risk.

From these experiences we have developed, and are

building, two new series of fast rescue boats better suited

SWIDE.N

NEW DESIGN FOR THE SWEDISH SEA RESCUE INSTITUTiON Capt Rolf Westerström

Swedish Sea Rescue Institution

SUMMARY

The Swedish Sea Rescue Institution is currently building a new series cf 12m rescue boats. The new boat is to replace

a sloWgOingsteelcruiser and a fastgoing inshore boat; in other words replacing two units with one unit.

The prototype of the boat being described in this paper has been tested and evaluated and the following describes boat number two in the series. Fifteen boats are planned within the next four to five years.

AUTHOR'S BIOGRAPHY

MAY37- QOTHENBUR

to offshore operation than the GRP boats mentioned

above.

Rescue 1600 is a series of 16m rescue boats being built in epoxy composite and powered by 2 x 675 hp Scania diesel engines connected to

two C/P

propellers capable of a top speed of 32 knots, (see Figure 4).

2.0 THE NEW 12M RESCUE BOATS - DESIGN Rescue 1200 is the second in a new series of rescue boats for the Swedish Sea Rescue Institution with an

overall length of 12m. Some of the demands put forward while in the planning stage for this series

were as follows:

top speed 35 knots minimum; positive stablity all 180 degrees;

Crew seats for four persons at boat's centre of movement;

good behaviour in high seas;

good manoeuvrability at all speed levels; flexible transport room for different tasks; hull strength and robustness;

waterjets connected to two engines.

A speed demand of a minimum of 35 knots was consider-ed essential from the crews' point of view, as over 80% of

the calls answered are to rescue pleasure craft in a

windforce of less than S Beaufort and less than two

nautical miles from the coastline. This means we can average a speed of 30 knots on most calls.

Waterjets were chosen because of speed requirement,

manoeuvrability, shallow water operations and lighter

engine load.

I, t,

The demand for a flexible transport room came from the different tasks our crews are engaged in beyond purely sea rescue, such as hospital transportation from islands

to mainland and carrying portable fire pumps and bilge

pumps.

12m was chosen as the size of this boat so that it would meet the demand of easy handling by all crews (especially ,

an all volunteer crew) and at the same time be,lar

eno ugh to handle all weather calls (except ice cohditjns') around the Swedish coast.

The idea of hull shape and design was taken from the

10.5m Valentine Class of the

Dutch Sea Rescue

Institution, KNRM. Some of their experiences of

inflat-able tubes as opposed to a solid foam fender aided us in

choosing a fender of polyurethane. The design of the

fender is narrow at the bow and widens along the sides covering most of the freeboard.

The boat is built to meet the regulations of Nordic Boat

Standard for Commercial Craft.

The high speed demands of the Rescue 1200 made it

clear from the beginning of the project that the weight had

to be as low as possible without compromising the

strength of the hull. Sandwich composite is the material

used in the construction of the hull, deck, tanks,

motorbeds and bulkheads as well as inner stiffenings. The outer cover is made of multiaxiella Devoid weaves of

E-glas, layered ¡n Jotun Vinylester. The core material is a strong PVC-foam of Divinycell HD-type with very good fatigue and impact characteristics.

The keel is completely protected by polyurethane enabling the boat to be beached while picking up injured people on the small outer islands which do not have any docks and are only visited by pleasure craft during the summer, and aro otherwise uninhabited.

Rescue 1200 D es g n e r Length overall Max beam Depl. Hull Draft Top speed Material Engines Gearbox Jets Control system Emergency system ACKNOWLEDGEMENTS

- The Dutch Sea Rescue Institution, KNAM, for the use

of their Valentine-class blue prints, which aided us in the concept of our own design.

- Naval Architect Rolf Ehasson.

