with the datums. There are jig sets for all of the fittings, spreader roots, rigging attachment points and everything else, so that they come out of the shop millimetre perfect. ‘We go to great lengths to make
sure these rigs really are all the same,’ says Lance. ‘Everything about them as they go through manufacture is weighed and checked and recorded in their own file, known as a Blue Book. It’s extremely important that we get the one-design aspect of the masts correct. ‘All of the sailors want to know
they have got a mast that is just as good as the rest of the fleet, so we put a massive emphasis on it because we want to be sure that it is a fair race. It’s the same as it is with the hulls and the sails. Sure, the sailors need an even platform… but they also need to believe that they have that even platform.’ The average weight of the 11 complete masts delivered for the 2014-15 race was 415.2kg. The difference in weight between the lightest and heaviest just 1.35kg, or 0.32 per cent. The tube length of those masts is 28.4m, however the range in the balance point, or centre of gravity among the masts is only 30mm, which makes them identical to 0.12 per cent. In terms of bend profile, before
course the geometry, the length of the tube and the location of the fittings. However, other factors like weight, centre of gravity and bend profile, all critical to performance, are much harder to control. ‘For everything that we manufacture we apply a stringent array of checks – these start with ensuring that the physical material we put into a spar is up to standard and is going to behave the way that we expect,’ says Dr Chris Hickey, Southern Spars’ head of Materials and Process Engineering. ‘For every batch of raw pre-preg
carbon fibre we test the weight, resin content, tack, bleed, glass transition temperature, interlaminar shear strength and cured ply thickness, before it is released for production. Then, for each mast we manufacture, a witness panel manufactured in parallel with the mast is tested again for glass transition temperature, interlaminar shear strength and cured ply thickness. This guarantees the as-built mast meets our precise specifications.’ Ensuring that the material that goes into each mast is the same is
Above:
having used their spar making skills to deliver a complete America’s Cup-winning catamaran (their first
boat) it’s back to business as usual at Southern Spars. As the laminate layers get thinner and thinner with the use of Thin Ply
Technology (TPT) it’s more essential than ever to automate
production to ease issues of accuracy and also the physical handling of such fine
materials. But there’s plenty of scope still (top) for
human input
the first step in making sure the final products will be within the one per cent accuracy window set down by Volvo Ocean Race management. As the raw material is laid into
the mast moulds, every individual layer is then checked and signed off, making sure that it is in the right place with the right orientation (within the moulds themselves there are also a series of datum marks used later as reference points for the accurate placement of fittings). Once cooked, each tube is NDT
tested with ultrasound to check that the finished laminate meets expectations throughout. The weight of the mast shells and every component that goes onto them is also weighed at every stage and tracked to ensure each spar remains within that magic one per cent. ‘Once the masts are into the
fit-out stage we slot them into a set of cradles that are bolted to the floor, and then line up all of our jigs,’ says Lance Manson, Southern Spars’ project manager for the Volvo masts. ‘The jigs make up a series of guides for cutting and drilling holes and they get aligned
leaving the factory the rigs are supported at either end and a 400kg weight is suspended from the middle and bend response carefully mapped. The range of bending deflections across the 11 spars was recorded at just 1.4mm. On a spar nearly 30m in length… The proven repeatability of the Southern Spars process was a key to winning the contract to build a new round of masts for the 2017-18 race. Teams were given an option of using the existing mast in their allocated boat or buying a new one, which all but two teams chose to do. However, one-design is not the
only thing on Southern Spars’ mind. ‘Safety is of the utmost importance for us too,’ says Lance. ‘Not just on these masts, but in all of the masts we make. ‘In the conditions these guys are
going into there aren’t any second chances; we have to make sure the masts and the rigging are safe. The rigs get pushed hard, harder now because of the one-design nature of the current race – whoever can push the hardest for the longest is going to win. As long, of course, as they are pushing in the right direction. So, simple really!
www.southernspars.com
q SEAHORSE 57
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