Section 2 Materials

2.1.1 The Rules are applicable to craft generally constructed of fibre reinforced plastic (typically with unsaturated polyester resin), using hand lay-up, mechanical deposition, contact moulding techniques or vacuum assisted techniques. Construction may be either single-skin or sandwich construction, or a combination of both.

2.1.2 Other materials (i.e. non-FRP materials) are to be of good quality, suitable for the purpose intended and, where applicable, are to comply with LR's requirements appropriate to the material. Details of these materials are to be stated on the relevant construction plans. Where these materials are attached to, or encapsulated within, the plastics construction, the material is not to affect adversely the cure of the plastics materials.

2.1.3 Where moulding techniques and methods of construction differing from those given in Pt 8, Ch 2, 3 General construction process are proposed, details are to be submitted for consideration by LR.

2.2.1 The resins used are to be of a type that has been approved by LR for marine construction purposes. Samples of the resin batches being used in the construction may be taken for limited quality control examination at the discretion of the Surveyor, see Ch 14, 5 Control of material quality for composite constructionof the Rules for Materials .

2.2.2 The cure procedure for the resin system is to be that recommended by the resin manufacturer for the particular application, so that the resin will cure in the required time, in accordance with the approved cure schedule.

2.2.3 Wax additives are only to be added by the resin manufacturer in accordance with the agreed procedure and tested accordingly. The base resin is to be of an approved type.

2.2.4 Where a resin contains an ingredient that can settle within the resin system, it is the Builder's responsibility to ensure that the resin manufacturer's recommendations regarding mixing and conditioning are complied with prior to use.

2.3.1 Compliant resins for structural applications are to be of types accepted by LR, see Ch 14, 2.15 Adhesive and sealant materials, and are to be used strictly in accordance with the manufacturer's recommendations.

2.3.2 Details of the compliant resin to be used in the construction are to be included on the Material Data Sheet at the initial stages of plan approval. The plans submitted for approval are to identify which compliant resins are used in different applications. Surface preparations and over— bonding are also to be identified on the submitted plans.

2.3.3 Proposals for the use of structural filleting applications using compliant resin are to be submitted in detail. Such proposals will be subject to individual consideration.

2.3.4 The acceptance of the use of structural fillets of compliant resins in place of boundary bonding angle laminates required by Pt 8, Ch 3, 1.19 Boundary bonding, will be subject to the designer/Builder providing the necessary information and test results to demonstrate equivalence with the Rule requirement for boundary bonding angle laminates.

2.3.5 Air inclusions that may affect the structural efficiency of the joint are to be avoided.

2.4.1 Bulk storage of resin is to be arranged in accordance with the resin manufacturer's recommendations in suitably adapted and insulated tanks. Tanks and pipes are to be periodically flushed in accordance with the resin manufacturer's recommendations. A ready use store is to be provided where appropriate.

2.5.1 Gel coats based on orthophthalic polyester resin systems are not acceptable. All gel coats are to be used strictly in accordance with the manufacturer's recommendations. The curing system is to be in accordance with Pt 8, Ch 2, 2.2 Resin system 2.2.2.

2.5.2 Where pigments are to be added reference is to be made to Pt 8, Ch 2, 2.6 Curing systems. Where pigments are added by the Builder, the gel coat is to be allowed to stand for sufficient time to permit entrapped air to be released. The method of mixing is to be carried out strictly in accordance with the resin and pigment manufacturer's instructions.

2.5.3 Where the temperature of the gel coat resin is below that of the workshop, the gel coat resin is to be conditioned to attain the workshop temperature prior to use.

2.5.4 Where the inspection of the mould is an agreed hold point, required by the quality plan, the mould is to be inspected by the attending Surveyor prior to gel coating. The Surveyor may also require to witness the initial application of the gel coat, see also Pt 8, Ch 2, 3.3 Laminating.

2.5.5 Where a gel coat is not used, details of the proposed water barrier are to be submitted for consideration.

2.5.6 Where a painted finish is to be adopted in place of a gel coat a suitable tie coat may be required in accordance with the paint manufacturer's recommendations.

