Antoine Koch Paprec Arkéa pour Tip & Shaft

Antoine Koch decodes the new Imoca Paprec Arkéa

Paprec Arkéa will be launched on February 22 in Lorient. It was designed by Antoine Koch and the Finot-Conq studio as was the new Imoca for Thomas Ruyant, launched in March. And so this is a timely opportunity for Tip & Shaft to discuss with the engineer/architect Koch.  

Can you tell us about the genesis of this Imoca project? 
On the first Imoca for Thomas (Ruyant), the team had really wanted to minimize risk by choosing what was considered best at that time, namely Guillaume (Verdier). I then worked with them to try to optimise the boat a little more for downwind. You’ll see that Thomas likes to do his own thing. That shows in his way of managing his team, of telling his story with his partners, but also when sailing. So he wanted us to put together a design team to deliver a different vision.

► How did this design team come together? 
It so happens that I did my end-of-studies internship at Finot-Conq during the Vendée Globe 2000. And really I had maintained very good relations with Pascal (Conq) and always kept in the back of my mind the possibility of working with them sometime. Even if they have not been so prominent in races in recent years, they have a very broad know-how on the whole design of a boat. In particular David de Prémorel, the real linchpin of the firm, who is very good on the structure from the beginning to the end. I liked working with someone capable of doing structural checks but also having the global vision of a naval architect. And from the outset we also planned to call in GSea Design for structural calculations and drawing. There was a good overlap of skills and ideas between us.  Finot also have the CFD facility, especially for the digitization of flows, one of David de Prémorel’s passions, while for my part I was more into the VPP side, the dynamic simulator and appendages. When I say “on my part”, I include Bobby Kleinschmidt, in charge of designing the hulls and appendages at Team New Zealand. We worked with him and David on the hull. Guénolé Bernard, who is at Luna Rossa for a long time did all the foil and rudder systems, and a young guy, Thomas Dalmas, who came from the Initiatives Cœur design office, was very helpful in doing all the background work data analysis.

► When did the Paprec Arkéa project join your mix?  
Even before we had finalized everything with Thomas’ team, we knew that a new Paprec Arkéa team was being set up. And so we spoke with them fairly early. But they waited to choose their skipper before finalizing things with us because it was a fundamental that he was totally on board with our thinking. It turns out that Yoann (Richomme) also had a strong historical relationship with Finot-Conq. He he had liked the way the firm had responded to the Figaro class call for tenders for the Figaro 3. Yoann was also reassured by the presence of GSea Design and by the fact that I have sailed in the Imocas a bit so he validated the collaboration.



“We chose a narrower boat” 


► What was the starting point for designing this boat? 
We started from the observation, shared by everyone, that the boats were very uncomfortable and hard to use on a round the world race. We saw in the last Vendée Globe that downwind in rough seas, they had trouble getting through the bigger seas and there was very uneven speeds, constantly going from 15 to 30 knots, and vice versa. That is exhausting for the skipper and does not produce high average speeds. We know, for example, that Thomas’ first boat (LinkedOut) is very efficient, but requires a very high work rate and effort that is not easy to sustain or manage. We can see it very well in Molécule’s film [29 173 NM, currently presented at the Sailorz Film Festival, Editor’s note]. It is a good insight, where to start putting ideas in place on the commitment required by the Vendée Globe and the boat, certain images are impressive.

► And what are the key answers, what were your fundamental choices? 
Overall we decided to make a narrower boat than the generation before. We see that this is a common choice now as we saw with Charal, I expect Guillaume (Verdier) to also take a step in this direction for the new Apivia. Then, to improve performance downwind, we tried to reduce the wetted surface quite a bit. Here we see we are quite different from Charal, which has very U-shaped sections where ours are more V-shaped, which sets the boat a little more for low heeling angles and which should make it a little easier to manage downwind, to slide along better and with less pronounced ‘relaunch’ angles. Today, the current boats, downwind, are quite binary. On Thoma’s boat if you bear away and sail deeper suddenly you’re down at 15 knots, which is too slow, but if you luff up in the same breeze you’re at 25 or even 30, and straight away it is difficult to manage, there is really no in-between. With less wet surface, we hope to have a more linear behaviour. We chose to have a scow which, at the level of the bilge, looks very like Charal, except that below that, we have a small, fairly slender bow which is there to dampen movement. Really, though, everyone talks a lot about the bow because it’s what is most visible, but the stern is just as important to pass through the waves. So we worked a lot on that, I think we are a little wider in the middle and narrower at the back than Charal, the objective is to reduce the drag and allow the boat to sit up more downwind when we need it, but also to move well in the waves upwind.

► And if you compare it to Malizia-Seaexplorer, Boris Herrmann’s VPLP design? 
We are probably closer to Charal than Boris’ boat which is wider. The common point with Malizia is the quest for a small wetted surface to be able to sail flatter and be optimised more for downwind. On the other hand, the keel line is different and he has more rocker than us, which probably makes him a bit more set up for the breeze. What is interesting is that we have all worked on the same theme, but we get to proposals that certainly have common points, but also big differences.



 “Totally different answers when it comes
to the deck plans” 


► Are the boats of Yoann and Thomas the same? 
The two teams decided on the points where they were going to do the same thing, like the hulls and the appendages are also close. On the other hand, for the deck plans and ergonomics, everyone came up with their own ideas. Naturally there is a divergence. It is interesting to note that we both have totally different answers to the problem of having to move as little as possible in the living area. You will soon see…..

► What performance differences can be expected between Thomas’ first boat and the new one? 
We must be careful not to draw quick conclusions because the decisions taken to improve the behaviour and handling of the boat in the sea mean that in some other conditions they can slow it down. It is quite likely, for example, that during training in the bay of Port-la-Forêt, on flat seas in 15 knots of wind, the new ones will be slower than the “old ones”. On the other hand, as soon as there are strong winds and seas, and in particular downwind, which is usually the case on a round the world race it should go faster. Beyond that it’s not easy to quantify. But for example, if we compare the fifty or so hulls that we tested with a reference very close to Thomas’s boat, there may be differences in drags of around ten percent on a wave cycle of 4 seconds in favour of the new hull. And at the peak of the drag, when the boat buries its nose in the water, we have a more than 50% gain with the new boat. Admittedly that’s for a very short time, say half a second, but this half a second is enough to slow the boat, which then requires more energy to relaunch. We think that all the instability in speed that we see today is caused by this very strong drag peak and here the gain is still relatively significant. If it happens as we have seen in simulation, we can expect a boat that will slow down much less in the waves and will potentially deliver higher average speeds.

► Now that all the major choices have been made, what’s next for the programme? 
We will accompany the teams until the Vendée Globe, which really is going to roll around very quickly. It is not about delivering a finished product when it is launched, it’s like an F1 car, you have to update and optimise it over the season. We are already thinking about changes, I try to keep an open mind always as an architect, we will take what works best.

Photo: polaRYSE

Tip & Shaft est le média
expert de la voile de compétition

Course au large

Tip & Shaft décrypte la voile de compétition chaque vendredi, par email :

  • Des articles de fond et des enquêtes exclusives
  • Des interviews en profondeur
  • La rubrique Mercato : l’actu business de la semaine
  • Les résultats complets des courses
  • Des liens vers les meilleurs articles de la presse française et étrangère
* champs obligatoires

🇬🇧 Want to join the international version? Click here 🇬🇧