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from bits to nuts and bolts
building techniques
some basic considerations on appropriate building techniques for large double-curved surfaces. after the competition a lot of speculations arose concerning the mysterious material of the blue bubble. the winners had made a proposal that pointed towards a technique known from sailmaking - 3dl. although this was not feasible in tems of a 1:1 adaptation for an architectural project it turned out that something quite related to 3dl had been done before. the structural engineers for our project, bollinger + grohmann, had developed a small pavillion for bmw in 1999 (together with architect bernhard franken) which resembled the shape of a waterdrop and was made out of several hundred double-curved (means that both x- and y-axis of a surface are not straight) and individually formed acrylic sheets mounted on an aluminum frame structure. this was a technical inspiration for us and it proved that we could try something similar for the kunsthaus project. (and i think that b + g were very keen to use their knowledge again - but in a different context.) so we were a bit biased about the choice for the material at a very early stage. to explain the reasons for this i will go back to the alternatives we had: shipbuilding: double-curved hulls have been commonplace in shipbuilding for a long time and many different techniques have been tried out in wood, steel, concrete and plastics. larger ships are one-off pieces and follow a construction process that is similar to the one used in the building industry. a recent example of a building that adapts techniques from shipbuilding is the press stand for a cricket stadium designed by the architects future systems (see their fantastic book) actually the building was prefabricated in a wharf (a procedure which the client would not easily accept) and done in aluminum sheet metal that had been bent to a double-curved shape. it is a very labor-intensive process and can only be done by very specialized companies. but the main disadvantage is that there is no way to make it transparent and double curved. casting: in industrial applications some materials can be cast into any shape you like but usually the cost of the tooling is the most influential constraint. this applies to concrete shuttering and even more to the glass or plastics industry and is the reason why so many plastic materials (like concrete) usually appear in very straight shapes. in general it is not useful to do a one-off piece from an expensive mould - so what is really the task is to find a mould that is cheap to manufacture or one that can change its shape. in the sailmaking industry the 3dl system uses a mould that is flexible to a certain degree but can not precisely follow an arbitrary curvature.