In order to fight the economic crisis and to sustain the contest with competitors super yacht field is even more driven by new aesthetic criteria and interior philosophies proposed by trendy designers. Often some of these new aspects involve binding complications to stability and structural strength, like in the case of large openings and docks to recover tenders. Another tendency recently introduced by designers is to enlarge windows to allow a more efficient lighting of internal living spaces. So large windows have replaced small porthole in the hull, with easily imaginable implications on the hull strength. The same philosophy has been applied to superstructures where usual windows leave room to large glass doors extended from deck to deck to allow light to come in and the passenger to have a wide view of external landscape. Very nice innovation but big troubles bearer. In fact in areas where this doors are fitted the structure is reduced to the minimum: very slender vertical stiffeners represent the only structural components. In this case the resistance to compression load should be carefully evaluated in order to avoid buckling phenomena. The problem is further complicated by the fact that superstructures are usually made by aluminum light alloy the resistance of which to compressive loads is reduced by the low elastic modulus. This implies several problems, all related to superstructure structural behavior and to their level of cooperation with hull structures.

In this paper the contribution to hull strength offered by light alloy superstructures of large motor yachts and some buckling phenomena occurred in large opening areas is investigated by finite element approach. The analysis of in force rules for superyacht superstructure scantling is assessed as well in order to verify by direct calculation their confidence level.