The journal

Engineering the impossible 1/02
Francesco Fiorentino

A famous phrase of Albert Einstein says: “Everyone knew it was impossible, until a fool who didn't know came along and did it”. This phrase perfectly fits what happened right before my eyes with the big difference that the persons who managed to make something that up to then seemed impossible knew exactly what to do! That’s what happened one day about two years ago when in MICAD we started a challenge with Moi Composites in an ambitious project called Mambo.

If a few months ago someone told me it was possible to produce a product in composites using additive manufacturing I would certainly have thought it was a joke, let alone printing an entire boat, and one that sailed to boot! In this short article I will recount for you a part of this adventure which is still unfolding. Representing an absolute and undisputed first in Italian boatbuilding and brilliance! It was Mambo, the first boat in composites in the world to have been built entirely without using moulds and models but completely in additive manufacturing.

What’s more, it can also sail. A new technology, a breakthrough idea and lots of creativity: these are the key points of a new conception of composite construction that could revolutionise yachting in the next few years. Just think that only 70 years ago aeroplanes, cars and trains were mainly built in sheet metal with, in some cases, wood, while today these materials have been almost completely replaced by more or less advanced composites. This rapid spread was a result of the ease of production, the ease of finding materials and the high repeatability of products. Yachting, unlike other sectors of the transport industry, was initially very suspicious of this change. It would seem, then, that composites are the ideal solution for any kind of construction and can be used to create any kind of product of whatever shape; in fact this is partly true as shown by the increasingly extreme and organic lines that yacht designers propose for hull geometries, decks and superstructures, but it is not always the case that everything that appears simple actually is. Resin impregnated fibres cannot be freely modelled by hand or with special tools as happens with sheet metal or wood. Products in composites are obtained using moulds so that the fibres, suitably shaped and laid down, take on the shape desired. In addition the moulds must necessarily be open and/or openable to allow operators to position at least the fibres (the resin can also be introduced by vacuum infusion). This is a first (and often major) limit to construction in composites. The need to have a mould that acts as a “container” that holds fibres and resin until they are catalysed means that the product, after moulding, must also be extracted from the mould. If the geometries allow this (so do not have elements and/or shapes that impede extraction) this is not a problem, but if a component needs to be made with a geometry that prevents its extraction this complicates matters. In this case there is the need to produce moulds that can be broken down in several parts and held together by flange is bolted together or to insert inside the moulds so-called inserts (or plugs). The need to extract the component from the moulds demands in-depth study of the final shapes and any dismantling of the mould to avoid the component being trapped inside it with very negative consequences for costs and production. If we had to respect these two rules by the letter we would probably only see on the water boats looking more or less like boxes, but fortunately this is not the case.

Every element made in composites needs a mould which in turn is produced by a model which after use must first be stored for a (hopefully) short period of time and then disposed of. The same is true for the moulds and these often cost a lot to dispose of, so manufacturers prefer to store the moulds in sheds or often in the open. All this requires a lot of economic resources and a waste of material but above all a major environmental problem because until a few years ago producers and designers of composites never took into consideration a life cycle assessment. ( be continued)

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