In the architectural world, glass structures are becoming more and more important. It is not surprising a similar drive is found in the yacht industry and glass bulwarks, bow sections and even complete glass deckhouses are proposed. The marine industry traditionally just knows glass as plates of fragile material of uncertain origin, necessarily permitted on board to provide view from the control station and daylight to accommodation. Can the yacht industry follow architecture?
Modern glass is a structural material. The mechanical properties as observed in samples of glass of practical size are not far off from those of Aluminium:
Glass is a totally different material than steel or aluminium. Glass is brittle; the load bearing capacity reduces with time; glass is vulnerable to loss of strength after surface damage; breakage is sudden and does not stop, and the variation in load bearing capacity of otherwise identical pieces of glass, even of the same batch, can easily vary by a factor two or more.
This does not mean glass structures cannot be applied safely on board. The traditional maritime design philosophy of ensuring safety by over-design cannot be applied successfully for glass structures. A piece of glass in a structure can fail instantly at any moment in time. The (design) load applied at that moment does not play the main role the maritime industry likes to contribute to it. The design of glass structures is best based on safe performance during the period between the moment of failure and the moment that measures to compensate for the loss of safety can be effectuated. These measures typically are a step-wise approach of clearing the area, preventing further damage or danger and replacement. Each step in this process has its own time scale.
All this cannot be done without deep understanding of the material and the technology of application. The maritime industry is too small and too fragmented to develop such by itself. Knowledge about load bearing capacity can be obtained from architecture and the building industry. Knowledge about the loads that can be expected to act on a floating structure in a sea environment is well available in the maritime industry itself.
When glass panels make 90 percent of the outside area of deckhouse walls it makes no sense to treat them as appliances to close an opening. The glazing system has become a key element in the structural design and therefore should move from a statutory aspect to become part of classification.