2.5.7 Where the hull is of sandwich construction built on a male plug mould, the water barrier on the outer surface of the hull will be specially considered.

2.6.1 Curing systems are to be in accordance with Pt 8, Ch 2, 2.2 Resin system 2.2.2 and are to be fully compatible with the resins and reinforcements to be used.

2.6.2 For polyester and vinylester resins the level of catalyst and accelerator are to be as recommended by the manufacturer to ensure full polymerisation of the resin. In general, the rate of gelation is to be controlled by the amount of accelerator added to the resin. The amount of catalyst is not to be less than one per cent, by weight, of the base resin.

2.7.1 The gelation time is to be suitable for the proposed application such that full wet-out of the reinforcement can be obtained without unnecessary drainage on vertical surfaces or excessive loss of the monomer.

2.7.2 The gelation time quoted on the Material Data Sheet is to be the typical gelation time for a laminate as laid in the mould, i.e. the working life of the resin.

2.7.3 The gelation time may need to be varied to suit changing ambient workshop temperatures. For polyester and vinylester resins this is, in general, to be adjusted by variation of the accelerator and not by variation of the catalyst.

2.7.4 All resins are to be mixed in accordance with the resin manufacturer's recommendations.

2.8.1 The types of pigment used are to be such that the final cure of the resin is not affected.

2.8.2 The pigment may be added to the resin by either the resin manufacturer or the moulder, and when added by the moulder it is to be as a paste dispersal in the same or compatible resin. Pre-pigmented gel coats are recommended. Where pigments are added by the Builder thorough mixing is essential to avoid striations. See also Pt 8, Ch 2, 2.2 Resin system 2.2.4 and Pt 8, Ch 2, 2.3 Compliant resins 2.3.2.

2.8.3 The amount and type of pigment added is not to exceed that recommended by the resin manufacturer for a satisfactory depth of colour. Proposals to use amounts of pigment solids in excess of five per cent, by weight of the base resin, will be subject to individual approval and testing.

2.8.4 It is recommended that pigments are not to be added to the gel coat or laminating resins used in the underwater portion of the hull laminate or in laminates forming the boundaries of fuel oil and water tanks.

2.8.5 The addition of pigments is not to unduly affect the gelation time of the resin system or the physical properties of the gel coat layer of the laminate produced. The resin and/or pigment manufacturer's written confirmation in this respect is to be obtained and recorded in the Builder's quality control documentation.

2.8.6 The aesthetic appearance of mouldings is strictly a matter between the moulder and the Owner.

2.9.1 All fillers added by a Builder are to be of the dispersed type. The amount of filler that may be added to an approved resin is to be that recommended by the resin manufacturer and is not to alter significantly the viscosity of the resin nor is it to affect the overall strength properties of the laminate. Recommendations by the resin manufacturer to adopt amounts of fillers in excess of 13 per cent by weight of the base resin will be subject to individual approval and testing.

2.9.2 Pigments, thixotropes and fire retardant additives are to be considered as fillers in the calculation of total filler content.

2.9.3 Fillers are to be carefully and thoroughly mixed into the base resin that is then to be allowed to stand to ensure that entrapped air is released. The resin manufacturer's recommendations regarding the method of mixing are to be followed.

2.9.4 Fillers are not to be used in the structural laminates forming the boundaries of fuel oil and water tanks.

2.9.5 Details of all fillers and fire retardant additives are to be included on the Material Data Sheet at the initial stages of plan appraisal.

2.9.6 The amount of fire retardant additives may be in excess of that indicated in Pt 8, Ch 2, 2.9 Fillers 2.9.1 provided that due account is taken of the reduced mechanical properties when determining scantlings in accordance with the Rules.

2.10.1 The attention of Owners and Builders is drawn to the additional statutory regulations regarding fire safety that may be imposed by the National Authority of the country in which the craft is to be registered or the Governments of the states to be visited.

