New ‘Z’ board Cruiser-Racer Cat: The North Wind 55

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Gonzalo Redondo: The owner of North Wind Yachts, Enrique Ribot, called us for this project as he wanted a unique high performance catamaran. He had a great vision and put together a team composed of Francois Perus & Romain Scolari as naval architects, Jonas Hertwig responsible for interior and styling and Isonaval looking after systems and overall project? supervision. At D3 Applied Technologies we are responsible for performance, mainly hull and appendage design.

The NW55 has been developed as a high performance cruising catamaran which competitive owners could bring to regattas and be substantially faster than similar sized vessels.

– Which is the purpose of fitting this rather large Cruising cat with Z style boards and T rudders as seen in the render? Full flight or reducing wet surface skimming? 
GR: Funnily enough we faced the “remove appendages from the top” restriction, which is why I thought of Z-boards straight away. There will be two versions, one with standard C-boards and one with Z-boards as you see in the render. We are still developing the high performance package. I expect low-riding and skimming.

– Which a re the benefits of Z over curved then if full flight is not targeted a priori?

GR: Well, when it comes to the shape of the board, at the end Z boards are similar to the S boards used a few years ago. One nice benefit of Z boards is that you can unload the tips at the bottom. Also the exit from the hull is better, as you can make it 90 degrees.

Also, since the horizontal plane is more angled than C-boards you have the possibility to use the windward board to either create lift or increase righting moment as required. Since the windward board can be used to increase performance you do not pull it up, meaning the catamaran could be sailed short-handed as one could forget about the up-down system.

The main advantage of these Z foils is that in case of flying/jumping they have better heave stability than C foils. The biggest difference is dynamic stability and control… Some static VPPs might tell you that a C board with winglets are better.

– We’ve seen how winglets reduced pitching even in the A-Class flaoting mode, so besides the skimming we can say winglets are also a safe asset for the 55?GR: Totally, they will be offered as standard in both configurations. Cruising and comfort go together, as do racing and control, so there is no reason not to include them. However, and this is something we are investigating in the A-Class, the foil sections at the winglets we are using are no longer symmetrical. Flight dynamics are very interesting in this respect. The A-Class winglets are now asymmetrical so there is a bit of a tandem wing configuration on them. On the other hand, the kitefoil elevators we are designing are also asymmetrical but in this case the section is upside down, creating a bow up attitude which is what riders can control.

– We’ve seen the smaller & lighter 40′ G4 foiling good with TNZ 3pt foil system, can we expect the A-Cat type 4pt you guys are using in this NW 55 , to be efficient for full flights on a similar platform like the G4? Does NW has plans for smaller versions?GR: Yes, 4pt configurations can fly efficiently with the right controls.
We have not talked about newer/smaller versions but if this project is well received I am sure North Wind will be keen.

– The 4pt Z board is now being adopted in the Nacra 15, surely i nthe N17, you have designed latest Exploder foils and you have also worked in Americas Cup projects,
is there a chance to see the 4pt in coming AC for Bermuda?GR: No. Rule 11.14 says the windward board cannot be used to increase righting moment. This lack of righting moment is what makes the current 3pt configuration better than the current 4pt configurations. I would emphasise “current”.

– What about the board raise system, curved boards seems to have a smoother framework, and Z as seen in the As do have a special space required in the deck for fully raised?
The boards will end flat over the deck?
GR: We have designed the tightest daggerboard trunk possible, so the way they are positioned is not a problem even for the interior. They do go a bit over the deck but this is something we studied and is not a problem. In the end when sailing, both boards will be down.