Design- The ‘power package’ of ABN AMRO's

by Andy Rice, Sailing Intelligence on 9 Dec 2005 As leg one has shown, there are significant differences between the design of the Bruce Farr boats and the ABN AMRO boats, designed by Juan Kouyoumdjian. Each design has its advantages and disadvantages in different weather. Here Juan talks about why he made the decisions he did with the ABN AMRO ONE and TWO.

Rudders
One of the most fundamental distinctions between the boats is in the choice of one rudder or two. The Farr boats employ one, while Sunergy and the ABN AMRO boats use two. It’s the first time the twin-rudder configuration has appeared in the 32-year history of the Whitbread/Volvo Ocean Race, although they have been de rigeur in other modes of round-the-world racing for some time. ‘They’ve been used in Open 60s for almost 15 years now. We looked at different appendage considerations very early in the programme. It was one of the first decisions made on the programme that we needed two rudders. I think that was decided back in February or March 2004.

‘Having twin rudders gives you a heck of a lot of control’, says Juan. ‘These boats are sailing with apparent wind angles of 40 to 60 degrees most of the time, and downwind on VMG angles they go to 70 or 75 degrees of apparent wind angle, but no more than that. So call it 80 degrees at the very, very widest. So they’re always sailing with apparent wind angles that effectively mean the boat is sailing upwind almost all the time. This means the boats are heeling over all the time, even when they’re in VMG mode downwind, and so having control when the boat is constantly heeled requires you to have two rudders, with the leeward rudder doing all the work.

‘When you put all these things together you can reduce the size of the rudders so much for the same level of efficiency as one rudder, that you end up achieving similar levels of drag. It was clear as water that rudder drag was not an issue. In any case, the extra control that having two rudders brings is easily worth any drag factor that goes with that. When the boat is heeled you don’t add any drag, because the other rudder is out of the water’.

The option of two rudders also allowed to Kouyoumdjian to develop the broad, powerful hull shape that he felt was appropriate for the Volvo Open 70. ‘The moment you decide that you’re only going to have one rudder, you are locked in, your back is against the wall, as far as the hull shape you can do. You can see this in the Farr boats a lot, that they are designed around the fact that the boat has only one rudder. There is a direct link of the dual-rudder hull shape compared with the single-rudder hull shape. With a hull shape like the ABN boats, you could not have one rudder. In fact with that hull shape you would lose control all the time, so the fact that you have two rudders allows you to have a much wider and efficient hull shape’.

Far from radical
Kouyoumdjian has always been known as a bit of a free-thinker and a radical in the world of yacht design, while Bruce Farr has been the benchmark designer for over 20 years, the designer against which all others are measured. However, the Argentine designer believes his creations for ABN AMRO to be far from radical. ‘I think of them as being quite conservative. In fact, when we came to conclusions about how to design the first boat, I was tempted to do something a lot wider, but common sense told us to take a more a conservative approach. If I were to do another Volvo 70 now, it would be quite a bit different’.

Whereas in the last Volvo Ocean Race, the difference in beam measurement between the VO60s was a matter of a few millimetres, the variation in beam measurement of the VO70s is hundreds of millimetres difference. Kouyoumdjian says the Farr boats are the narrowest, at just over five metres wide, whereas he believes the broadest hull to be Sunergy. The ABN AMRO boats are at the broad end of the spectrum, with ABN AMRO TWO around 5.45 metres and ABN AMRO ONE a touch wider at 5.6 metres.

Spinnaker poles
One of the other clear distinctions in the fleet is between those who have a spinnaker pole and those who don’t. The Pirates of the Caribbean is the only Farr boat not to have a pole, along with Sunergy and the ABN AMRO sisterships. The VO70 rule is very strict about the maximum all-up weight of the boat, so any deck gear that can be dispensed with can be translated into additional weight into the lead bulb. Mike Sanderson reckons that by dispensing with the spinnaker pole and all its associated deck gear, he has been able to put another 75 kg into the bulb. ‘We’ve gone for the full horsepower package, and I don’t see why you would want anything else,’ said Sanderson before the start in Vigo.

Then again, movistar had done 20,000 sea miles and felt confident that the spinnaker pole was giving them options to sail different angles downwind in certain conditions. Kouyoumdjian remains unconvinced by this argument, and stands by the decision to go without a spinnaker pole. ‘I don’t see it as a compromise at all. For me it is as clear as water. Mike Sanderson also came into the team with the same view. For us it was a no-brainer. We hardly studied it because it was so obvious to us.

‘I don’t agree with anyone who believes they have an advantage with a spinnaker pole in anything less than 25 knots. OK, it is true that in 25 knots of wind speed and above that the spinnaker pole could bring an advantage, but I think in those sorts of winds you’re going to have much bigger issues than a few degrees of pole, you know? Having the pole in those conditions may help stabilise the boat and keeps the bow up a little bit more, but that only happens with a big spinnaker, and I think you’d be crazy to have a big spinnaker up in more than 25 knots. At that stage you’re already on the fractional spinnaker, which does most of the work of a spinnaker pole in any case’.

The power package
Of course the race is still young and it remains to be seen what the weather will bring around the planet this time. Medium to strong breezes should continue to favour the ABN AMRO ‘power package’, but if the wind drops light then the Farr-designed boats will be very slippery. For two designers that have come to two such different conclusions about the VO70 rule, it is interesting that Bruce Farr and Kouyoumdjian also happen to work closely together on another project, the BMW Oracle Racing campaign for the America’s Cup. This has given Kouyoumdjian an opportunity to watch the acknowledged master at work. ‘I respect Bruce a lot. I think he is a brilliant guy. The attention to detail and the level of refinement that he goes into is quite admirable.

‘I’ve learned a lot there, and it has influenced me to try and achieve the same level of detail or refinement when I do my own designs. So far I’ve been more of a big picture kind of guy, trying to get the fundamentals right. In trying to get those right, you always run out of time or run out of budget to go further into the details. Bruce is very conscious on getting every single little detail right. In that respect we are a little bit different, but for sure I have learned from him, and we are applying that approach to our future projects’.

TEAM ABN AMRO Website: http://www.abnamro.com/team