2.10.2 For requirements regarding fire safety, see Pt 17 Fire Protection, Detection and Extinction.

2.10.3 Where laminates are required to have fire retardant or restricting properties, details of the proposals are to be submitted for approval. Where additives to the resin system are used, the type and quantity are to be as recommended by the resin manufacturer. Test results of independently tested fire retardant and fire restricting materials are to be submitted for design purposes.

2.10.4 All fire retardant resin systems are to be used strictly in accordance with the resin manufacturer's recommendations.

2.10.5 The use of fire retardant and fire restricting materials in craft required to comply with statutory requirements will be subject to the individual approval of the National Authority of the country in which the craft is to be registered, or LR where authorised to undertake this work on behalf of the National Authority.

2.11.1 All fibre reinforcements are to be of a type approved by LR.

2.11.2 All reinforcements are to be stored strictly in accordance with the manufacturer's recommendations. Rolls of reinforcement are to remain in their original packaging to minimise contamination. The quality control documentation is to provide traceability of all reinforcements using the manufacturer's batch numbers.

2.11.3 The materials are to be free from imperfections, discolouration, foreign matter and other defects.

2.11.4 Pre-impregnated reinforcements are to be suitably stored in an approved area. Detailed storage records are to be maintained as part of the quality control documentation.

2.12.1 Lightweight surfacing materials for reinforcing resin rich surfaces are to be compatible with the resin being used. Details of the materials and the fibre contents, by weight, are to be included on the Materials Data Sheet (Form 2075).

2.12.2 Where peel ply materials are to be used, the finish is to be such that, after removal, it does not interfere with any subsequent bonding processes.

2.13.1 Core materials for sandwich construction are to be approved by LR, see Ch 14, 2 Tests on polymers, resins, reinforcements and associated materials.

2.13.2 All core materials are to be used in accordance with the manufacturer's application procedure, a copy of which is to be submitted for information, with the relevant construction plans of the craft. A second copy is to be incorporated into the quality control documentation.

2.13.3 Rigid expanded foam plastics are to:

1. be of closed-cell types and impervious to water, fuel and oils;

2. have good ageing stability;

3. be compatible with the resin system;

4. have good strength retention at 60°C;

5. have characteristics and mechanical properties of not less than those indicated in Ch 14, 5.12 Closed cell foams for core construction based on PVC or polyurethane 5.12.1 of the Rules for the Manufacture, Testing and Certification of Materials, July 2022; and

6. if manufactured into formable sheets of small blocks, the open weave backing material and adhesive are to be compatible and soluble, respectively, with the laminating resin.

2.13.4 Balsa wood is to:

1. be end grained;

2. have been chemically treated against fungal and insect attack and kiln dried shortly after felling;

3. have been sterilised;

4. have been homogenised;

5. have an average moisture content of 12 per cent;

6. have characteristics and mechanical properties of not less than those indicated in Table 2.2.1 Minimum characteristics and mechanical properties of end-grain balsa; and

7. if manufactured into formable sheets of small blocks, the open weave backing material and adhesive are to be compatible and soluble, respectively, with the laminating resin.

2.13.5 Where necessary, foam core materials are to be conditioned in accordance with the manufacturer's recommendations. Conditioning at an elevated temperature, in excess of that which may be experienced in service, may be necessary to ensure the release of any entrapped residual gaseous blowing agents from the cells of the foam core.

2.13.6 Synthetic `felt' type core materials are to be approved in accordance with Ch 14, 2.10 Synthetic felt type materials with or without microspheres of the Rules for Materials.

2.13.7 Other types of core materials will be individually considered, on the basis of these Rules in relation to their characteristics and intended application.

2.13.8 Balsa wood is to remain in protective packaging until required in production. Part packages are to be sealed to prevent the ingress of moisture.

2.14.1 Core bonding materials for structural applications are to be of types accepted by LR, and are to be used strictly in accordance with the manufacturer's instructions.

2.14.2 Details of the proposed core bonding paste to be used with the core material are to be indicated on the Materials Data Sheet and the appropriate construction plans.

