Section 2 Minimum thickness requirements

2.1.1 Structural laminates, used for both single skin and sandwich construction are, in general, to incorporate not less than 40 per cent, by weight, of woven or cross-ply reinforcement.

2.2.1 The minimum thicknesses of single skin laminates are as indicated in the appropriate Sections.

2.3.1 The minimum amount of reinforcement in single skin laminates which form the inner and outer skins of sandwich panels are as indicated in Pt 8, Ch 3, 2.5 Minimum skin reinforcement in sandwich laminates 2.5.1. Where the structural requirements for thickness of either the bottom shell outer skin, or inner skin in way of an integral tank, is less than that required by Pt 8, Ch 3, 2.5 Minimum skin reinforcement in sandwich laminates 2.5.1, a 20 per cent reduction in the minimum amount of reinforcement will be acceptable, conditional upon a vacuum test to demonstrate the watertight integrity and also an impact test for impact resistance of the laminate, see Pt 8, Ch 3, 2.9 Sheathing 2.9.2.

2.4.1 The Rule minimum skin thicknesses for single skin laminates as determined from the appropriate Sections of the Rules are to be corrected for craft type irrespective of the reinforcement being used, the corrected minimum skin thickness of side, bottom, transom, wet-deck, vehicle deck and weather decks is to be determined from:

Single skin laminates:

2.4.2 All minimum thicknesses of laminate for both stiffener and single skin laminate components are based on an assumed fibre content, f _c, of 0,5. Where the fibre content by weight, f _c, is less than 0,5 the required minimum thicknesses are to be determined from:

2.4.3 The equation in Pt 8, Ch 3, 2.4 Laminate thickness of single skin laminates 2.4.2 relates to polyester 'E' glass laminates. Other laminates will be considered on an equivalence basis.

2.5.3 The Rule minimum amount of reinforcement in Pt 8, Ch 3, 2.5 Minimum skin reinforcement in sandwich laminates 2.5.1 is to be corrected for craft length, irrespective of the reinforcement being used; the craft length correction factor is to be determined from:

2.5.4 The minimum amount of reinforcement is based on an assumed fibre content, f _c, of 0,5. Where the fibre content by weight, f _c, is greater than 0,5, the fibre volume correction factor is to be determined from:

2.5.5 In areas where impact loads are not likely to occur, special consideration will be given to laminates with amount of reinforcement less than that required by Pt 8, Ch 3, 2.5 Minimum skin reinforcement in sandwich laminates 2.5.1, provided that all of the structural strength requirements of the Rules are complied with.

2.6.1 The minimum thickness of laminate for all stiffening members passing through, or forming the boundary of integral fuel oil and water tanks is to be not less than 4,5 mm irrespective of fibre content.

2.6.2 Where the boundaries of integral fuel oil and water tanks are of sandwich skin construction the minimum amount of reinforcement in the laminate providing the fluid barrier, without satisfactory material testing, is to comply with the requirements of Pt 8, Ch 3, 2.5 Minimum skin reinforcement in sandwich laminates 2.5.1, see Pt 8, Ch 3, 2.3 Sandwich skin laminate 2.3.1.

2.6.3 Where the boundaries of integral fuel oil and water tanks are of single skin construction, in no case is the tank laminate thickness, determined in accordance with Pt 8, Ch 3, 7.4 Deep tanks, to be less than 5,0 mm irrespective of fibre content.

2.7.1 Where the Rules do not specifically define the requirements for novel features, the scantlings and arrangements are to be determined by direct calculations. Such calculations are to be carried out on the basis of the Rules, Recognised Standards and good practice, and are to be submitted with the relevant construction plans for appraisal, see also Pt 8, Ch 1, 2.6 Novel features.

2.8.1 Due consideration is to be given to the scantlings of all structures which may be subject to local impact loadings. Impact tests may be required to be carried out at the discretion of LR to demonstrate the suitability of the proposed scantlings for a particular application.

2.8.2 The minimum skin thickness requirements may, subject to the agreement of LR, be reduced provided that suitable impact tests are carried out to demonstrate that the proposed laminates have not less than the equivalent impact resistance to that of a laminate which satisfies the Rule minimum thickness. In addition it is assumed that this reduced laminate satisfies the structural strength and deflection requirements of the Rules.

2.9.1 Areas of shell and deck which are subject to additional wear by abrasion e.g. passenger routes, working areas of fishing craft, forefoot region, etc, are to be suitably protected by local reinforcement as given in Pt 8, Ch 3, 3.14 Local reinforcement or sheathing. This sheathing may be of timber, rubber, steel, additional layers of reinforcement, etc. as appropriate. Details of such sheathing and the method of attachment are to be indicated on the relevant construction plans submitted for appraisal.

2.9.2 The attachment of sheathing by mechanical means such as bolting or other methods is not to impair the structural integrity of the laminate or the watertight integrity of the craft. Through bolting of the hull is to be kept to a minimum and avoided where practicable. The design arrangements in way of any through bolting is to be such that damage to the sheathing will not impair the watertight integrity of the attachment to the hull.