Chapter 3 Works
3.4 Quality Control
I.3
3.3.5 Ventilation facilities are to be so arranged that the curing process of laminates is adapted without any bad influences.
3.3.6 Shops lighting is to be adequate but not to accelerate the cure of resin. Suitable means of shielding the skylights and windows are to be provided so that lamination and curing process are not exposed to direct sunlight.
3.3.7 Sufficient scaffoldings are to be arranged so that lamination work can be carried out without operator standing on surfaces where lamination is taking place.
3.4 Quality Control
3.4.1 The works is to have an efficient system for quality control to ensure that the product quality meets the specific requirements.
3.4.2 Quality control system shall be formalized through containing following objects:
(a) Organization and responsibility of quality control.
(b) Production guidance and workmanship.
(c) Procedures for inspection and test.
(d) Documentation and records of all quality related activities.
3.4.3 The quality control system shall at least comprise inspection and control routines for the followings:
(a) Raw material procurement and quality.
(b) Storage conditions for raw materials.
(c) Environmental conditions during manufacturing.
(d) Production procedures.
(e) Workmanship.
(f) Compliance with specification and drawings.
(g) Testing.
(h) Finish inspection.
3.4.4 The system shall also include methods for corrective action in case of deviations from the specified standard.
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I.4
Chapter 4 Moulding
4.1 General
4.1.1 The requirements in this Chapter are applied to the FRP moulding techniques of hand lay-up and spray lay-up methods. The moulding methods other than those specified above are to be in accordance with the discretion of the Society.
4.1.2 The moulding of FRP is to be carried out under appropriate environmental conditions by competent workers.
The work is to be carried out in accordance with approved procedure under adequate supervision.
4.1.3 It is Recommended that the structural members are moulded in one body with the hull laminates before they advance in cure. However, the structural members separately moulded may be bonded to hull laminates afterward with proper design and treatments.
4.2 Environmental Conditions of Moulding Shops
The requirements of environmental condition as specified in 3.3 are to be complied with during FRP moulding.
4.3 Gel Coats
4.3.1 Gel coat resins are to be applied as an even film about 0.5 mm in thickness, and may be of one or two- coat application by either spray, brush or roller.
4.3.2 The time interval between application of first, second gel coats and next layer of reinforcement is to be within the limits specified by the material supplier. It is recommended that each coat or layer is to follow closely without undue delay.
4.4 Manual Lamination
4.4.1 Laminates are to be free from defects, such as voids, blisters, delamination, resin starved areas and undue concentration of resin.
4.4.2 Fibreglass reinforcements are to be so arranged to have seams as few as practicable. The seams in the same layer are to have overlaps not less than 50 mm. The adjacent overlaps of various layers are to be at least 100 mm apart from each other.
4.4.3 Resin is to be applied on each layer of reinforcement having the layer thoroughly impregnated.Gas bubbles in the resin and air pockets in the laminate are to be driven out by degassing rollers or rubber pallets. Rolling of the layers are to be made carefully and keep glass content proper. Excessive squeezing of resins is not desirable and care is to be taken in confined areas, sharp corners and transitions to avoid excess resin areas.
4.4.4 In laminating, the glass content (ratio in weight) is approximately 30% in case of chopped mats or 50% in case of woven roving.
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I.4
4.4.5 The quantity of curing agents and the time interval between application of each layer of reinforcement are to be kept within the time limits specified by the material supplier. For thicker laminates, care is to be taken to ensure the time interval sufficient to avoid excessive heat generation.
4.4.6 The laminating of final ply is to be carried out by suitable means to provide complete curing of the surface.
4.5 Spray Moulding
4.5.1 Moulding by spray lay-up is the method of moulding by spraying resin and fibreglass reinforcement simultaneously. Moulding process using this method is subject to special approval.
4.5.2 The equipment used for spray moulding is to give an even and homogenous glass content and mechanical properties of the laminate. Spray moulding is to be carried out by skilled operators.
4.5.3 When even application over the spray moulding surface with laminate of certain suitable thickness, regular rolling of the spray-on layers is to be carried out to ensure adequate compression and removal of air bubbles.
