Sail-World.com : Pioneering integrated performance development
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Pioneering integrated performance development |
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'Fiat'
Frank Quealey © /Australian 18 Footers League
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Going into the 18-foot skiff World Championship, the JJ Giltinan Shield, on Sydney Harbour this weekend three of the competing skiffs carry pioneering integrated sail and spar technology developed by the North Sails group.
The further development of North’s 3DL sail production technology and a relatively new partnership with spar-maker Southern Spars gives these skiffs a significant advantage over their fleet rivals.
Two years ago North Sails Australia, led by managing director and ex-18-foot skiff sailor Michael Coxon, saw the opportunity of applying 3Dr sails and North’s Flow and MemBrain computer program to the next phase of 18-foot skiff development.
The technology is not new. It has been well-tested on a range of large yachts by some of the best sail-designer minds. The difference for Coxon and his team is the application of that technology on significantly smaller, but still high-performance boat.
Where did it all start ?
The modern America’s Cup rule has always encouraged big roach mainsails and as materials and technology have advanced in both spars and sails, North Sails has lead the development of big-top sails. The lessons learnt from successive America’s Cup were then applied to maxi yachts such as Alfa Romeo and Wild Oats XI, as well as Volvo Race boats.
 | Alfa Romeo has already been a beneficary of integrated performance development - North Sails |
The North sail-designers found big-top mainsails on ridged masts had a nice twist profile, automatically controlling power as they go up and down the wind range, rather than as traditionally found on a skiff with a relatively soft mast where the mainsail relies on the mast to do the work and the sail to follow behind.
The designers also found on these yachts that the stiffer the mast, the more control they had over the sail and the more the sail worked for them. This concept was then taken into the maxi yachts. Again, they found the stiffer they made the masts in the maxi yachts, the more successful the big-roach mainsail was, as they searched for stability in the sail and in the mast. Achieving stability meant the large roach mainsail could do its work.
Another interesting lesson from the big boat programs was that the bigger roach sails reduced rudder angles for weather helm on the yachts.
'Basically, by putting more area up high, most people would think that was aft of the centre of effort of the rig and you would end up increasing weather helm. But, because of the trip profile working automatically, it actually decreases helm. We found with the pin-head mainsail the rudder angles are up around the five to six degrees. When we put the big-roach mainsail on, we reduced down to about three degrees.
'Less rudder angle means less drag so you get better performance,' Coxon explained.
This was another factor that Coxon considered a potential positive for the 18s.
Pioneering 18 footer development
With these lessons under their belt and a long-held passion for 18-foot skiff sailing, Coxon embarked in 2006 on a development program with two boats – Fiat (Michael Coxon, the nephew of North’s Michael Coxon) and Gotta Love it 7 (Seve Jarvin).
The development program started with the crews making changes to their carbon 18 footer rigs to make them stiffer. Previously the 18s raced with aluminium rigs with a luff curve of about 550 to 600mm. Changing to carbon rigs, five years ago, reduced the luff curve down to about 480mm but did not really change the characteristics of the boat and how it was sailed.
The rig changes during the 2006/07 season were achieved through changing from an aluminium track to a carbon track right the way through the rig. The new carbon track increased the stiffness of the rig by around 12 to 13 per cent. They also cut off parts of the tapered section of the rig leaving a fatter section. Both of these innovations gave them a rig about 20 per cent stiffer than the boats had previously.
It was the first major step in improving the performance of the boats.
The North Sails team then introduced the two skippers to 3Dr sails. 'Their boats require very durable sails that hold their shape for a long period of time because the club owns all the boats and all the sails. So, what they don’t want to be doing is replacing sails every year. The 3Dr product is ideal as it has very, very good longevity both in strength and in holding its design shape where panel sails tend to lose their design shape fairly quickly,' Coxon said.
As you could imagine, skiff sailors are tough on sails which includes high impact during swims. With 3Dr now in its second season on 18ft skiffs, North Sails have not had a sail failure.
'The sails are so much lighter than any panel equivalent. Which is a big saving to the boats and the crews, as we know, dead weight slows you up.'
3Dr has been in the development phase for the last ten years. It is a derivative of the 3DL North Sails technology that took the sailing world by storm 15 years ago.
The 3Dr sails are moulded on a rotating drum. The sail is formed over the drum as it moulds into the sails shape, as it goes over the drum, it is moulded and cured instantly. This method of production allows for more than one sail of a similar denier, or yarn weight, to be moulded at one time. North’s can now produce a larger number of thermo-moulded sails quickly and cost-effectively.
'Whenever you look at a moulded 3Dr sail, the leech twist is just beautiful. It is really, really fair. Getting the fair leech twist is one of the key parts to getting the boats performing on the water,' Coxon said.
Both Fiat and Gotta Love it 7 carried these new sails in the 2006/07 season. As a result of the two-boat development program they dominated the results during that season, and finished first and second, respectively, in the 2007 World Championships. 'The two boats were considered to be quite a step above everything else,' Coxon said.
Coxon at this point was simply not willing to let the development program come to an end without utilising North’s then newly-available Flow and MemBrain program. With the support of Fiat sponsor Neville Crichton and Gotta Love it 7 sponsorship manager Iain Murray, Coxon put the boats back on the water for a winter of intensive development and testing work under the guidance of 7’s coach Andrew Palfrey and Coxon.
'Over the winter months between April through to June last year (2007) we decided to leave 7 as standard, which had the first step towards a stiffer rig, but make modifications to Fiat on their number one rig. We then took the 06/07 Fiat mast, which was identical to 7’s 06/07 rig, and started to wrap carbon around it.
'We thought it looked good, but could go some more. We ended up stiffening it quite a bit to reduce mast bend significantly again,' Coxon said.
