Zana explained

Designer Brett Bakewell-White on the nuts and bolts of his latest maxi

The Cruising Yacht Club of Australia, organisers of the Rolex Sydney-Hobart, have come in for criticism from the owners of boats like Mari Cha, Bols and particularly Alfa Romeo's Neville Crichton for placing a size limit on their race fleet of 100ft and 1.61 under IRC. While there is a strong argument that the rating limit is too low and doesn't reflect the type of high performance maxis that are capable of being built (and that most owners want to build) today, there is no denying that without this limit there would not have been the cut throat battle between Grant Wharington's Skandia and Stewart Thwaites' Zana in this last Rolex Sydney-Hobart.

Both these maxis are bang on the maximum rating and length limits, but otherwise they could not be more different: While Skandia has a canting keel (albeit only swinging by 12degrees) and an adventurous beefcake of a rig with two giant spreaders, Zana has a fixed keel with a trim tab and a five spreader rig.

Prior to the start of the Hobart race it seemed probable that Zana would be the better on or off the breeze, while the canting keel Skandia would prefer reaching. Post race none of the crew we spoke to on either boat revealed there being much to choose between the two boats on any point of sail, perhaps indicating what an effective leveller of the playing field the IRC rule is.



Designer Brett Bakewell-White and Zana

Last week we spoke to Don Jones about the radical Skandia , today we look at the more conventional Zana, a design by Auckland-based architect Brett Bakewell-White (to read more about the background to the Bakewell-White design team - click here).

Bakewell-White explains the rationale behind the design of Zana: "Stewart [Thwaites] came to us and said that he firstly wanted a boat that was going to get to Hobart. From the engineering brief, the structural side was very important to him and he had to know that if they needed to they could drive the boat and it wouldn’t have to pull out at the first sign of any heavy air. And that concept meant that we weren’t particularly interested in the canting keel concept. I don’t think it is proven offshore, although a number of people say to me 'what about Open 60s?', but Open 60s aren’t sailed very hard and they tend to be sailed downwind. We looked at the Sydney-Hobart and said it is pretty normal for it to toss up a bit of on the wind work somewhere and normally it is southerly so it is cold, hard air and you get a bit of a hiding at some point and the whole idea of bow rudders and things like that leaping 20ft out of the water and crashing back down again - it didn’t seem like a sustainable option."

While Zana is what might be termed a conventional maxi Bakewell-White debates whether she is conservative. "I don’t think a boat this size is conservative. The loads are huge and the gear is all on the limit. The guys have to be careful..."

The design team looked at 30 different hull form and trialled these using the Woolfson Unit's VPP. "We looked at the tank testing and ultimately I said to Stuart that I didn’t think it was worth spending a lot of money on it because our decisions and basic parameters of the boat were going to have far more impact on the results we got rather than getting the nth degree out of one particular concept," says Bakewell-White. "It is a perfectly valid option for an America’s Cup or a Volvo where you are working in a box but essentially Stuart gave us pretty much a clean sheet of paper and said ‘come up with a boat that you think is going to get us to Hobart first'. So I thought that building models and going tank testing was really a waste of money."

Obviously a maxi was required for a line honours win but they then looked at whether an IRC maxi would be faster than one under IMS. At the time the former clearly won out, although Bakewell-White says that the gap has now closed since the CYCA have allowed water ballasted boats to compete under IMS.

Bakewell-White had carried out some development work on Ludde Ingvall's Nicorette and his team used a similar boat - an 80 footer with water ballast and a big rig - as their control against which other boats were compared. Over the course of their studies the length of the boat increased. "Surprisingly length doesn’t appear to be harshly treated under IRC whereas under previous rating rules, length is king and it has caused the most problems with people trying to cheat the length measurement with bumps, etc," says Bakewell-White. "I think long and slender boats are a healthy way to go because they achieve performance relatively easily and cheaply." The rig was also enlarged until they hit the rating limit and from there was a case of refinement.

The finished product has rounded sections forward and is flatter aft. "The hull is a nice, clean easy hull shape we’re not as flat and bilgy as a Reichel-Pugh boat like Alfa Romeo. We are a bit softer particularly up forward and that is keeping in mind pounding to windward in a seaway. So we are trying to keep the boat seakindly and keep the landings as soft as possible - if that is possible." In comparison Skandia have gone further down the reducing wetted surface area route and has more rounded sections aft. "That was a pretty important thing for us too getting rid of wetted surface," says Bakewell-White. "If a boat like this vulnerable in any way it is in lighter airs downwind and that goes for all boats of this size relative to smaller boats - they have less sail area and can be sticky in the light."

While the boat may not have a swing keel, it does have a trim tab on the keel and Bakewell-White is a big advocate of their use. "Anyone who has an IRC boat without a trim tab is mad. There is absolutely no rating adjustment for it and it has been known for years and years that they are an advancement. It is added complexity and a bit more expense, but it is free."

