AC mains

Images of the flat-topped mainsails and sail technology being used in the America's Cup

One area of technology that America's Cup teams have been developing in recent months is square topped mainsails. The theory goes that wind strength is greater 100ft up than there is at deck level and therefore the more sail area you have higher up by increasing the roach, the more efficent use you are making of your sail area. This technology has slipped into America's Cup Class boats from the French multihull circuit where mainsails of this type have been used for some time. While multihulls are inherently stable due to their multi-hull configuration, America's Cup boats are also extremely stable thanks to their 20 tonne keel and thus they are able to hold this powered up sail area.

Of course 100 years ago sailing ships used to have mainsails of this shape, but they had a gaff to support the leach. Without a gaff, AC sailmakers have to use a variety of different batten architecture in the heads of their mainsails. The most extreme flat-topped mainsail is to be seen on Emirates Team New Zealand's NZL 82.

More photos on the following pages...