Rolf Ehasson 12m 4. 2m 11 .5t 065m 38 knots Epoxy vinylester

2 x Scania DSI 9, 450 hp each 2 x km 310 Ratio 1.078:1 2 x KaMeWa FF Jet 375

KaMeWa electric manoeuvres KaMeWa

3.0 MACHINERY

The boat is driven by two Scania DSI-9 diesel engines of 450 hp with turbo-intorcooler, connected to two FF Jets 375-s waterjets. These are connected to an IRM 310 gearbox with electronic manoeuvring valve. The shafts

are made of epoxy composite with a weight of 4kg each and endurance of 500 hp.

The shaft eliminates the common jack-shaft and the elastic coupling, which together totalled approximately

40kg per engine.

The jets are angled by two direct drive hydraulic pumps,

one on each main engine. These pumps have variable

displacement which allows a steady flow of oil to the jets

regardless of rpm's. When the engine is at full forward

speed there is no oil flow because the pumps will angle inwards and take minimal effect from the engines. The electronics system is run by three computers which

compute information from the control panels and jets.

There is

one computer for each jet

with the third

computing the information cf both jointly.

Steering, rpm and the controls can be driven separately with one control for each jet or both jets by one control. Waterjets were chosen because they are more efficient than propellers at cruising speed, less loads on engines

while towing, working in shallow waters and very good

manoeuvrability.

To avoid turbulence underneath the hull, all sea water

intakes are placed in the transom.

4.0 TRIALS AND OPERATIONS

The prototype boat was on trial for two months in the

autumn of 1996 and tested in all weather conditions with different crews. The hull showed no sign of damage after hard trials in heavy seas. With heavy sideseas and seas from behind, the boat was able to maintain a speed of

22-30 knots without being too uncomfortable onboard.

However, heavy seas from ahead soon proved that the boat needed a larger ballast tank forward, whih has since been remedied.

The fender system minimizes the amount of water on the cockpit windows but there is still a lot of water that sprays

up around the sterndeck.

This is a problem we are

presently working on.

Top speeds were met but the boat was too stern heavy at a ran 10-20 knots making it a difficult operational

increased the length by

Tl6i arid moved the engines slightly forward on boat

number two.

A lot of the navigational equipment mounted was physically broken during the triais. This had nothing to do with how it was fitted on board putting some questions to the manufacturers.

The electric manoeuvring system needs adjusting before it is satisfactory at all speeds.

RE5CUE-1200 F?ON1 3WEtEJ.1

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Seattle

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Seattle boatyard Northwind

Marine daims to have

developed a design for sma!l,

fast boats ideaf for speciality

fisheries using spocter' boats. k

recently sod three of its SAFE

boats to Goden West Artemia

fcr use on the Great Salt Lake

in Utah.

X M

The boats, measuring 27 x

8.5 feet, are made from 5086

aluminium alloy buUt to US

Coast Guard standards for

all-welded aluminium crew boats.

with seff-bailing, non-skid decks

and weigh4,800 oourds. The

design includefli4 inch bottom

plates, 3/16 inch sides and 'L

decks, 314 inch transom

-Northwind's SAFE spotter

doublers and 3/8 inch stepped

boat Photo by Nei:

bottom shoes to reduce drag

RabinowitL

and draft. Dead rise at the

Mvrid F'isIiipt

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stern is 2Y to enhance rcuN

water_handling.

- Other features include

collars made from ndustria

grade polyurethane. 24 inches

high by 16 inches wide, which

are resistant to chemicals and

ultraviolet lighL

Tne col!ars, which are

fitted to welded charnels or

the sides, absorb impacts and

provide a buoyancy rating of

6,720 pounds.

"You won't find a tougher,

hydrodynamicafy more efficie

hull on the market to go along

with our patented collar

system," said Scott Tucker of

Northwind Marine.

