Design team’s search for
speed and reliability
Designing and building an America's Cup
yacht is a complex undertaking which involves a team with
skills, experience and training in many areas.
The Emirates Team New Zealand design team
numbers 19 and includes naval architects, composite structural
engineers, mechanical engineers, appendage designers, software
engineers and data analysts.
They have access to massive computing power
and the best possible software. And more important, they
have experience and intuition gained from participation in
several America’s Cup campaigns and many other sailing
projects.
They make use of the latest materials and
boat building techniques. The hull, deck, bulkheads and many
of the deck fittings including wheels and winches are made
from carbon fibre as is the mast. Carbon fibre is a major
component of sails and some of the rigging.
The team’s goal is not only to build
fast yachts, but to achieve strength and reliability for
the least possible weight. They must be innovative and push
the limits but must maintain a balance.
It is about designing and building light
carbon fibre structures that can withstand enormous loads
and great punishment in testing and racing.
If they design and build a structure that
is too light it will break under load; build one that is
too heavy and the yacht will not be competitive. The weight/strength
compromise is a delicate balance.
Memories of one Australia breaking in half
and sinking off San Diego in 1995 and Young America folding
up in the Hauraki Gulf in 1999 provide sharp and constant
reminders that the yachts have to withstand severe punishment.
Building with carbon fibre involves laminating
layers of material; structures can be built with great precision,
ensuring the strands of fibre run exactly along the load
lines for maximum strength and that there is exactly the
right build-up of layers, more in the high-load areas and
fewer in the low-stress areas.
Certain areas, particularly where the keel
attaches to the hull, require much more strength. Also, the
hull and deck on their own would create a quite fragile shell
that would never be up to the demands. Internal framing and
reinforcement are required to give the structure strength.
An America’s Cup design team tends
to be secretive. The competition is more than a few yacht
races. It is a battle of design and technology and the secrets
are well guarded.
The team gathers a vast amount of information
at regattas, during testing programmes, from weather analysis
and from design research.
Sailing and design team work together to
distil everything they have learned into a design philosophy.
They define the kind of yacht they believe will perform best
off Valencia in 2007.
Designers rely on computer simulations,
but amazing as the software might be, there can be some disparity
between simulated results and what happens when the yachts
are built. To narrow the gap, the team constantly refines
computer software and tests scale models in tanks and wind
tunnels.
Emirates Team New Zealand's tank tests
use 1/4 scale models at a 250m long towing tank in the south
of England. The models are fixed to a carriage and can be
run the length of the tank in various configurations of heel
to simulate different sailing modes.
Designers have to work within the America's
Cup Class rule, which is a formula involving relationships
between length, sail area and displacement.
The designers have to trade these dimensions off against
each other within set limits. Nothing comes without a price.
For example, if they add a bit to the sail area it has an
impact on either the length, or the displacement, or both.
A fast hull shape is important, but a hull
has to work with the keel, bulb and rudder and with the rigs
and sails. Sails are tested in the University of Auckland’s
wind tunnel which twist the flow of the wind to simulate
the wind sheer that takes place between the base of the mast
and the top of the mast.
The designers strive for that little extra
edge that will give the team an advantage on the water. But,
because the rule has been in existence since the 1992 San
Diego regatta, the chance that a team has to make a big advance
is limited. Their aim is to accumulate a number of small
advances that refine the boats and give them that elusive
edge. |
