Botin Carkeek Yacht Design
Tuesday, 30 September 2008 11:10:17
What was the biggest challenge you faced in coming up with the design for the second generation Volvo Open 70?
The biggest challenge was to adapt our tools to a design that was very different from anything that we had done before. Even standard tank testing methodology is inadequate for dealing with these much wider and faster boats.
Computational Fluid Dynamics (CFD) validation data had to be re-examined and part of our tank testing program was dedicated to making sure that we were getting good results from the computers.
Adapting the Velocity Prediction Programme (VPP) to such a wide range of sailing conditions was another huge challenge. In the America’s Cup, for example, you just need to worry about modeling upwind and downwind sails through a wind range expanding from 6 to 20 knots. In the Volvo you need to model sails for all wind directions and wind speeds up to 35 knots.
The second biggest challenge was doing this in a very short time span. In order to get as many tank models tested as possible we had a model builder working full time just under our office. The process turned out to be very efficient. Soon he was producing fully finished carbon models in a few days. We still had to produce the designs for the new generation models before we had results from the previous session which is not always ideal.
How much different are the boats from their predecessors and in what areas?
In the last Volvo race there were two distinct families of boats, represented, by the ABN AMRO boats on one side and by all the rest on the other. The obvious differences between these two families, was that the first had more stability, especially ABN AMRO ONE, and had two rudders instead of one.
This time around all the boats are very different from the single rudder generation of boats but in broad terms they are similar, philosophically, to the wider, more stable ABN AMRO ONE design.
Obviously there are many differences between the new boats but they all seem to follow the trend towards high stability, powerful hull shapes which proved to be successful in the last race.
What specific learnings did you take from the 2005-06 race in terms of design, upwind and downwind performance?
It became quite obvious from the last race that stability paid handsomely even at quite low wind speeds.
On the other hand, this time we had to deal with a very different route, with a lot of upwind sailing in various wind speeds, so the goal posts have moved and it will be interesting to see which is the best all-round solution.
From a structural point of view, it’s obvious to say that a boat that breaks doesn’t win the race. On the other hand, the performance of these boats is such that you get to a point where the crew needs to judge the risk involved in pushing the boat to its structural limits. The limiting factor is not how much the crew can push the boat but how much the boat can resist without failure.
How long did the entire design process take and what were the crucial stages along the way?
Ultimately, the final hull lines had to be produced in approximately four moths. The design team had to be quite creative to make the most out of the short time available.
A designer will always say he wants more time to refine the design. The truth is that once you work towards a given deadline the whole process seems to automatically adapt to that time span and sometimes you wonder whether more time would make a significant difference.
What I can say is that the whole design team has made a great effort to produce the best possible design in the time available. We’ve had enough time to do what we wanted to do and lack of time will not be an excuse if the boat doesn’t perform as expected.
Where have you sought to optimise performance gains?
Essentially through hull shape and appendage optimization with the objective of finding the best all-round solution. This process is always closely linked to the choice of beam and stability. If you get this right then there is a good chance you will be in the ball park in terms of performance.
Obviously, there are many other aspects of the design which are very important. Sails will probably stand as one of the most important items together with the mast and general aero optimization.
Finally, refining the structure to achieve minimum weight with the maximum allowed keel and bulb weight was certainly a challenge.
What is your view on some of the innovations which the second generation boats feature such as the pronounced spray rails on the Russian boat?
I think they are interesting design features that will probably work better on boats slightly different from ours. I don’t think they are beneficial in all conditions so it’s a matter of deciding whether they fit the performance profile of the boat that you want to produce.
In what specific areas has the new course influenced your design?
Appendage design was greatly influenced by the race course. The fact that these boats had to go upwind efficiently had very substantial effects in the configuration, positioning and philosophy of our appendage package.
What do you expect the second generation boats to produce in terms of performance?
We expect the new generation boats to be better all round. Upwind and close reaching they will be much better.
Is a 600-mile 24 hour record on the cards in this race?
Maybe we would have designed a very different boat had that been the only objective.
How do you see the race panning out over the course of the 37,000 miles?
It’s hard to anticipate how things are going to unfold. I think the sailing conditions are very different on each leg and therefore some boats will be better in some stages and worse in others. We may find that the best all-round boat is not the best boat in any of the legs.
This is certainly the case in some of the computer models that we were running and it could turn out to be the case in the actual race. So I would say the team needs to be patient and consistent and aim at getting good overall results in all the different stages of the race.