KEY POINTS:
Some of the developments we can expect to see at Valencia next year:
SQUARE TOP MAINSAIL
Devised by Alinghi in the last Cup, the square top mainsail aims to make better use of the wind at the top of the mast which is usually stronger than at the bottom.
Squaring the mainsail off at the top effectively creates more sail area than a traditional triangle-shaped sail.
With the square top, the diagonal top batten supports the leech (the trailing area of the sail), which means the leech can be much flatter and create less drag.
The square top is also much easier to control the twist with. Having a mainsail that twists easily and is able to flatten out easily makes the gear changes almost automatic when a puff hits.
Alinghi are testing a black mainsail which is constructed differently.
Fallow: "We understand what it is, we know where the potential gains are. When we last saw it, it needed work, it wasn't a raceable product as we saw it. It is closer to building a boat than a sail the way they have built it."
DOWNWIND SAILS
In an effort to turbocharge the yachts, bigger downwind sails have been introduced.
They are now in excess of 500sq m and have to be constructed from nylon or polyester and cannot include cuben fibre - an expensive and explosive fibre used last time.
Team New Zealand build their spinnakers in-house using North Sails' design software.
Fallow: "We can build a spinnaker in a day and a half if we have to. That is why we chose to do it ourselves this time. If we see something or come up with an idea, we can respond quickly."
The difference between a good downwind sail and a bad one can be measured in terms of several per cent of driving force difference, he says.
"That is something a keel or rudder designer would die for, it would be big news if they came up with a bulb which was 3 per cent less drag on the whole boat. All of the top teams are spending a lot more resources on sails."
HEADSAILS
The advances include inflatable battens and increasing roach (curve). More roach in the headsail helps to capture the breeze better, which produces more speed.
While the mainsail has carbon-fibre battens to maintain shape, the headsails can now be fitted with inflatable battens which don't break when flicked across the mast when the boat tacks. The battens help to keep the sail taut when sailing in a straight line.
They were a challenge to begin with.
Fallow: "Less than two years ago we were sitting here saying, 'We are going sailing in six weeks, what are we going to do?'
"We had a bit of firehose and were trying to pump something up. Six weeks later we came up with a solution and we have developed a lot since then. We are pretty happy where we have ended up in terms of weight, tackability, etc.
"It is certainly one of our secrets we have wanted to guard because it took a lot of good thinking to get it to work."
TWISTING RIGS
Another Alinghi innovation in the last Cup, the twisting rig is a concept designed to help to reduce the wind resistance of the mast. The idea behind it is to line the mast up to the apparent wind to reduce the drag.
Devices cannot be used to twist the mast, the forces of the sails do it.
Since the last Cup, the rules have been relaxed.
McElwee: "There is a limit that the mast is allowed to twist two degrees at the deck. Last time the mast was allowed to twist two degrees at the deck but only half a degree at the base. This time they took the base restriction away. A lot of teams try and twist the mast for better aerodynamics, really.
"In the scheme of things it is not huge, a multihull might twist the mast 30 or 60 degrees - where we are only talking about a couple of degrees."
Most of the teams are experimenting with the concept.
JUMPERLESS RIG
Positioned on the mast, jumper struts and stays support the top of the mast. The benefit of no struts is less windage but the challenge is to ensure the mast section is strong enough to handle the loads without the normal level of support that jumpers and stays provide.
McElwee: "The weight lost in the jumper struts will go back into the mast tube itself and generally the mast is a bigger size to help support it."
This is the first Cup where the concept has been seen with both Alinghi and Oracle sporting jumperless rigs.
SPREADERS
Team New Zealand pioneered the three-spreader "millennium rig" for the 2000 Cup defence.
They went back to a four-spreader rig in 2003 and have stuck with the concept for Valencia.
They are the only team sporting a four-spreader rig.
The tradeoff is between stability, support and windage.
McElwee: "The masts weigh the same at the end of the day. You have this weight to spend - you can spend it on the tube or the rigging or a combination. You could put really heavy rigging on and less carbon in the mast tube or light rigging and more carbon in the tube. It's a tradeoff between what you want really."