4.5.4 Where spray lay-up adjoins hand lay-up, continuity of strength of the laminate is to be ensured.
4.6 Sandwich Construction
4.6.1 Sandwich constructions are fabricated either by lamination on the core material, application of the core against a wet laminate or gluing the core against a cured skin laminate.
4.6.2 Bonds between the skin laminate and core and between the individual core elements are to be made effectively in association with shear or tensile properties. All joints are to be filled with resin, glue or filling material.
In non-structural panels, the butts and seams of cores need not be bonded but should be staggered.
4.6.3 When the core is applied to a skin laminate, the surface is to be a wet reinforcement of chopped strand mat of 450 g/m2 in plane surface and 600 g/m2 in curved surface. Otherwise or when a prefabricated skin laminate is glued to a sandwich core, measures are to be taken to evacuate air from the surface between skin and core.
4.6.4 Sudden change in thickness or any discontinuity of strength between sandwich laminates and adjacent solid laminates is to be avoid. Change in core material thickness is to be made by a taper not less than 1 in 3.
4.7 Curing and Mould Releasing
4.7.1 Mouldings are to be kept for at least 48 hours at an air temperature of minimum +18°C that effective curing can be achieved. Where post curing at higher temperatures to short curing time is intended, the procedures are to be approved by the Society.
4.7.2 Mouldings are not to be removed from the mould until a satisfactory state of cure has been attained to avoid subsequent distortion. Mould releasing operation is to be carefully carried out to prevent permanent deformation or damage harmful to the laminates. The released laminates are to be properly supported so that they may subject to uniform force.
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I.5
Chapter 5
Connection and Fastening
5.1 General
5.1.1 The lay-up of laminates forming hull, deck, tanks, bulkhead and structural members is to be either by primary or secondary bonding depending on the size of moulded unit and working procedure. Laminating is to be carried out as a continuous process, as far as practicable, with the minimum delay between successive plies.
5.1.2 Internal stiffening members, structural bulkheads, etc. are generally secondary bonded to the hull. Secondary bonding is the application of laminating on structure surface which is effectively cured.
5.1.3 The connection of various moulded units into assemblies and connection of any fitting to main structure can be of bonded joint, mechanically fastened or both types.
5.2 Matting-in Connection
5.2.1 The surface ply of a laminate subject to secondary bonding and the first ply of the bonding laminate is normally to be of chopped strand mat. The cured surface in way of secondary bonding is to be ground and properly treated to obtain a surface free from oil, stain, wax and dust. A generous coat of resin is to be applied to the cured surface and the first ply laid on and further resin applied. Bonding is to be carefully executed so as not to cause shrinkage or deformation due to excessive exothermic effect.
5.2.2 T joints are normally to be used in matting-in connection of structural members. Double angles of the joints are to be applied with layers of reinforcements. Where adoption of T joints is difficult due to accessing the reverse side can not be achieved, matting-in single angle as L joints can be used provided it is suitably increased in width and thickness.
5.2.3 The aggregated thickness of matting-in laminates and overlap dimensions of T joints are to be in accordance with Fig. I 5-1A to 5-1C. In order to reduce effect of shrinkage, a small gap is leaving between the stiffening member and the laminate. The gap is filled with resin putty or compressible materials such as plastic foam, etc.
5.2.4 Further examples of matting-in T joints are shown in Fig. I 5-2A to 5-2E. These sketches apply to members constructed of single skin or sandwich laminates as well as to internal members of plywood and timber materials.
(a) Fig. I 5-2A is a typical connection of a member which are subjected to considerably heavy load or vibration, such as engine girders, bulkheads, etc. Shell laminates are to be matted with extra plies of reinforcement to increase thickness in way of the connection and to distribute the load that the member is bedded down on wet reinforcement, with suitable resin mixture if necessary.
(b) For members other than specified in (a), connections such as shown in Fig. I 5-2B and 5-2C may be used.
Low density foam core or resin pastes is to be applied to the square corners.
(c) For plywood and timber members, a coat of thin primer resin is to be applied to the contact area prior to laying-up the matting-in laminates in order to improve the bond quality of the connection. Holes with appropriate pitch may be drilled along the bonding area and reinforcement pushed into the holes to form a key as shown in Fig. I 5-2D.
