Section 7 Machinery requirements for first-year ice conditions – Ice Classes 1AS FS(+), IAS FS, 1A FS, 1A FS(+), 1B FS, 1B FS(+), 1C FS(+) and 1C FS

7.1.1 In addition to the requirements of the Finnish- Swedish Ice Class Rules, the following Sections are to be complied with for Ice Class 1AS FS, Ice Class 1A FS, Ice Class 1B FS and Ice Class 1C FS, where applicable. Alternative arrangements to attain similar performance will be specially considered.

7.2.1 If the propeller is not fully submerged when the ship is in ballast condition, the requirements for Ice Class 1A FS is to be used for Ice Class 1B FS and Ice Class 1C FS.

7.3.1 Where the blade thickness derived from the Finnish-Swedish Ice Class Rules is less than the blade thickness derived by Pt 5, Ch 7, 3.1 Minimum blade thickness, the latter is to apply.

7.4.1 The thickness of other sections is to conform to a smooth curve connecting the section thicknesses as determined by the Finnish-Swedish Ice Class Rules.

7.5.1 The thickness of blade edges is to be not less than 50 per cent of the derived tip thickness, t, measured at 1,25t from edge. For controllable pitch propellers, this applies only to the leading edge.

7.6.1 The strength of mechanisms in the boss of a controllable pitch propeller is to be 1,5 times that of the blade when a load is applied at the radius 0,9D/2 in the weakest direction of the blade.

7.7.1 When it is proposed to use keyless propellers, the fit of the propeller boss to the screwshaft will be specially considered.

7.8.1 Where the screwshaft diameter as derived by the Finnish-Swedish Ice Class Rules is less than the diameter derived by Pt 5, Ch 6, 3.5 Screwshafts and tube shafts 3.5.1, the latter is to apply.

7.8.2 The diameter, d _s, of the screwshaft determined in accordance with the Finnish-Swedish Ice Class Rules is to extend over a length not less than that to the forward edge of the bearing immediately forward of the propeller or 2,5d _s whichever is the greater.

7.8.3 The shaft may be tapered at the forward end in accordance with Pt 5, Ch 6, 3.5 Screwshafts and tube shafts 3.5.3and Pt 5, Ch 6, 3.5 Screwshafts and tube shafts 3.5.4, except for Ice Class 1AS FS ice strengthening, where these diameters are to be increased by 10 per cent.

7.8.4 For screwshafts in ships intended for the notation Ice Class 1AS FS(+), IAS FS or Ice Class 1A FS, 1A FS(+) or Ice Class 1B FS, 1B FS(+) or Ice Class 1C FS, 1C FS(+) and where the connection between the propeller and the screwshaft is by means of a key, Charpy impact tests are to be made in accordance with the requirements of the Rules for the Manufacture, Testing and Certification of Materials, Ch 5, 3.4 Table 5.3.2 Mechanical properties for acceptance purposes: carbon, carbon-manganese and alloy steel forgings for machinery and shafting.

7.9.1 The diameters of intermediate shafts and thrust shafts in external bearings are to comply with Pt 5, Ch 6, 3.1 Intermediate shafts and Pt 5, Ch 6, 3.4 Thrust shafts respectively, except for Ice Class 1AS FS ice strengthening where these diameters are to be increased by 10 per cent.