The British wing

Bristol-based Invictus Challenge is back on the water and ready to contest this August's Little America's Cup

While BMW Oracle Racing may have been strutting around the 33rd America’s Cup race course with their 68.5m tall solid wing sail, in the UK another multihull with a solid wing has been taking shape – albeit on a rather more modest scale.

In 2004 Norman Wijker, and his co-workers from Airbus in Bristol who form the Invictus Challenge, made it across to the International C Class Catamaran Challenge in Bristol, Rhode Island. This event dates back to the 1960s when it was officially the International Catamaran Challenge Trophy (ICCT) but better known as the Little America's Cup. However, in 2002, the trustees of the ICCT abandoned the C-Class catamaran in favour of F18HTs, so the 2004 event was more a case of ICCT holder Steve Clark attempting to breath some life back into and C-Class racing the Little America’s Cup.

Since then the ICCCC/Little America's Cup (I believe we can call it that again now that ACM’s legal rottweilers are no more) was held again in Toronto in 2007 and prised off the American defenders by Canadian Fred Eaton. Now in August 2010 the event is to take place again, hosted this time at the ancient home of the BIG Americas Cup, New York Yacht Club in Newport, and the Brits will be back...

While BMW Oracle’s towering wing alone had an acreage of 600sqm, Invictus’s C-Class catamaran has an altogether more manageable 300sqft (27.87sqm) on its 25 by 14ft platform. The C-Class challenge is also quite different – 300sqft is the maximum sail area both upwind and down and bumping up the sail area with the addition of kites for the runs is prohibited. Therefore the challenge is beautifully pure and unique in the sailing world – simply to come up with the most powerful, efficient and manageable sail plan within the 300sqft box. As a result the rigs on the latest C-Class catamarans may be pint-sized compared to the enormous BMW Oracle wing, but relatively they are much more efficient.

The good news is that on their second challenge for the Cup, Invictus are tackling their Little America’s Cup campaign in a wholly new way. Their previous boat was unique in having a split flap (fore and aft) wing, but was dogged by reliability issues thanks to a lack of time on the water. This time they are taking a more conservative approach and have created their own interpretation of the triple element wing featured on Cogito and on the present defender’s cats.

“Since 2004 we have been trying to develop a new wing,” recounts Norman Wijker, who leads the Invictus Challenge. “It has been a gradual thing. We have been building this wing for a couple of years now, basically trying to catch up with the likes of Fred Eaton and Steve Clark. Odds are that we are not going to catch up with them this time, but we will definitely close the gap; but we are there to win and we may have a few surprises which we can pull out.”

With C-Class grandee Steve Clark keen to get the Little America’s Cup show back on the road, he and Duncan MacLane have been generous in providing technical details about Cogito’s solid wing sail, and this has benefitted the British team in putting theirs together.

Aside from SailRocket's Paul Larsen and Helena Darvelid, Team Invictus mostly comprises of Airbus employees – Wijker himself is a works in the Future Projects Office there, alongside Julien Chaussee who had a lot of the design input to the new wing. Construction of the Mk2 wing took place in the corner of a hangar at the Airbus facility just outside of Bristol, with the manufacturing spearheaded by GKN’s Phill Brown.

Sadly, Wijker says that they weren’t able to use some of Airbus’ state of the art composites facilities, however they were given access to some hi-tech wizardry thanks to EADS Innovation Works: “We have developed a titanium mast foot which was made by a selective laser sintering process.”

Aero design was largely carried out based on classical analysis rather than the computationally sophisticated CFD. This is largely because the parameters are easier to study and understand with simpler tools, while CFD is a fine honing tool, maintain Wijker.

The end result resembles Cogito’s wing in that it has three elements (the vertical components of the wing), with two slots and two flaps forming the rear element. Wijker compares it to Cogito’s wing: “We have a system which is basically a deformable trailing edge on element one. It is more a curved section than on Cogito in order to improve flow through the slot.”

However it has also been the source of teething problems, and they will be working on this in the run up to Augusts event.

Otherwise Wijker says: “There are subtle changes in the shape. Ours has got a curved leading edge on the top and the trailing edge is fully curved. You have to be a C-Class aficionado to spot the differences! There are subtle differences in the detail design – our control system works differently from Steve and Freds. The flap control system developed by Steve and copied to some extent by Fred – ie the A-frame that sits under the wing - we don’t have that. Our control system is internal to the wing and it runs up the back of the mast and we have a cascade system that takes the control lines up the mast and there we reduce the tension loads and then we bring them back down to the bottom for the crew to take hold of. We have a twist mechanism which again is subtly different to Steve’s but in principle it is the same.”