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I.5
(d) Fig. I 5-2E is a member bolted to a double angle T joint. The connection is formed by laying-up a single angle against a suitable template, which is then removed and further angle laid up against the first one.
5.2.5 Butt joints are not permitted in the shell laminates. In the joints of deck laminates or in case of repair where butt joints are locally provided, the joints are to be so designed that the resin bonding is subject to shear and therefore lapped joints with large bonding area are preferred. Lapped joints can be improved by overlaying with suitable reinforcement. Where the bonding might be sustained a tension, the scarf joints are recommended to use, however, butt joints may be adopted subject to overlay one or preferably both sides of the joints with additional reinforcements.
5.3 Mechanical Fastening
5.3.1 Mechanical fasteners may be used for connecting laminates to each other or attachment of metallic fittings to laminates. Fasteners such as bolts, screws, rivets, etc. are to be of corrosion resistant metal or to be properly protected against corrosion.
5.3.2 Metal fasteners are to be affixed vertically to the laminates as far as practicable and to be dipped with activated resin along with the fastening holes.
5.3.3 Bolt diameter is to be approximately equal to the laminate thickness. The distances between the center of each bolt hole and the edge of laminates are not to be less than three times the diameter of the hole. Bolts and nuts are to be fitted with washers on either side of the laminate.
5.3.4 Self-tapping screws can be used for connection of lightly loaded items where a better type of connection cannot be employed. If the laminate is insufficient to give enough penetration and holding power, the screws are to be screwed into a metal tapping strip or equivalent.
5.3.5 Laminates fastened by cold driven revits of steel, alloy or copper are to be fitted with washers or strips under the head and point of the rivet. the washer is to be of the same material as the rivet.
5.3.6 Where sandwich panels constructed with cores of hard plastic foam are connected by bolts, screws, rivets, etc.
piercing through the panels, well seasoned timbers or plywoods are to be inserted in such parts of the cores in advance.
5.3.7 Where mechanical fasteners are used in way of a location required to be watertight, suitable means are to be taken to ensure the watertightness.
5.4 Attachment of Metal Fittings
5.4.1 The metal fittings may be bolted to laminates in conventional manner or may be bonded and matted-in by layers of reinforcements.
5.4.2 Bolting through the hull is to be avoided as far as possible or kept to a minimum. The size of the holes is to be just sufficient to carry the bolt and which can be dipped in with activated resin.
5.4.3 Metal plates can be moulded into the laminate of structure members or matted-in on the reverse side of structure members to take heavy loads from the fittings. The plates are to be beveled and to have sufficient surface area in contact with the laminate.
5.4.4 The laminate in way of deck fittings such as bollards, eyeplates, deck blocks, etc. which may carry a considerable load, is to be increased in thickness to prevent damage caused by heavy loading. Fittings are to be bedded down on a flexible sealing compound or neoprene gasket to ensure watertightness.
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I.5 5.4.5 A special consideration is to be paid to the installations and reinforcements of fishing gear.
T > t
not less than 6t or 40 mm, whichever is greater
not less than 8t
T t'
t'
t
not less than 6t or 40 mm, whichever is greaternot less than 8t
t' is thickness of overlap but not to be less than t/2
Fig. I 5-1A
Dimensions of Overlap of T-Joints
Resin putty
Tracking with rounded-up
Not less than 25 mm Not less than 25 mm Not less than 25 mm
(a) Solid lines indicate chopped mat layers and dotted lines indicate woven roving layers.
(b) Woven roving layers are not to overlap each other.
(c) The first and final layers are to be a chopped mat layer.
Fig. I 5-1B
In case Chopped Mats and Woven Rovings Jointly Used
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I.5
Resin putty
Tracking with rounded-up
Not less than 25 mm
Not less than 25 mm
Fig. I 5-1C
In case Chopped Mats Used
Shell laminates are increased in thickness at the connection with structural member
Fig. I 5-2A
In case Consideration to be paid to Load or Vibration
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I.5 Plastic foam, etc. is inserted
between structural member and laminates
Mat-overlay
Mat-in
Fig. I 5-2B
Standard Form of T-Joints
Filled up with resin putty, etc.
