Most boats are built for speed and stability, but Plastiki, like its namesake the Kon Tiki, was a concept vessel designed to grab headlines while testing various PET-based materials and alternative energy concepts.
With the journey completed and the boat safely moored, eco-adventurer David de Rothschild and his company Adventure Ecology can review the success of the materials and designs trialled on the boat de Rothschild called “a symbol of solutions”.
The striking 12 500 bottle-strong design honed by Australian naval architect Andy Dovell (award-winning designer of the H2 surfboard fin) is likened by de Rothschild to a pomegranate, the dry ice-filled bottle ‘seeds’ providing sixty-two per cent of the ballast grouped together to form the hulls, but also separate enough that one or two failures would not mean dis-integration.
For publicity purposes the bottles were left revealed and the resultant drag meant that Plastiki sailed equal parts sideways and forward with direction limited to downwind and broad reach only.
Although hydro-dynamically inefficient, the unskinned bottles visually conveyed the PET-content of the vessel to audiences around the world. Less visually captivating but far more transformational is the material invented in Europe and trialled on the Plastiki voyage, a PET-based material named srPET.
Self-reinforcing plastics gain advanced strength and stiffness from their highly oriented polymer fibres with typically five times the stiffness and strength values of unreinforced plastic. srPET is used as a structural skin on all the non-bottle surfaces of the boat including the Buckminster Fuller-inspired geodesic cabin.
srPET is expected to compare in strength and usefulness to fibreglass, but with none of the health issues associated with glass fibres, and all the recycling benefits of being a homogenous plastic material.
This thin skin of srPET along with the srPET board material used in the hull structure currently require virgin polyethylene terephthalate, but the srPET textile used for the sail utilises recycled PET and is bonded with a specially developed organic glue made from sugarcane and cashew nuts and is currently being commercialised by Adventure Ecology.
A postmortem on the voyage of the Plastiki revealed a crew reluctant to set sail on a bottle raft again any time soon, but enthusiastic at the success of the srPET iterations trialled over the months at sea.
Composites Evolution, the UK company behind the Aptiform PET-based products including srPET and the more commonly known srPP, suggest that the light weight, low cost and recyclability of srPET is particularly applicable to large, low-volume parts, making it an ideal material for sustainable transportation applications, including sea-going vessels.
The beauty of Plastiki was in the details – all the parts of the boat were not made of PET bottles on this voyage, but probably will be on the next.