They re-cut the Fiat mainsail putting a new luff curve onto it and increased the roach. 'We knew we could push the roach larger as we got stiffer, so we went out over winter and did extensive testing of this. The feeling was we were going in the right direction.
'We would go off Sydney heads and Palm Beach for hours where in winter you can get nice flat seas and constant winds. Our conclusion at the end of this testing period; the rig was not only competitive going to windward, it also was faster downwind.'
These testing outcomes led the development team to sign off on the sails, but then pursue further development of the rigs.
Southern Spars, a member of the North Marine Group, was asked to look at the 18 footer project. Their one-design expert John Clinton sat down with North’s sail designer, Keith Lorenz. A set of parameters were established and the team of Clinton and Lorenz went to work on designing a new rig.
This approach to sail and rig design is an innovation of the North Sails group utilising a very powerful computer program which gives the sail designer the power to analyse the rig and the sail together in the computer before the boat actually goes sailing. Fully-tested through America’s Cup campaigns, the program has been available for use in North Sail lofts for the last 18 months and is now used as their standard tool for day-to-day sail design work.
 | Gotta Love it 7 - Frank Quealey © /Australian 18 Footers League |
There are two key elements to the program - Flow and MemBrain. Flow analyses loads produced in sails within a pressure map. MemBrain uses the pressure map to analyse how the sail/rig combination reacts to external loads.
Flow and MemBrain marries both the sails and the spars together. The designer uses the program to create a virtual rig in the computer. They put in all the measurements of the rig. The program then creates a rig on top of the boat in the computer with all the correct rig characteristics. The next step for the designer is to put in all the details of the sail.
Then effectively the designer can fly a sail on that rig on the computer. It shows how the sail is going to set, its shape, its twist, how the mast is bending and how all the elements will interact.
Coxon and his team were able to build the sails without actually measuring the masts. 'We trusted the computer program. All the luff curves were done just as if you we were doing yacht sails, with computer generated numbers. They came out very, very close to the mark. We had to do a little bit of fine-tuning and then we were out testing it.
'One of the most important factors here is the 3Dr sails. The 3Dr sails allowed us to bring the newest sail technology onto the 18 footers, which have always carried traditional panel sails.
'We can make lighter sails and we can reproduce the design shape exactly,' Coxon said.
The other important factor has been the consistency of the Southern Spars product. They have been able to produce within 2 or 3mm of what are the design requirements. This consistency in the product has given the North’s team the confidence not to bother re-measuring between one 18 footer rig and the next.
'As with grand prix yachts, we design the mainsail luff curve to achieve the optimum rig range then tune the rig around the sail template.'
Clinton gave the North team a number of alternatives based on what the team considered their priorities; to save on windage, to save in weight or to go to one extreme or the other. With the class rule measuring the overall ready-to-sail weight including hull, foils, rig and sails, Iain Murray felt strongly that with the savings in 3Dr sail weight, the designers could pass this saving into the rig and pursue a smaller section to reduce windage.
Murray’s justification was, unlike yachts which average 24 degrees heel angle, skiffs sail dead flat to windward so this will not adversely affect righting moment. As it turned out the masts were no heavier than the previous larger and softer sections.
The team also looked at the effect on sail design of the fore and aft, and side-ways mast bend. By marrying these two together before they built the spar they were able to re-engineer the mast to reduce the side-ways bend.
In engineering the mast the designers also looked at the rigging. With rigging being manufactured in different weights and stretch characteristics, the Flow and MemBrain program helped to determine the rigging size needed on the 18 footer to achieve the mast set up the sail designer wanted.
'You find, by the sail designer and the spar designer working together, they can optimise the sail shape, rig and rigging weight, and minimise windage.'
Does the integrated mast/sail combination work for high performances racers ?
The first Southern Spar rig and 3Dr mainsail produced out of this phase of integrated design program was for Fiat. The team conducted extensive testing of the Fiat mast/sail combination against Gotta Love it 7’s older mast/sail combination.
'When we first launched them there were times when both rigs were faster than each other. In other words, the standard rig was at times faster than the new, more radical rig. However, we could see the potential there.
'It was a whole new ball game in terms of tuning these rigs. As we got a better handle on that we realised the potential of the new rig was there. So 7 came on board and built an identical rig to Fiat'.
Macquarie Real Estate (Micah Lane) also races with a Southern Spar rig and 3Dr sails designed by their coach, Euan McNicol, in conjunction with North’s designer Keith Lorenz and Southern Spars designer John Clinton. As the current International 14 class world champion Euan wanted to experiment with a slightly different development path; with a rig set up more in line with the 14s, which eliminates one of the traditional sets of diagonal rigging standard on 18 footers today.
'Macquarie Banks recent results suggest he may well be onto a good thing' Coxon said.
 | Fiat - Frank Quealey © /Australian 18 Footers League |
Gotta Love it 7, Fiat and Macquarie Real Estate were the top three boats at the recent 2008 national championship. Another North 3Dr team member, Club Marine (Adam Beashel) was placed fifth.
On the water last week, many of the fleet were training in preparation for the World Championship. 'Fiat and 7 appeared to be the pace-setters out there. The world’s competitors would have come in from training saying there is no question, those two boats are the ones to beat,' Coxon said.
The Flow and MemBrain program can be used on any rig. It really is a case of getting the right data out of the rig manufacturer.
'The thing we tend to find more difficult is other (spar) manufacturers are not familiar with providing the data our designers require, so we have to fill in some of the spaces with best judgement. If the input numbers are accurate, it can be applied to any rig.'
The 18 Footers Giltinan International Championship is being contested on Sydney Harbour starting this weekend and going through to 24th February. Twenty-nine boats from four countries will be contesting the event.
by Tracey Johnstone
1:56 AM Sat 16 Feb 2008 GMT
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