Volvo Open 70 – Version 2.0
With their high freeboards, voluminous angular hull sections and towering rigs, Volvo Open 70s remain imposing, aggressive and intimidating on the dock, just like their earlier sisterships.
At first it is difficult to see just what has changed from the first iteration of the VOR class rule. Yet dig a little deeper and it becomes clear that the boats that make up the new fleet are highly-refined and substantially more powerful.
Here, two main areas have driven the development in this class, changes in the rule itself and the greed for more speed.
VO70 – The New Rule
When it came to performance, the first breed of new VO70s for the 2005-06 race proved that they had raised the bar for offshore racing. By the finish, no one was complaining about their performance, at least not when it came to outright straight line speed.
So, in reviewing the rules that govern the design and construction of these boats, the focus was on refinement rather than radical changes. Understanding the loads that these powerful machines generated downwind was one of the areas that focussed attention.
In an effort to encourage designers to put more structure into the boat to improve reliability and durability the range of acceptable displacements was reduced to 13.86-14.00 tonnes, while a maximum keel bulb weight of 7.4 tonnes was also set.
The rules governing the appendages was another area to be tweaked with two dagger boards and one or two rudders the only options permitted, while the troublesome bomb doors and moveable fairing systems around the keel/hull interface were outlawed.
Above deck, all spinnakers are now allowed to be furled, and spinnaker poles are banned, moves that will help make the sail plans more manageable for the crew as well as reducing development costs. Another change in the rig package is that an additional masthead spinnaker, the so called code zero, is now permitted to improve light airs performance.
Another big change above decks is that non-metallic standing rigging is now allowed throughout. This move reduces the overall weight of the rig dramatically. The lighter rig weight will improve performance significantly by reducing the weight aloft and reducing the pitching moment, which in turn will reduce slamming.
VO70 – The New Boats
When it comes to developing power, beam is one of the fundamental keys. More beam means more righting moment, albeit with the penalty of greater drag.
With the fin and bulb configuration now fixed at 7.4 tonnes and a maximum draft of 4.5m, there is less flexibility in the range of righting moments that can be generated from the fin and keel system alone making the waterline beam of the boat more significant. Hence, the righting moment versus the beam and wetted surface area lies at the heart of these boats’ design.
As always, hull shape is another important issue.
“Flat runs aft help promote planing but also tend to keep the bow down, making it more difficult to steer at speed,” said Russell Bowler, of Farr Yacht Design, who designed both Telefonica boats.
Getting the balance of performance both upwind and down is another important issue as Shaun Carkeek of Botin Carkeek, designers for the PUMA boat, il mostro, explained.
“The percentage of time spent reaching will be around the same as before, but some of the time spent running will now be traded for upwind work,” Carkeek said.
“Last time around we saw glimpses of what’s achievable through different hull shapes. We also saw how important the balance between righting moment and light weather performance is. But we believe that while these aspects are very important, understanding the aerodynamics of these boats will be crucial.”
Here, the development in the rigs is perhaps the easiest to identify at the dockside. With boat speeds that are rarely out of double figures and apparent wind angles that are rarely aft of the beam, windage and the drag that results has become more important.
Consequently rigs are much cleaner than previously with lower drag rigging attachments and sheave cages along with a more considered layout of halyard exits to reduce drag in the all important slot.
Rigs can now be built using high modulus carbon fibre which means stiffer rigs that can be smaller in section at the top to reduce windage further, although there has been a balancing act to perform here with the higher topmast loads associated with the masthead upwind genoas.
Opting for the non-metallic rigging route has been a no-brainer for the teams this time around, the substantial weight savings that have been gained here have not only contributed to a better all round motion for the boats, but have allowed designers to specify a heavier, more robust spar that can carry the additional loads.
When it comes to sail plans and wardrobes, teams have had to completely re-think their armoury. No longer the Southern Ocean sleigh ride once the corner at Cape Town is turned, the fleet now has to step into completely new territory with the potential for long upwind legs, especially the 2,500 miles from Singapore to China.
Masthead code zeros will transform the boats’ performances upwind in the light which will most likely see teams carrying these giant masthead sails in up to 8.5 to 9 knots of true wind speed which will see the boats travelling faster than the wind speed at 40 degrees true.
Boat speeds of 11 knots in just 9 knots of true wind will not be uncommon and teams may well decide to opt to take four upwind sails on a leg and drop one of the spinnakers given the new emphasis on upwind work.
The new boats will be allowed to measure in 24 sails for the complete trip around the world. The total number of sails may seem high, but when the requirements of each leg are taken into account, managing the sail programme will be one of the biggest keys to success.
While specific wardrobes may vary from boat to boat, a typical sail package for a typical leg might include; one mainsail, three upwind jibs, three reachers which are actually smaller than the jibs, a masthead code zero and five spinnakers.
Making best use of the sail wardrobe and staying in control for longer is another key area and a lesson than the twin-ruddered ABN AMRO boats taught the rest of the fleet in the 2005-06 race.
Clearly designing more power into the new generation is one thing and an area that designers and teams have spent a great deal of time developing, yet harnessing it for a new course with new boats, will be quite another. The second generation may look similar to last time, but their boosted performance looks set to put them in another league.
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