Fig. I 5-2C
Standard Form of T-Joints
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I.5
Plywood or timber
Reinforcement pushed
Filled up with resin putty, etc.
Fig. I 5-2D
Typical Matting-in Connections of Structural Members
Members bolted to double angle connection Not less than
three times bolt diameter
Fig. I 5-2E
Typical Matting-in Connections of Structural Members
RULES AND REGULATIONS FOR THE
CONSTRUCTION AND CLASSIFICATION OF SHIPS OF FIBREGLASS REINFORCED
PLASTICS 2017
PART II – HULL CONSTRUCTION
April 2017
RULES AND REGULATIONS FOR THE
CONSTRUCTION AND CLASSIFICATION OF SHIPS OF FIBREGLASS REINFORCED PLASTICS
PART I GENERAL REQUIREMENTS 2017
PART II HULL CONSTRUCTION 2017
PART III EQUIPMENT AND FITTINGS 2017
PART IV MACHINERY INSTALLATIONS 2017
PART V ELECTRICAL INSTALLATION 2017
List of major changes in Part II from 1998 edition
12.1.3 Amend No.1
RULES AND REGULATIONS FOR
THE CONSTRUCTION AND CLASSIFICATION OF SHIPS OF FIBREGLASS REINFORCED PLASTICS
2017
PART II
HULL CONSTRUCTION
CONTENTS
Chapter 1 Shell Laminates... 1
1.1 Construction and Arrangement ... 1 1.2 Scantlings ... 1 1.3 Weight of Fibreglass Reinforcements and Thickness of Laminates ... 2 1.4 Scantling Reduction for Service Restriction ships ... 3Chapter 2 Longitudinal Strength ... 5
2.1 Application... 5 2.2 Section Modulus ... 5 2.3 Moment of Inertia ... 5 2.4 Calculation of Section Modulus ... 5 2.5 Continuity of Strength Materials... 6Chapter 3 Shell Laminates... 7
3.1 General ... 7 3.2 Keels ... 7 3.3 Shell Laminates for Midship Part ... 8 3.4 Shell Laminates for End Parts ... 9 3.5 Side Shell Laminates in Way of Superstructures ... 10 3.6 Local Strengthening of Shell Laminates ... 10Chapter 4 Decks ... 14
4.1 General ... 14 4.2 Minimum Thickness of Deck Laminates ... 14 4.3 Local Compensation of Decks ... 15Chapter 5 Frames ... 17
5.1 General ... 17 5.2 Construction ... 175.3 Spacing of Frames ... 17 5.4 Transverse System ... 17 5.5 Longitudinal System ... 18 5.6 Hat-type Construction ... 19
Chapter 6 Bottom Construction ... 20
6.1 General ... 20 6.2 Center Girders ... 20 6.3 Side Girders ... 21 6.4 Transverse System ... 21 6.5 Longitudinal System ... 22 6.6 Double Bottoms ... 22 6.7 Forward Strengthened Bottom ... 24 6.8 Hat-Type Construction ... 24Chapter 7 Under Deck Construction ... 26
7.1 General ... 26 7.2 Spacing ... 26 7.3 Transverse System ... 26 7.4 Longitudinal System ... 27 7.5 Hat-Type Construction ... 28 7.6 Pillars ... 28Chapter 8 Watertight Bulkheads ... 30
8.1 Arrangements ... 30 8.2 Construction of Watertight Bulkheads ... 30Chapter 9 Deep Tanks ... 33
9.1 General ... 33 9.2 Bulkhead Laminates... 33 9.3 Additional Requirements ... 34Chapter 10 Machinery Spaces ... 36
10.1 General ... 36 10.2 Construction under Main Engines ... 36 10.3 Auxiliary Machinery Foundations ... 36Chapter 11 Superstructures and Deckhouses ... 37
11.1 General ... 37 11.2 Construction ... 37 11.3 Windows ... 38Chapter 12 Hatchway Openings, Machinery Openings and Other Deck Openings ... 40
12.1 General ... 40 12.2 Hatchway Openings ... 40 12.3 Machinery Openings ... 42 12.4 Other Openings ... 42-1-
II.1
Chapter 1 Shell Laminates
1.1 Construction and Arrangement
1.1.1 The requirements in this Part apply to ship‘s hull of a single skin construction consisting FRP shell and deck laminates stiffened by a system of supporting members, or of a sandwich construction consisting FRP laminate on either side of a core material which is assumed to be efficient bonded between skins and core that when a sandwich panel is exposed to a lateral load the bending moments are carried by the skins and the shear forces by the core.
