KEY POINTS:
When Team New Zealand's new boats NZL84 and NZL92 are powering over the Hauraki Gulf, the syndicate's rig co-ordinator, Martin McElwe has his eyes planted on the 34m-high structure in the middle of the boat.
"We are looking for the stiffness of the mast to support the sail
shapes they want," he says. "With the advent of the bigger tops in the mainsails, the masts have to get stiffer and stiffer."
A foundation member of Southern Spars, McElwee has been involved in every America's Cup since 1992, most recently with Prada in 2002.
He has also worked in round-the-world yacht race teams, on superyachts and maxis.
Over time there have been plenty of developments in Cup masts to keep McElwee on his toes. Most recently there's been the millennium three spreader rig in 2000.
McElwee says a good mast offers stability - "basically so the mainsail and the sails can get the right shape, the mast supports the sails - the sails cannot work efficiently or effectively unless the mast is a stable platform."
During the last Cup, especially during the build-up months, plenty of teams experienced the sickening sound of their mast breaking as they ploughed over waves in the Hauraki Gulf. So far, the only reported mast breaking in Valencia is the German team's this year.
"The change from version four to version five [of the rules] enables us to use materials more robust so there is less chance of failure," McElwee says.
"Generally it is a rigging fitting failure if the masts break because the tubes themselves are quite sound. The minimum weight is quite heavy, you could build a much lighter mast if you wanted to.
"The wind in Valencia is lighter - the few days we didn't sail this year was because the seas were too big, not because it was too windy."
The technology
* 34m, made from carbon fibre. The fibre is laid on a mould and glued with resins. They are cooked in a pressure oven at 135C for up to 10 hours.
* Approximately 4km of cloth, 300mm wide, is built into each mast.
* Built in two sections - each 34m long but half the width. After curing they are then joined together.
* Minimum weight 750kg. There is also a minimum centre of gravity.
* The compression on a rig can reach at least 50 tonnes when the yacht is sailing upwind in a 20-knot breeze - a load equivalent to 33 family-sized cars. The load on the forestay and runners can reach 15 tonnes.
* A mast and rigging cost around $750,000.
* Most of the big teams will build three to six rigs for a campaign, each of which takes about three months to construct.