Section 10 Masts and standing rigging

10.1.1 Masts are generally to be of tubular construction and may be either stayed or unstayed. Special consideration will be given to other forms of construction.

10.1.2 Masts are to be of sufficient strength to withstand the worst combination of loads from both the operational case with full sail, reduced sail configurations where applicable and survival conditions.

10.1.3 Masts are to be adequately supported using stays if necessary.

10.1.4 Drainage is to be provided to prevent the build-up of sea-water or condensation within the mast structure. Steel masts should, where possible, be coated internally with a suitable anti-corrosive preparation.

10.1.5 Openings in the masts for entry and exit of running rigging or cables should be adequately compensated with suitable insert plates or doublers.

10.1.6 Masts are to be efficiently integrated into the hull and in principle, carried through to the keel. Alternative arrangements of supporting masts will require to be specially considered.

10.1.7 Where ship response data are not available the values for roll, pitch and heave given in Table 2.10.1 Ship motions should be used.

10.2.1 The mast and standing rigging design is to be considered with respect to the loads from the following conditions:

Table 2.10.1 Ship motions

Motion	Maximum single amplitude	Period, in seconds
Roll	Φ = sin–1θ degrees but need not exceed 30° and is not to be taken less than 22°
Pitch	Ψ = 12e –0,0033Lpp degrees, but need not exceed 8°
Heave
where L pp, B as defined in Pt 3, Ch 1, 6 Definitions GM = transverse metacentric height of loaded ship, in metres θ =

10.2.2 The mast section is to be designed to have a margin against failure due to column buckling using the greatest combined design axial and bending stress in both the transverse and fore and aft directions.

10.2.3 For loadcases R1 and R2 described in Pt 4, Ch 2, 10.2 Design loadings and allowable stresses 10.2.1, the following condition is to be satisfied:

For loadcase R3 the following condition is to be satisfied:

10.2.4 For thin walled masts, constructed from either flat or curved shells, calculations are to be submitted demonstrating adequate margin against local elastic instability.

10.3.1 In general masts are to be constructed from either steel or aluminium alloy tubular members, extrusions and/or welded constructions, and are, generally, to comply with LR's Rules for the Manufacture, Testing and Certification of Materials, July 2019, incorporating Notice No. 1 & 2 , where appropriate.

10.3.2 Other materials will be specially considered.

10.4.1 Standing rigging is to be so arranged such that it does not foul running rigging or interfere with the operation of the sails. Protection is to be provided against routine quay contacts.

10.4.2 Standing rigging is to be effectively attached to the masts, deck and hull structure and is to be so designed that it cannot become disconnected during operation.

10.4.3 Standing rigging is to be properly erected using tensioning devices to ensure that the correct pre-tension is applied as specified by the designer.

10.4.4 The initial pre-tension applied to standing rigging is to be measured and recorded.

10.5.1 The forces in the standing rigging are to be obtained by direct calculation methods for the load conditions given in Pt 4, Ch 2, 10.2 Design loadings and allowable stresses 10.2.1.

10.5.2 The minimum factors of safety on the breaking strength of shrouds and stays are as follows:

10.6.1 Standing rigging is to be effectively attached to the masts, ship's deck or bulwark structure. Chain plates, mast eyeplates and the structure in way are to be reinforced to withstand a load of 1,2 x breaking strength of the appropriate shroud or stay.

Generally the hull structure in way of shroud/stay attachment should be capable of withstanding the wire breaking load without permanent deformation of the structure.

10.6.2 Increased mast wall thickness, or internal or external mast stiffening rings or diaphragms are to be arranged in way of the toes of shroud and stay eyeplates to resist mast wall punching shear loads. Where additional mast stiffening rings or diaphragms are not fitted, the mast wall is not to be less than:

where

h eye	=	eyeplate pin axis from mast wall, mm, see Figure 2.10.1 Definition of h eye and l eye
B s	=	breaking strength, in kN, of attached rigging component
k mast	=	mast material factor, k
t eye	=	eyeplate thickness, mm, see Figure 2.10.1 Definition of h eye and l eye
eye	=	eyeplate length, mm, see Figure 2.10.1 Definition of h eye and l eye

10.6.3 The attachments of the stays and shrouds are to be efficiently integrated into the hull structure and due regard given to any attachments to the sheerstrake.

Figure 2.10.1 Definition of h _eye and l _eye

10.6.4 Where it is intended to use mechanical attachments (bolting) of running rigging or other gear to the mast walls, the number of holes are to be kept to a minimum and are to be staggered in order to maintain the structural integrity of the mast. All details are to be submitted.

10.7.1 In general, standing rigging is to be made from galvanised steel wire rope (GSWR) with galvanised steel rigging screws, shackles and terminations, and is to comply with the requirements of LR. Special consideration will, however, be given to other rigging materials.

10.7.2 Alternatively, stainless steel wire rope or solid rod rigging may be used in place of GSWR.

10.7.3 The steel wire rope, solid rods and loose fittings used for standing rigging are to be manufactured to a recognised National or International Standard and at an LR approved works.

10.7.4 Rigging components from other sources will be specially considered.

10.7.5 Where stainless steel rigging is employed, particular attention is to be given to the selection of the grade of material used as some stainless steels are prone to stress corrosion cracking and consequent fatigue failure, the onset of which is not readily observed.

10.7.6 Attention is drawn to the requirements of the Flag Administration for the vessel who may have requirements regarding the application of certain materials, systems or criteria.

10.8.1 All equipment items used for standing rigging, including loose items of gear such as shackles, bottle screws, sheaves, etc. are to be tested and surveyed in accordance with LR requirements. For systems employing specialised devices or materials, individual consideration will be given to the testing and survey requirements.

10.8.2 For sailing passenger ships, the equipment requirement will be in accordance with the letter and numeral two grades higher than that corresponding to the calculated Equipment Numeral.