Orientation of the fibres
The accuracy and orientation of the fibres laid down will also govern the performance of the laminate and in pure compression terms you will get a fall in performance if the fibre is even slightly off axis. However a percentage of off axis fibre will always be required to stabilise shape and allow for torsional loads. We commissioned independent research and testing in early 2002 to analyse laminate structures. They confirmed that when carbon fibre is working within a laminate structure, to achieve optimum performance in both longitudinal and torsional stiffness fibres could be laid down at between 8° to 21° degrees depending on the degree of torsional stiffness required while still exceeding strength requirements. Using this information we have optimised our winding process to ensure greater accuracy of angle as well as perfecting techniques to wind different angles through the length of the spar to maximise stiffness and bend in each panel. This process combined with local hoop and patch reinforcements provides really light, stiff and robust carbon spar sections. Conclusions
It is not important whether the laminate is constructed with 0° and +/-45° fibres or with “off” axis fibres - the required weight, strength and stiffness for a performance spar can be achieved either way.What is critical is that: The orientation of the fibres is • accurately controlled - it should not be done by hand. That the resin content is accurately • controlled and is as low as possible. That the laminate is well consolidated • with close to zero void content (cured in an autoclave). Southerly 46 powered by Seldén carbon mast. Photo courtesy of © Northshore Yachts 7