Section 1 Rule application
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Special Service Craft, July 2022 - Part 5 Design and Load Criteria - Chapter 1 General - Section 1 Rule application

Section 1 Rule application

Parent topic: Chapter 1 General

1.1 General

1.1.1 The global and local load and design criteria detailed in this Part are to be used in conjunction with the formulae given in Pt 6 Hull Construction in Steel, Pt 7 Hull Construction in Aluminium and Pt 8 Hull Construction in Composite to determine the scantlings of steel, aluminium alloy and composite craft respectively as defined in Pt 1 Regulations.

1.1.2 The global load and design criteria given in this Part are provided to enable the designer/Builder to check global hull strength against ductile failure modes involving gross deformation. The strength calculations are, in general, to be conducted using finite element analysis techniques with a three dimensional model.

1.1.3 Load and design criteria detailed in this Part are to be supplemented by direct calculation methods incorporating model test results and numerical analysis for novel designs. Full scale measurements may be required where considered necessary by Lloyds Register (hereinafter referred to as LR).

1.1.4 Where an operational envelope is assigned it will be based on the allowable speeds, significant wave heights and corresponding displacements. Installation of an accelerometer at the LCG with a visual display in the wheelhouse may be required.

1.1.5 The operational envelope assigned is based on the assumption that the wave height can be visually observed. Where this is not the case, the speed of the craft is to be suitably reduced.

1.1.6 The design assessment is to include a range of speeds covering all modes of operation for which the craft is designed, i.e. speeds corresponding to displacement, semi planing and fully planing. A craft which is designed to operate in the planing mode will need to be assessed using the requirements of Pt 5, Ch 3 Local Design Criteria for Craft Operating in Non-Displacement Mode at its design speed and required significant wave height, as well as the requirements of Pt 5, Ch 4 Local Design Criteria for Craft Operating in Displacement Mode when operating at reduced speed and a more severe wave height.

1.1.7 The load design criteria given in this Part are dependent on the operating mode of the craft as follows:
  • Craft operating in the non-displacement mode:
    • Applies to craft operating in full planing or semi planing modes.
    • Applies to craft in foil borne mode.
    • Applies to craft where other lifting devices are actively supporting some or all of the craft’s weight.
    • Typically this applies to craft with a Taylor Quotient, Γ , greater than 3. Γ is defined in Pt 5, Ch 2, 2.1 Parameters to be used for the determination of load and design criteria 2.1.17. However, the following is to be noted:
      • Some craft are not designed to plane, but have Γ greater than 3, e.g. SWATHs, fast displacement yachts, wave piercing and low wash catamarans. These craft are to be considered as only operating in the displacement mode.
      • Some craft are designed to plane with Γ less than 3 and these should be considered as operating in the non-displacement mode.
  • Craft operating in the displacement mode:
    • Applies to craft designed to operate in the displacement mode.
    • Applies to all other craft where they are not operating in the non-displacement mode, e.g. at lower speed in severe weather.
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