2.14.3 The Builder is to demonstrate that a uniform thickness of bonding paste is obtained by use of notched trowels or comb gauges. For the use of bonding pastes, see Pt 8, Ch 2, 4.2 Laminating 4.2.7.

2.15.1 Adhesives for structural applications are to be of types accepted by LR, see Ch 14, 2.15 Adhesive and sealant materialsof the Rules for Materials, and are to be used strictly in accordance with the manufacturer's recommendations.

2.15.2 The details of all structural adhesives are to be specified on the Materials Data Sheet and on the relevant construction plans submitted.

2.15.3 Details concerning the handling, mixing and application of adhesives are to form part of the Builder's production plan.

2.15.4 Particular attention is to be given to the surface preparation and cleanliness of the surfaces to be bonded.

2.15.5 Where excessive unevenness of the faying surfaces exists a suitable gap filling adhesive is to be used or local undulations removed by the application of additional reinforcements.

2.15.6 The Builder's quality plan is to identify the level of training required for personnel involved in the application of structural adhesives.

2.16.1 Metallic materials (such as suitable marine grades of stainless steel or aluminium alloys) used in the construction are to comply with the requirements of Pt 8, Ch 2, 2.1 General 2.1.2. Where structural members or components manufactured from these, or other materials, are to be encapsulated within or structurally bonded to laminates, the material is not to adversely affect the cure of the resin system. The surface area of the component that will be in contact with the resin is to be thoroughly cleaned, degreased and, where practicable, either shot blasted or abraded to provide a key.

2.16.2 Where metallic sections are to be bolted into a structure, the bolting requirements are to be determined by direct calculations that are to be submitted for consideration. Appropriate precautions against corrosion are to be taken.

2.16.3 Where plywood and timber members are to be used in structural applications and are to be laminated onto, or encapsulated within the laminate, the surface of the wood is to be suitably prepared and primed prior to laminating.

2.17.1 Plywood, for structural applications, is to be of a high quality marine grade material approved by LR, see Ch 14, 2.14 Plywoods. In general, the plywood is to be manufactured to a high standard of finish in accordance with ISO or other Recognised Standards and is to meet, or be equivalent to, the following general requirements:

1. Have good quality face and core veneers of a durable hardwood species.

2. The number of veneers is to be in accordance with Table 2.2.2 Number of veneers.

3. The veneers are to be bonded with a WBP (water and boil proof) type adhesive.

4. Have a moisture content not exceeding 15 per cent.

2.17.2 Butts and seams are to be scarfed or butt strapped where necessary. The length of the scarf is to be not less than eight times the plywood thickness. The scarf is to be glued and, if made in situ, fitted with a backing strap of width not less than 10 times the panel thickness. The strap is to be glued and fastened with two rows of fastenings of the size given in Table 2.2.3 Butt strap fastenings and spaced at approximately eight times the panel thickness.

2.17.3 Butt straps are to be of the width given in Table 2.2.3 Butt strap fastenings and the same thickness as the panel. The strap is to be glued and double/treble fastened to the panel. Sizes of fastenings are given in Table 2.2.3 Butt strap fastenings.

2.17.4 For further information regarding plywood see Pt 8, Ch 3, 1.21 Plywood.

2.18.1 The acceptance of timber in the construction will be subject to individual consideration depending upon the intended use and timber involved.

2.18.2 The timber is to be of good quality and properly seasoned. Timber is to be free from heart, sapwood, decay, insect attack, splits, shakes and other imperfections that would adversely affect the efficiency of the material. It is also to be generally free from knots, although an occasional sound intergrown knot would be acceptable.

2.18.3 The moisture content of timber for bonded or overlaminated applications using polyester or epoxy resins is, in general, to be nominally 15 per cent. Contents slightly greater than this value are recommended when resorcinol glues are used, and contents slightly lower than this value are required when phenolic or urea-formaldehyde resins are used.

2.18.4 For further information regarding timber see Pt 8, Ch 3, 1.20 Timber.

2.19.1 Release agents are to have no inhibiting effect on the gel coat resin and are to be those recommended by the resin manufacturer.