The main visual difference to Cogito and Fred Eaton's Alpha is the absence of the clear panels in the upper part of the front element. “This was experimental, the clear panels compromise the aerofoil shape, a solid skin should provide better aero,”says Wijkjer.

Invictus completed the new wing last summer and since then have been using it on their 2004 platform, which they reckon is still competitive.

Thanks to the motivation skills of Gordon Kaiser, who has been sailing the boat recently with Paul Larsen, they have been taking the boat out on the water down at Cardiff YC and Weymouth & Portland Sailing Academy at every possible opportunity. And compared to their 2004 attempt this really sums up the difference of their approach this time: they have a boat that they know is in the same ballpark as the competition and the emphasis now is to get it reliable, to learn how to sail it and do the utmost to optimise it.

“We want to turn up with something where we can put on a good show sailing wise,” says Paul Larsen. “We will be out gunned a little bit boat for boat, but if we can get it performing up at Cogito level and at least spend a hell of a lot of time on the water with it, we hope we can put on a decent show.”

At present for example during training and development sessions the boat has regularly proved to be a rocketship upwind – demolishing even Larsen’s potent A-Class cat, but has been suffering downwind. Wijker reckons that this is probably due to the deformable trailing edge on their front element. “That is partly down to the slot geometry and also we haven’t been playing too much with the element one twist so there are a couple of things there where we hope we can gain some boat speed. We also have some new daggerboards we haven’t tried yet.”

Already they are doing well (famous last words) in terms of reliability. As Wijker says: “We have had a spate of things breaking and trying to understand why they are breaking. We have got to the bottom of that now. I don’t think we have had any major breakages this year.” The primary weak link has been the lower flap which will be replaced with a new one prior to the event.

So far this year they haven’t broken anything and Paul Larsen provides an indication of where they are at: “We are twin trapezing on it now. It is going out with full load and it is tacking and gybing and spinning and twisting and cambering just like it should! We are sailing it downwind both to leeward with the hull flying, and getting quite confident with it now and it is behaving nicely.” This also applies to the difficult logistics of transporting and hoisting and lowering the wing - something they are now getting quite adept at.

Already the team are looking to the future and in reality, the team acknowledge that their latest boat is also a testbed for a potential race winner for the next Little America’s Cup. “Our first wing was just totally different and I think what we wanted to do this time is to try and get ourselves into the same ball park as Cogito and Alpha [Fred Eaton’s 2007 winner]. We are still working on our Mk3 wing, which will be quite different. We have got some ideas which we want to put into action on that,” says Wijker.

Over the course of this year they will be using their present set-up to gain as much hard information as they can, logging wind data and the input from load cells and strain gauges dotted around the boat, looking at how the wind passes around the wing and the flow around the bottom of the wing.

They also plan to up their game when it comes to the simulations next time: “We are hoping to develop the plan form optimisation a little bit more – so that the the taper and the flap chord ratios, etc will be evaluated as well as the flap setting process. We are going to try and simply the control lines, etc. At the moment it isn’t too complicated, but we believe we can synchronise the twist and the flat control,” says Wijker.

At present of course with the 33rd big America’s Cup having just happened and victory going to BMW Oracle Racing, solid wing sails are a talking point and this is likely to generate much interest in this year’s Little America’s Cup as well as the British challenger for it. Larsen describes how they have been received recently in Weymouth. “Kids come and look at it now and say ‘wow, that’s a wing’. So that’s a real strength.”

So will it be a goer? Larsen sums up the campaign: “There is a good foundation there. There are some good minds and some real passion. They have the trailers and the facilities and basic boat and the level it is at is a good starting point for anything to come out of the UK. Certainly we encourage anyone to come along and get involved on the understanding that there is not a lot of money there. It is still the only decent C-Class in Europe...”

He also believes they are in with a chance against the competition (more on them in due course) this August in Newport. “If we can spend more time on the water than anyone else and just keep refining the boat without compromising the amount of time we spend on the water we have to remember it is a boat race and I think we can put on a pretty good show on over there from a sailing perspective. We want to go and see the development in the class and keep the boat rolling. The fact is there will be a British boat there.”