1.1.2 In single skin construction, hull laminates are generally supported by primary members in a collective term of girder. Stiffener is a collective term for secondary supporting members. Other terms concerned are:
(a) Floor - bottom transverse girder
(b) Web frame and / web beam - side and deck transverse girder (c) Stringer - side shell or bulkhead horizontal girder
(d) Vertical web - bulkhead girder (e) Beam - deck stiffener
(f) Frame - side stiffener
(g) Longitudinal - bottom, side and deck stiffener (h) Transverse - bottom transverse stiffener
1.1.3 Bottom and deck are normally to be longitudinally stiffened while the side shell may be longitudinally or vertically stiffened. The longitudinal stiffeners are to be preferably continuous through transverse members and supported by bulkhead and/or web frames. Ends of longitudinals are to be fitted with brackets or to be tapered out beyond the point of support.
1.1.4 Sufficient transverse strength is to be provided by means of transverse bulkheads or girder structures. Web frames are to be continuous around a cross section . i.e. floor, web frame and web beam are to be efficiently connected. Longitudinal girders supporting the bottom panels and for docking purposes are to be carried continuously through bulkheads. Engine girder and floor in way of thrust bearings are to be additionally provided with suitable local reinforcements.
1.1.5 Structural continuity of the primary supporting members is to be maintained by fitting rounded brackets at the conjunctions or tapered to zero at their ends. In superstructures and deckhouses, the exposed and internal bulkheads are to be in line with bulkheads in the hull or effectively supported by girders, frame or pillars. The transition at the break of superstructure is to be smooth without local discontinuities. Openings for doors and windows are to have rounded corners and substantially strengthened along the edge.
1.2 Scantlings
1.2.1 The scantling required in the Rules are specified on the basis of the plastics, reinforced by chopped mats and woven rovings, of which the mechanical properties excluding gel coat are to be in compliance with the followings:
(a) Tensile strength 110 N/mm2
(b) Modulus of tensile elasticity 7000 N/mm2 (c) Bending strength 160 N/mm2
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II.1
(d) Modulus of bending elasticity 7200 N/mm2
1.2.2 The scantlings required may be modified as specified in the following, in case of a single skin construction moulded by the FRP having the strength higher than those specified in 1.2.1.
(a) Thickness requirements may be multiplied by a factor obtained from the following formula:
(160/B)1/2 where:
B = Bending strength of the laminate obtained form the strength tests specified in 2.6 of Part I , in N/mm2 (b) Requirements of section modulus can be multiplied by a factor obtained from the following formula:
110/T where:
T = Tensile strength of the laminate obtained form the strength tests specified in 2.6 of Part I , in N/mm2 1.2.3 The section modulus of the structure members required in the Rules are for those sections including effective breadth on the laminate by 150 mm either side of the web.
1.2.4 In addition to the requirement of section modulus, stiffeners of hat-type construction either moulded to a hollow form or moulded covering cores are to be of suitable proportions.
(a) The widths and heights of the stiffeners are not to be greater than the value obtained from the following formula:
Width of crown : 20 tc K mm Height of webs : 30 t K mm where:
tc = Thickness of crown, in mm
t = Thickness of webs and flanges, in mm K = 1 and may be taken as (Zr/Za)1/2 where:
Zr = Required section modulus for the stiffener, in cm3 Za = Actual section modulus of the stiffener, in cm3
(b) Where laminates forming hat-type stiffeners are bonded to the skin with flanges, the minimum lap of joint is to be 0.2 height of the stiffener but not less than 50 mm and need not to be greater than 6t.
(c) The core for moulding of stiffeners may be reckoned in the strength at the discretion of the Society.
1.2.5 In design of a sandwich construction, the scantlings of inner and outer skin of FRP laminates are to be
1.2.5 In design of a sandwich construction, the scantlings of inner and outer skin of FRP laminates are to be