Section 6 Strengthening requirements for navigation in ice conditions

6.1.1 Where an ice class notation is to be included in the class of a craft, the scantlings will require special consideration, see Pt 3, Ch 2, 9 Navigation in ice.

6.2.1 It is assumed that single skin laminate construction incorporating longitudinal or transverse stiffening will be adopted. Where it is proposed to use sandwich skin construction, particular care is to be given to the selection of the core material; such proposals will require to be specially considered, and testing may be required to demonstrate the suitability of the panels.

6.2.2 In way of the main ice belt zone, the thickness of the shell laminate is to be determined by direct calculation. A copy of these calculations is to be submitted for consideration.

6.2.3 Changes in laminate thicknesses are to take place gradually, and in no case is the length of taper to be less than 20 times the difference in thickness. Additionally individual plies of the laminate are to be arranged such that any delamination will be directed to the outer surface of the laminate.

6.3.1 The web thickness for ice framing members of top-hat or plate section is to be determined by direct calculation. A copy of these calculations is to be submitted for consideration.

6.3.2 Ice frames are to be attached to the shell plating by double primary bonding angles in accordance with Pt 8, Ch 3, 1.19 Boundary bonding. The web area of ice frames is to be maintained; air and drain holes are to be kept to a minimum.

6.3.3 The bending moment assumed to be carried by the ice framing stiffening member is not to be taken as less than 50 per cent greater than that required by the appropriate Section of the Rules for the stiffening member subjected to hydrostatic or pitching pressure whichever is the greater.

6.4.1 The stem is to be additionally protected/reinforced by a metallic shoe or other equivalent arrangement. The shoe/reinforcement is to extend from the keel plate to 750 mm above the ice load waterline and is to be internally strengthened by closely spaced floors, brackets or webs. Details of such protection and the method of attachment are to be submitted for consideration.

6.4.2 Attachment by mechanical means such as bolting or other methods is not to impair the watertight integrity of the craft. Through bolting of the hull is to be kept to a minimum and avoided where practicable.