Auckland's higher winds and generally smoother seas have seen a significant shift in sail shapes and rig configurations compared with the 1995 San Diego generation. Sails are cut much flatter and sheeted much harder on rigs that are much stiffer than before -- all of which makes for an unforgiving cocktail of forces that sends the loads rocketing to numbers never seen before on International America's Cup Class yachts.

Steve Wilson of Southern Spars, which built Team New Zealand's masts in 1995 and again for this regatta (along with Prada and Abracadabra), said their rigs are even stiffer this time round and are having to cope with compression loads over 100,000 pounds with forestay loads up to 30,000 pounds. "It's exciting and frightening at the same time," said Omohundro's Terry Kohler of the technological advances and challenges these loads represent. Omohundro has made masts for Team Dennis Conner, AmericaOne and America True, among others. "Our masts are literally 50 percent stiffer than they were in 1995."

The demand on the masts has increased also because the Auckland generation of yachts has narrower shroud bases and because sheeting the sails harder means the spreaders have to be shorter. "Everything is getting closer to the centreline," said Tom Whidden, CEO of the North Marine Group and a long-time Conner sidekick.

"The actual sheeting angles at the deck are not much different from San Diego, generally between seven and nine degrees, sometimes as close as 6.5 degrees. But, because the headsails are flatter and sheeted more tightly, the middle of the sail is drawn in much closer to the rig, requiring the narrower spreaders. "All this means the tacking angles can be much narrower. On many days, we are tacking through 60 degrees, whereas it would have been about 70 degrees in San Diego," Whidden said.

With most teams opting for a very high carbon content in their sails, there is also much less stretch than before. In the 1995 sails, there would have been about 10 units of stretch for every 100 units of load. "Now we are down to about two units of stretch for the same load," says Whidden. "It is so small, it virtually cannot be measured."

Carbon-fibre hulls, with heavy keel bulbs provide very stable platforms, too. Combine that with stiffer masts, halyard locks and aramid running backstays, and it all adds up to a system with virtually no give in it anywhere. It is all strung tight as a harp, with all the elements working much closer to their maximum loads.

This, in turn, has meant going up in rigging sizes, shackle sizes, traveller systems -- everything that carries load is carrying more load this time and has to be built correspondingly stronger. Underestimating that reality has seen two boats suffer rear bulkheads ripping out under fairly benign conditions -- which doubtless sent all the other syndicates scurrying to rerun their numbers and possibly reinforcing their structures.