Volvo Ocean Race: Volvo Open 70 boat design explained
What goes into making the boats that take part in the Volvo Ocean Race? Plenty, it turns out. And season after season, much work goes into making sure the vessels are ultra-competitive.
In reviewing the rules that govern the design and construction of the Volvo Open 70, the focus was on refinement rather than radical changes. Understanding the loads that these powerful machines generated downwind was one of the areas that focused 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 increased to 14.00-14.50 tonnes, while a maximum keel bulb weight of 7.4 tonnes was set.
Above deck, all spinnakers are allowed to be furled, a move that will help make the sail plans more manageable for the crew as well as reducing development costs.
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 - where the fin must weigh a minimum of 1,900kg - 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 the 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 the boat for Abu Dhabi Ocean Racing.
Rig development is easy to identify at the dockside and it will be interesting to see how many teams adopt the jumperless rigs used on the Telefónica boats in 2008-09. 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 is important.
Consequently rigs are clean, 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 be built using high modulus carbon fibre which means stiffer rigs than can be smaller in section at the top to further reduce windage, although there is a balancing act to perform here with the higher topmast loads associated with the masthead upwind genoas.
The rules for 2011-12 have reduced the maximum number of sails and the teams will have to completely rethink their sail plans and wardrobes. 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.
Masthead code zeros increase 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 17 sails (down from 24) for the complete trip around the world, plus two In-Port Race only spinnakers. 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, they are limited to one mainsail, two headsails, three spinnakers (one of which must be fractional) and one staysail.
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 third generation may look similar to last time, but their boosted performance looks set to put them in another league.
<p>Fore more information about the Volvo Ocean Race, check out the official <a href="http://www.volvooceanrace.com/en/home.html" target="_blank">Volvo Ocean Race website</a>.</p>