Section 2 Laminating and Moulding

201. General

1. Moulding of FRP is to be carried out under the supervision of a well-experienced technical expert.

2. Mouldings which are deemed not to have been fully cured are not to be kept under the environ- mental condition which may prevent them from effective curing. And, post curing of moulding at high temperature, if intended, is to be approved by the Society.

202. Moulding

1. Mould

(1) Moulds are to be reinforced properly with proper material and of sufficient strength to maintain their shape and fairness of moulding.

(2) Moulds are not to give harmful influence to laminates. The surface smoothness of moulding

works is to comply with discussions between manufacturer and ship owners.

(3) Where multiple section moulds are used, the sections are to be carefully aligned prior to moulding. Mismatch between mould sections is to be eliminated.

(4) Mouldings are to be cleaned, dried and in place so that they stabilize at the workshop temper- ature before the releaser is applied.

(5) Where metallic moulds are used, welding is to be minimised to avoid distortion of panels.

(6) Prior to use all moulds are to be conditioned to the workshop temperature.

2. Moulding

(1) Before moulding, examinations are to be made in detail with respect to the items listed in the following and moulding is to be proceeded on the basis of such examinations.

(A) Environmental conditions of laminating shops, controlling system thereof and curing time of

resins

(B) Operation procedure and scheduled operation process

(C) Kinds, cutting methods, overlap of joints, edge preparation and number of plies of fibre re-

inforcements

(D) Kinds, amount, blending quantity at one time and blending procedures of resins used.

(2) It is recommended that the structural members are moulding in one body with the prescribed hull laminates before they advance in cure. However, structural members separately moulding may be bonded to the hull laminates.

203.

Releaser

1. Proper releaser are to be coated evenly on the working surface of moulding. However, releaser containing silicon is not to be used.

2. The releaser is to be compatible with the mould surface, the resins applied in the laminating proc- ess and with moulding release films used previously.

204. Gelcoat

1. Gelcoat resins are to be evenly coated or sprayed.

2. The standard thickness of gelcoat film is approximately 0.5.

205. Lamination

1. General

(1) Grade 1 polyester is to be used for the hull shell laminate in single skin construction and for the outer hull skin laminate in sandwich construction.

(2) Framing and stiffening sections are to be built up layer by layer in accordance with an ap-

proved procedure, particular attention being given to ensure a satisfactory bond and structural continuity at the ends and intersections.

(3) Discontinuities and hard points in the structure are to be avoided, and where the strength of a

stiffening member is impaired by any attachment of fittings, openings, drainage arrangements, etc., compensation is to be provided.

(4) The outer reinforcement ply of the outer hull skin laminate is to be at least 450 gÕmĪ of chop- ped strand fibres containing as little water soluble bonding components as possible. Normally spray roving or powder bound mat should be used. Alternatively a 300 gÕmĪ mat and a light

surface mat can be used. Other material systems giving an equivalent surface protection may al- so be accepted.

(5) Areas inside the hull expected to be continuously exposed to water submersion (i. e. bilge wells etc.) and the inside of tanks shall have a surface lining consisting of at least 600 gÕmĪ re- inforcement material.

(6) The time interval between applications of each layer of reinforcement is to be within the limits specified by the FRP material supplier. For thicker laminates care is to be taken to ensure a time interval sufficiently large to avoid excessive heat generation.

(7) When laminating is interrupted, and where other than an epoxy resin system is being used, the first of any subsequent layers of reinforcement to be laid in that area is to be of chopped glass fibre or other type of material to enhance the interlaminar strength properties of the laminate.

(8) Curing systems are to be selected with due regard to the reactivity of the polyester and in ac- cordance with the supplier's directions. Heat development during curing is to be kept at a safe level. The quantity of curing agents is to be kept within the limits specified by the supplier.

(9) The cut edges of laminates, holes for bolts, etc. are to be thoroughly covered with resin so that the fibre reinforcements are not exposed.

(10) The bonding and fastening are to be in accordance with the requirements of Sec 6.

2. Laminating plans

(1) FRP ships' builders should submit details of laminating plans and they are to be approved prior to constructions

(2) The laminate schedule is to clearly define the logical sequence of production and is to identify the

specific materials to be used. The materials used for constructions and fastening are not to disturb curing of resins.

(3) The kind, thickness, composition thickness and laminating weight of gelcoats, chopped mats and core are indicated in the laminating plans.

(4) The extents of each reinforcement should be defined and details related in overlap, staggering thicknesses and reinforcement's cutting should be prescribed in the laminating plans .

(5) The submitted plans are to clearly define the laminate sequence at corner joints. In general, cor- ner laminates are to be boxed and all cuts are to be alternately staggered to avoid a fault line. At corner joints vertical and horizontal laminates are to be laid alternately and butts are to be

staggered accordingly.

(6) Changes in laminate thickness are to be made using a gradual taper. The length of such taper

is, in general, not to be less than 100 mm.

206. Release and curing

1. After completion of the lay-up, the moulding is to be left in the mould for a period to allow the resin to cure before being removed. This period can vary with ambient temperature, the type of

resin and the complexity of the moulding, but is to be not less than

mended by the resin manufacturer.

2. Care is to be exercised during removal from the mould to ensure that

12 hours or that recom-

the hull, deck and other

large assemblies are adequately braced and supported to avoid damage to and maintain the form of the moulding.

3. Where female moulds are adopted, all primary stiffening and transverse stalled prior to removal from the mould unless agreed otherwise.

bulkheads are to be in-

4. Mouldings are, in general, to be stabilised in the moulding environment for at least 24 hours, or that recommended by the resin manufacturer before the application of any special cure treatment, details of which are to be submitted for approval.

5. Removal from the mould is not to be attempted until a minimum Barcol reading recommended by the resin manufacturer or a value of 20 has been attained. Subsequently, the moulding is not to be moved outside of the controlled environment until a minimum Barcol reading recommended by the resin manufacturer of 35 (or equivalent) has been recorded

207 Repair

1. Minor repairs are to be agreed with the attending Surveyor prior to being carried out. The Builder is to incorporate details of the agreed repair procedures in the quality control system.

2. Structural repairs are subject to individual consideration and full written details must be approved by the plan approval teams prior to introduction.

208. Sanding

Where the outer surface of FRP laminates is sanded, attention is to be paid lest the fibre reinforce- ments on the sanded surface should be heavily damaged.