Carbon fibre masts

Southern Spars' David Barnaby looks at the new rigs on Volvo Ocean 60s

Carbon fibre comes in in various forms. For the production of V.O.60 masts the carbonis used in a prepreg form, with the epoxy resin incorporated in the fibres by the manufacturer. Epoxy is a thermosetting resin, which means that it cures and sets with heat.
The carbon/epoxy material is laid up in a mould, layer by layer, and cooked in an oven to a maximum temperature of 125°C to effect a cure. This results in an extremely light and stiff product. Wall thicknesses vary from 5-15mm which equates to anything between 15 and 45 layers of cloth.

Sensibly, the Volvo Ocean race Rules Committee have put a limit on the stiffness of the carbon used and on the maximum curing temperature for the resin. This ensures all masts are similar and that no team gains an unfair advantage.

The V.O.60 Rule is intended to promote boats that are fast, seaworthy and strong in order to withstand the rigours of a hard driving crew. In previous races we have seen aluminium masts fall over the side due to both crew error and rigging attachment failure.

Being both stronger and stiffer carbon rigs are less likely to suffer the same fragile catastrophic failure and are therefore undoubtedly safer. Bear in mind that if a boat loses its mast on either of the Southern Ocean legs, they will be far from land and help, a situation which befell both Silk Cut and EF Education in the last race.

The performance of the boats has increased due to less weight aloft. The all up minimum rig weight for a V.O.60 is now 565kg whereas in the last race it was unlimited, with the masts ending up around 620kg. With each team gunning for victory no one will be wanting to leave the dock with a rig that is overweight.

With a minimum all up weight for each boat the only way to get things under control if the various components are heavy is to shave weight off the bulb. This begins an ugly spiral of lower stability affecting overall performance.

The V.O.60 Rules Committee have done a good job at keeping the rig weights conservative for such a tough race. It would be possible to use the same materials and build a rig significantly lighter with a lower centre of gravity. With no minimum weight in the previous race, the aluminium rigs ended up being fragile and could not stand the loads that are being exerted now with the development of the large Code O free flying headsails.