At the end of 2019, part 7 of ISO 12215 was finalised. Besides the determination of loads, this section also gives calculations for the assessment of Global Loads for multihulls.

The standard provides a simplified method, which is mostly to be used for cruising catamarans. An enhanced method is also provided, which gives a more accurate analysis of results and which is applicable to any structural arrangement.

Overview of Global Loads:

• Quartering sea
• Rig load
• Asymmetric broaching
• Longitudinal broaching / pitchpoling
• Longitudinal force/shock
• Bending on crossbeams of motor multihulls

For typical structural arrangements (multihulls with a significant wet deck), you can use the simplified method. According to the standard, you must check the global structure against the greater of the following two load cases:

• Combination of 100% Quartering sea + 50% Rig load or
• Combination of 50% Quartering sea +100% Rig load

We have developed a structural assessment method by making use of the following software packages:

• Hullscant Software, for the determination of the materials and beam section properties in all kind of materials (including GRP and Carbon).

• Multi frame Software, for the Global Load structural assessment.

FEA beam analysis software has been chosen to keep the calculations within budget. If detailed FAE analysis is required this can be offered as well in cooperation with a partner.

On request, the calculations can be extended with Global mast and rig assessments according to the requirements of ISO/FDIS 12215-10 Rig loads and rig attachment in sailing yachts.

For any questions regarding the ISO 12215-7 calculations, please feel free to contact Wijma Marine Consultants.