ISO 12215-7:2020

Overview

ISO 12215-7:2020 - "Small craft - Hull construction and scantlings - Part 7" defines how to determine local design pressures and global loads for multihull small craft (catamarans, trimarans) with a hull or load line length up to 24 m. It sets out the dimensional data, load cases and assessment scope used to calculate panel and stiffener scantlings by reference to ISO 12215-5 and to assess stability/buoyancy in conjunction with ISO 12217. The standard applies to recreational and commercial multihulls built from the materials covered in ISO 12215-5, and to structural elements supporting windows, hatches, doors and similar openings.

Key topics and technical requirements

• Scope and limits: Multihulls ≤ 24 m (hull or IMO load line length); excludes professional racing craft.
• Load definitions: Local design pressures for panels and stiffeners, and a set of global load cases (GLC1–GLC6) including diagonal quartering seas, rig loads, asymmetric broaching, longitudinal pitchpoling and crossbeam bending.
• Dimensional data: Main dimensions, areas, bottom deadrise, wet-deck geometry and crossbeam geometry required for load assessment.
• Panel and stiffener assessment: Methods for local pressure application - constant averaged pressure, alternative assessment techniques and “natural” stiffener behaviour.
• Adjustment factors: Local pressure-adjusting factors and limits of loaded areas to refine design pressures.
• Global loads & structural arrangements: Simplified and enhanced methods for global load analysis, design stress treatment, and arrangements for supporting loads (including crossbeams and hull attachments).
• Documentation & guidance: Required owner’s manual information, details for commercial/workboat use, and informative annexes (FEM practice, torsional analysis examples).

Applications and who uses it

ISO 12215-7:2020 is used by:

• Naval architects and multihull designers for determining scantlings and structural layout
• Structural engineers performing load and FEM analyses for catamarans and trimarans
• Boatbuilders and shipyards for construction specifications and compliance checks
• Surveyors, class societies and regulatory bodies assessing structural adequacy
• Owners/operators and fleet managers (guidance provided in owner’s manuals)

Practical uses include designing crossbeams, sizing hull panels and stiffeners, evaluating rig attachments for sailing multihulls, and preparing compliance documentation for recreational and commercial craft up to 24 m.

Related standards

• ISO 12215-5 - Assessment of scantlings from local design pressures (required referenced method)
• ISO 12217 - Stability, freeboard and buoyancy assessments
• ISO 12215-6, -8, -9, -10 - Additional details for materials, rudders, appendages and rig loads

Keywords: ISO 12215-7:2020, multihull loads, small craft scantlings, local design pressures, global load cases, ISO 12215-5, catamaran design, trimaran structure, crossbeam bending, FEM guidance.