ISO 12215 is the series of standards setting hull construction and scantlings for recreational craft up to 24 metres. On the structural side, it is the main reference when showing conformity with the EU Recreational Craft Directive.
Parts of the series
- Parts 1-3
- Materials: thermosetting resin and glass-fibre laminates, sandwich core materials; steel, aluminium, wood and others.
- Part 4
- Workshop and manufacturing.
- Part 5
- Design pressures, allowable stresses and determination of scantlings.
- Part 6
- Structural arrangements and details.
- Part 7
- Multihulls.
- Parts 8-10
- Rudders, keels and appendages on sailing craft, rig loads and rig attachment.
What it means in practice
- The designer calculates skin thicknesses and stiffening to this standard, for the boat's design category and speed.
- The yard builds to the calculated laminate schedule and details.
- Supervision compares the structure built with the structure calculated: ply count, thickness, stiffener spacing.
In refit and modification
For structural changes such as keel, rudder, engine beds or deck openings, calculating the new detail to the same standard keeps the boat's conformity intact.
Continue with this topic
- Calculation approval: Structure, stability and weight.
Parts of the standard
ISO 12215 covers small-craft structure in several parts. The first parts deal with materials: resins and glass reinforcement, core materials, steel, aluminium and wood. Part 4 sets workshop and manufacturing conditions. Part 5 covers design pressures and scantlings for monohulls, Part 6 structural arrangements and details, Part 7 multihulls. Later parts cover rudders, appendages such as keels on sailing craft, and rig loads. The standard applies to recreational craft within a defined length range.
Why it matters to the owner
The standard shows by calculation whether the structure is adequate for the loads the boat will meet. Read with the design category, it is the structural basis for the sea conditions in which the boat can be used safely. For the owner, it replaces a phrase like "strong hull" with a measurable yardstick.
Where calculation meets production
A calculation can be right on paper; what matters is that production follows it. Laminate thickness, ply schedule, fibre content and the position of structural members are checked during the build. If the fibre content in the calculation is not reached, the laminate can be heavier and weaker; so production records also prove the calculation.
Whose job is it?
The designer does the calculation; in the CE route a notified body assesses it. The inspector's job is to see and record at check points that production follows it. On boats built to class, class rules may apply instead of, or alongside, this standard.
How it goes in the specification
The specification states which standard the structural calculation follows, that the calculation and laminate schedule are annexes to the quote, and which measurements will verify them during the build.
For used boats
On a used boat, the original scantlings are rarely available, but the design category and builder's documents show what the structure was designed for; the survey reads the boat's condition against that.
Where the original calculation is missing, the builder can sometimes supply the laminate schedule on request.
That information makes it easier to follow the original ply schedule when a repair is planned, and so has a direct effect on the quality and value of the repair.
The repair record joins the boat's papers and is asked for at sale.
A documented repair builds trust.