Master thesis : A consideration of the ISO12215 Structural Rules and the Classification Rules for a Vessel Close to 24m in Waterline length

Abstract

Yachts and other recreational crafts are a growing market. Depending on the length, these vessels are subject to different rules and regulations. For scantling of boats with a length smaller than 24 m, ISO 12215 Structural Rules are applied. Above this length, yachts are designed following Classification society rules. Scantling by structural regulations, stipulated by both ISO and Classification societies, has a common pathway.

A high-speed motorboat was selected to assess the for impact of slamming load and acceleration of gravity on the design. The assessment of minimum design loads, computed by ISO and Classification societies’ rules, is done by comparing the definition of design pressure, its longitudinal distribution, effect of gravity acceleration and effect of deadrise angle.

Afterwards, the scantling of a bottom plate is done by using the ISO and Classification societies’ rules. The material of the motorboat is composite, with a sandwich structure. Minimum requirements demanded by the rules are assessed. Limitation criteria stemming from breaking strain or ultimate stress are evaluated parallelly with core check for shear.

Finally, the results are compared, with the purpose of verifying if there is a natural structural continuity between a 24m yacht designed with ISO and with another designed with Classification society; plating should be similar and there should not be and big jump in laminate thickness and strength requirements, which was not the case. The inconsistencies between the results were analysed.