ISO 12215-5:2019

Overview

ISO 12215-5:2019 (Corrected 2023-11) - "Small craft - Hull construction and scantlings - Part 5" defines design pressures, design stresses and scantlings determination for monohull small craft. It applies to recreational craft, recreational charter vessels, small commercial craft and workboats up to 24 m hull length (LH) or load line length. The standard covers watertight/weathertight structural parts used when assessing stability, freeboard and buoyancy (see ISO 12217) and complements other parts of the ISO 12215 series.

Key topics and technical requirements

• Design pressures and local loads for monohulls (motor and sailing craft), including bulkheads, windows, hatches, doors and outboard engine loads (informative Annex K).
• Design stresses and mechanical properties for common construction materials: fibre‑reinforced plastics (single skin or sandwich), aluminium and steel alloys, glued wood/plywood (excluding traditional wood), and non‑reinforced plastics for craft <6 m.
• Scantlings determination methods - six accepted methods: Simplified, Enhanced (ply‑by‑ply), Developed, Direct test, FEM (Finite Element Method) and Alternative drop test. Annexes provide detailed calculation procedures (FRP, sandwich, wood laminates, stiffeners, laminate stacks).
• Panel/stiffener geometry, pressure adjustment factors and area reduction factors, and specific requirements for watertight bulkheads, integral tanks and keel-related reinforcements.
• Units and conventions: SI units (m, m2, kg, N, kPa, N/mm2), and notation conventions (Max(a;b;c), min(d;e;f)).

Applications and who uses it

ISO 12215-5 is used by:

• Naval architects and marine engineers for hull structural design and scantlings calculations.
• Boatbuilders and manufacturers to size plating, stiffeners and sandwich cores, and to select materials and ply schedules.
• Classification societies, surveyors and regulatory bodies for conformity assessment of small craft.
• Design offices using numerical analysis, since the standard explicitly allows FEM and other advanced methods for load/stress assessment. Practical uses include verifying hull plating thickness, stiffener spacing, window/hatch support structures, bulkhead design, and documenting structural safety for owner manuals and certification.

Related standards

• ISO 12215 series: Part 7 (multihulls - local pressures), Part 8 (rudders), Part 9 (appendages), Part 10 (rig loads and attachments).
• ISO 12217 (stability, freeboard and buoyancy) and references to the IMO International Load Lines Convention for load line definitions.

Keywords: ISO 12215-5, small craft scantlings, monohull design pressures, hull construction, design stresses, FEM boat design, FRP laminate calculations, aluminium boat scantlings.