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ValentlJn Class Johannes Frederik Class Johannes Frederik Class Graaf van Bylandt Class Arle Visser Class rime E-913, Alida E-786, Johannes Frederik E-873, Chnstien E-982, Graaf van Bylandt 1996 E-1014, Arie Visser 1995 1987 1993 1060m 1439m 1439m 1520m 1820m hull 1006m 13,65 m 13,65 m 14,60 m 17,45 m 846m 1120m (lw)) 11,27 m (lwl) 11,17 m(lwl) 11,77 m(lwl) 11,84 m 1390m 1400m flotation mt (10)9k tanks, 4 crew) 863m 410m 539m 539m 539m 590m 1julI 3,52 m 4,20 m 4,20 m 4,20 m 4,78 m wl 2,98 m 3,2Gm 3,4Gm

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356m 3,40 m ((WI) 3,4Gm (Iwl) 3,6Gm 384m 406m lotation wI (100% tanks. 4 crew) over allbeam over aIl 2,59 2,67 2,67 2,82 3,09 owl/beam cmi 2,84 3,29 3,29 3,46 3,62 flotation wi/beam flotation ml 2,70 3,17 3,29 3,45 cM 0,7Cm 0,81 rn ((WI) 0,81 m ((w)) 0,81 m (1w)) 0,83 m 'ÖiS m 0.91 m (tk tankr, 4 crew 0,74 m 083m '20% tanks, 4 crew 0,79 m 086m 0,87 m 1,03 m w1 7,91 m3 13,45 m3 13,35 m3 13,82 m3 22,76 m3 :100% tanks, 4 crew) 9,77 m3 14,98 m3 15,64 m3 26,34 m3 (100% tanks, 4 crew) 10,01 ton 15,35 ton 16,03 tori 27,00 ton (100%tanks,4crew) 3,56m1-9,1% 4,46m/-1G,6% 4,91 ml-8,5% 5,81 I-8,5% Volvo Penta TAMD 72WJ (L6) 2x331 kWl2600 rpm MAN D2848 LXE (V8) 2x 500 kW/2300 rpm 2x Desdi PECZ 14-1, red: MAN D2848 LXE (V8) 2x500 kW/2300 rpm - MAN 02848 LXE (V8) 2x500 kW/2300 rpm - MAN D2842 LE408 (V12) 2x735 kW/2100 rpm noi yet decided not yet decided 54,4 kW/Ion shaftower geais - als 2x Hamilton 291 2x KaMeWa 40 S62/6 2x Hamilton 362 2x Hamilton 362 62,4 kW/ton 66,1 kW/tan 65,1 kW/ton peed cvpacïly 1240 Itt. 11GO Itr. 1360 lU'. 149G tr. 6800lit. 6 hours full speed 6 hours full speed 6 hours full speed E-873-3a( E-786-8f) 6 hours full speed E-982-bib 16 hours full speed E-1014-ObOa (preliminary) lines plan E-913-bic E-786-8f je sin. (l-3 26° 260 260 270 'je sin 4 270 260 26° 270 'je sta, y 28° 26° 27° 28° e sto ti 29° 28a 29° 30° 'io sin ;' 330 31° 330 330 'ja sto a 38° 350 40° 380 43° 400 51° 48° bMx..oO i. Odd 00.110g 1*4

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-The ships are driven by water jets. The engine

insta!-lations are identical and n calm water both ships can

reach a speed of 31 knots. The changes in the design of

'iiyAN.DT ere thought to contribute to a better motion

behaviour in rough weather. To verify this assumption a measurement programme was planned and executed.

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17 knots in head waves to 28-30 knots in beam and

following waves. This series comprised of 12 runs.

Most of the speed/course combinations were tested twice.

Each of those test runs was 5 minutes long.

Graaf van Bylandt Christlen Length on waterline (m)

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11.7 11.1

Length over all (m) 15.2 14.4

Beam (m) CWL 5,2 3.2

Draught CWL (m) 0.75 -i s ri

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TRIrI c'1 1AD 9 M 0.75 3

Displacement (m ) 13.i

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Max. Speed at r.p.m. (kn / r.p.m.) 31 / 2300 31 / 2200 Deadrise at station 5 (deg)

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