On Zana, the trim tab represents 20% of the cord of the keel. Previously Bakewell-White came up with a trim tab for Nicorette that was operated by a hydraulic ram similar to that of an autopilot. On Zana thanks to the influence of starting helm Cameron Appleton they have an America's Cup-type arrangement where the tab is operated by the helmsman from a smaller wheel within the main steering wheel. McConaghys have what is effectively an off-the-shelf system for this.

The keel foil itself is made of milled steel, while the tab is carbon fibre and the foil sections have been specially developed for use with the tab. Unusually the foil is not a pure foil share when the tab is at 0deg but becomes an asymmetric foil when the tab is used - which is almost all of the time. Upwind the tab dramatically increases lift improving VMG, while downwind it is effective in reducing the load on the helm (the trim tab also allows a smaller foil to be used reducing wetted surface area). "If the helm is getting loaded up on a shy reach you can wind a bit of tab on and it takes a bit of load off," says Bakewell-White. "You can steer the boat quite happily by just the tab. It is very effective even though it is right in the middle of the boat."

Zana's trim tab can articulate by +/- 12degrees and it also has tactical applications. "If you are coming off the start line and want to squeeze someone then you use more tab and go a bit slower and put the elevator on. And if you want to go into a faster mode you just reduce tab and just let her loose. We are lucky having Cameron on board because he’s got a lot of experience pre-starting in America’s Cup boats. They are using it to 12-15deg of tabs and using it almost like a break."

The cockpit layout has the standard twin wheels and a Harken winch package that includes five pedestials and three speed winches (here is another significant difference to Skandia which relies on electric winches instead of man power). These were derived from Harken's Cup work but have their titanium parts replaced with 174 stainless steel to improve their longevity. Like Bols, Zana has a central utility winch area at the forward end of the cockpit for all halyards, reefing lines, etc, each winch capable of being driven by all the pedestals (one is also electric). The only downside of the central winch arrangement is that it restricts the width of the companionway making it awkward for manhandling sails below.

"The hardest thing about sailing the boat is moving sails around because they are heavy and they are big," says Bakewell-White. "The first few weeks, you come off the boat and your fingers are aching and your forearms are sore just from pulling the sails around. But just sailing the boat is surprisingly easy."

Above deck the 38m tall carbon fibre spar was made by Southern Spars is similar in height to Alfa Romeo.

The present plan for Zana is for her to be taken out of her Rolex Sydney-Hobart mode and 'turboed' prior to being shipped to Europe. She will be fitted with a new bulb that is 3.5 tonnes lighter and will be able to make use of her ballast tanks that allow 5 tonnes of water to be pumped up to weather.

" Alfa Romeo has 6 tonnes of water each side, but our bulb is a bit heavier than hers," says Bakewell-White. "We’re relying a little bit more on conventional ballast, which is more effective at higher angles of heel. Water ballast is more effective at lower angle of heel, so there is a bit of a crossover there. Our choosing to run with less water is partly driven by our boat being 2ft narrower than Alfa Romeo."

At present Zana does not have an Alfa Romeo-style super fast tank filling system that uses of water jets. "We were going to go that high speed route the same as her but when we looked at the events the boat was going to do, we said ‘do we need to have that super high speed system?’," says Bakewell-White. "In the end we went back to a system which is more akin to a Volvo-type system with two big Pacer pumps. So instead of taking 20 seconds to fill, which is what they do on Alfa Romeo, we might take a minute and a half and 45 seconds to transfer. But the sort of races we are planning to do we are not planning on a lot of short tacking."

Saying this they did investigate the possibility of an improved version of Alfa Romeo's water jet system. The Alfa Romeo system jets water into the tanks and then uses the Venturi effect to expel it. The system can also be used to propel boat instead of a prop and incredibly the jet fills the tanks so quickly that it is believed to be faster to dump the water out of the boat, tack and then refill the tanks on the new tack than it is to simply dump the water down to leeward and then tack. Bakewell-White says they were looking at a system whereby they could also dump the water superfast using the water jet.

Zana arrived in Hobart 14 minutes short of Skandia. While this was a great disappointment to the team it was also a function of them not having been in the water long enough and still having teething problems to iron out. In particular they experienced a problem with their fitting for the deck fitting for the jib tack that was causing the tack to be torn out of all the headsails. As a result they were having to make headsail changes bearheaded, losing valuable miles every time a change was called.

"I'm happy that the boat is quick, but it just didn't come together," says Bakewell-White. "The fact is they kept coming back at them. If Skandia was faster she would have just sailed away. The crew said she was sailing a 0.5 knot faster at the finish than at the start. So it was too early on the learning curve really."

Zana is now back in Wellington, New Zealand where her owner plans to enter her in a number of local races and may attempt some record passages. The boat is likely to then head for Europe to take part in a number of the Rolex-sponsored events in the Med such as Giraglia race and the Maxi Worlds and also probably Cork Week. With Zana and the two new maxZ86s Pyewacket and Morning Glory threatening to attend, Cork Week is lining up to be one hell of a regatta this year. Ideally Zana would then be sold in Europe, otherwise she will return down under. In this case Stewart Thwaites and his team will be back on Boxing Day 2004 in the Rolex Sydney-Hobart to see if the tables can't be turned.

For more technical shots of Zana , see the following pages