Longtze: A blitz design story

Daniel Andrieu, member of China Team's design team, sent us this interesting report on the design of Longtze (Son of the Dragon), CHN-95, the first ever America's Cup yacht to be built in China. Given the very limited resources of the Chinese challenger, the design group was forced to attack the matter with a blitzkrieg, hence the title of the article.

Without any doubt, Longtze will be the boat in Port America's Cup not to need any unveiling ceremony because since his launch the Chinese team never tried to hide it:

Tomorrow, 1st of April, day of the "Unveiling Ceremony", will mark exactly one year, day for day, that Luc Gellusseau, Chief Operations Manager of China Team, summoned us, Hervé Devaux, Philippe Pallu de la Barrière and myself, and asked us to constitute the "China Design Team".

Goal: To design and have built the 1st Chinese ACC in history. Start of building in 3 months, the 1st of July, delivery on November 15, after 4½ months of construction in China.

The bet was crazy, we thus accepted it!

In a standard America's Cup campaign, the Design and Engineering Team is made up very early, generally from the very start, that is to say 2 to 3 years before the Louis Vuitton Cup. It is made up of multiple specialists allowing in investigation the whole definite design field. It has the experimental means (CFD, Tank testing and Wind tunnel) ad hoc. It works in coherence with the Sport Team. It takes part in the development of the ACC of old generations. It thus has the time and resources to conclude its task: design and develop a maximum of 2 boats, able to reach the highest possible level of the competition.

Our adventure was quite different from this ideal process.

The smallest budget of the Cup, approximately 10 million euros, dictated its harsh reality: No time, few human and technical resources, no referring crew, no research and development!

The specification book was at the same time simple and constraining: "You have three months to make us the best possible boat, you are completely free, with the "simple" following conditions:
1. The deck and structure of CHN-69 will be cut out and re-used for the new boat;
2. The appendages and rigging spars will be those of CHN-69"

In addition to myself, 4 America's Cups, China Design Team (CDT) is composed of two of the best specialists in the world in their respective fields, Hervé Devaux (HDS) for the structures, on his credit, 5 America's Cups, the large majority of the Open 60' and Multi 60', the winner of the last Volvo Ocean Race, etc..., both for the hull structures and the spars, and Philippe Pallu de la Barrière (CRAIN), 6 America's Cups, one of best in aerodynamics, hydrodynamics and CFD. This Design Team knows itself very well, having worked on many joint projects and is able to work in team, "without egos". Each one with his privileged field, but also intervening in that of the others, since after all, work is common.

First sail of Longtze (press play to start video)

Time is in extreme short supply for us: three months to start construction, which translates into 2 weeks to decide strategy, to choose and validate the CFD tools, to organize and distribute work, 2 months of design, then 15 days of work to pass from virtuality to reality. With such a short lapse of time, we quickly decide the total strategy of the project. It is necessary to limit ourselves to the essential, to follow without compromise only one main idea. The arbitrations or trade-offs, delivered in real time, must be limited to those based on our common experience, because we will have neither the time, nor the means, to undertake complementary studies and/or parallel investigations.

To try to go to essence in the balance of the boat, dynamic behavior, the control and sinking of volumes of overhangs, stability, structural stiffness and simplification, while remaining compatible with the old appendages, deck and rigging.

The very “boxy” form of "Longtze" is the consequence of these choices without any compromise.

The boat was built in Dongguan in south China, on male mold, for financial reasons but also in order to save time, adding a hundred kilos to the weight of the hull.

The trade off from the "plastic surgery" undergone by the deck and the structure to adapt them to the new hull was an additional hundred kilos on the hull.

During autumn, a new mast finally could be manufactured at Lorima, which limits the overweight of the spars to an old boom, and gave us a better sail power control than the old mast.

The bulb, going back to 2002 for an ACC of 25 tons, was re-cut to adapt to the displacement of "Longtze".

February 2007, "Longtze", the Son of the Dragon, made its first splashes in the waters of Valencia.

CHN-95 launched in the water for the first time. Valencia, 16 February 2007. Photo copyright Pierre Orphanidis / Valencia Sailing