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| Sport and sprit boat sailors now
can choose between GRADIENT AP reaching molds optimized for point-to-point
racing (above) and TrueMax runner molds (see below). |
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| Windward / leeward racers
benefit from a "runner" mold (above) optimized for deeper downwind
angles with a higher draft and fuller head designed to rotate the sail
to windward out from behind the mainsail. |
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GRADIENT SERIES
Asymmetric and Symmetric Spinnakers
Significant advances in design software and wind tunnel testing
have spurred a surge in downwind sail development at North Sails.
Experts have long known that your biggest gains can be achieved after
you round the windward mark. It's the reason why North Sails invests more
R&D dollars in downwind sail development than any sailmaker. Although
North's revolutionary 3DL molded sail technology has captured headlines
in the past few seasons, our downwind sail development has been progressing
at an equal pace. Advances in design and production software, combined
with a breakthrough in wind tunnel testing, have launched a new family
of North downwind sails that are both faster and easier to trim over a
broader wind spectrum.
The tunnel talks. Wind tunnel
testing is nothing new in sailmaking, but a collaboration between North
Sails, Team New Zealand and the Department of Mechanical Engineering at
the University of Auckland has given it a new twist. Unlike other facilities
that test sails in uniform wind flow, the new wind tunnel produces a "twisted
flow" that more accurately simulates the boundary layer and vertical
wind shear experienced by boats on the water. Because the water's surface
has friction, and because there is more wind at the top of the mast than
at deck level, both apparent wind speed and apparent wind angle change
as you move up the mast. Initial testing in the twisted flow wind tunnel
was performed shortly before the 1995 America's Cup, with designers achieving
significant increases in driving force over first generation designs. Recently,
North designers from around the world tested 31 new downwind and reaching
sail designs in apparent wind angles from 25-150. Scale models for both
pole-rigged and sprit-rigged boats were tested, including masthead and
fractional sail configurations plus different sheeting points for each
sail.
The results were dramatic, not only identifying designs that were significantly
faster, but also improving our understanding of the relationship between
driving force, drag and heel.
The result is the powerful new North GRADIENT SERIES of symmetric and asymmetric
spinnakers. At press time, eight of nine Whitbread Round the World Race
syndicates are using GRADIENT SERIES downwind sails for the '97-98
event. Whitbread boats carry a limited downwind inventory in conditions
ranging from Doldrums to hurricanes, so a sail that can be carried over
a wider range of wind strengths and angles is an enormous advantage.
Today's generation of lighter, faster-accelerating offshore one-designs
and sportboats also experience huge fluctuations in apparent wind speed
and direction. For these boats, GRADIENT SERIES spinnakers will deliver
more drive more of the time. All GRADIENT SERIES designs are optimized
using North's Flight and Flow / Membrane™ design analysis software (integrating
data from the twisted flow wind tunnel) and are molded both horizontally
and vertically using North's proprietary Spine™ 3D shaping program. The
result is a profile that is exceptionally fair for smoother flow, improved
stability and easier trim.
Asymmetrics go mainstream. The emergence
of sportboat classes, sprit-rigged racer/cruisers and developments spurred
by America's Cup and Whitbread racers have pushed Asymmetric spinnakers
into the mainstream of modern sailing. The twisted flow wind tunnel has
been a powerful tool in North's Asymmetric development program, identifying
shapes that are more forgiving to fly and produce more forward drive in
relation to heeling force. North Gradient Series Asymmetrics are now offered
in Reacher, Runner and VMG models that allow you to match your asymmetric
to your style of racing. North's Asymmetric Runner, for instance, is larger
and fuller than the asymmetric reacher, with maximum girth carried higher
up in the head of the sail. This helps rotate the sail to windward, out
from behind the mainsail for improved performance at the deeper wind angles
common to windward/leeward courses.
After thousands of miles of sea trials on Whitbread boats, North Asymmetrics
are also being offered with a contrasting dark luff option. This eases
eye strain in daylight and makes the luff more visible in low light conditions.
All of this development has also given North personnel a clearer picture
of where Asymmetric and Symmetric spinnakers overlap on the performance
spectrum. Different rating rules treat Asymmetric and Symmetric spinnakers
differently, and there are times when a boat may be better served by an
All-Purpose Symmetric Reacher / Runner. Your North representative can help
you make the best choice for your boat and crew. |
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The "twisted flow" wind
tunnel is the first in the world to simulate real world differences in
apparent wind speed and wind angle between deck level and the upper part
of the rig. Scale models for both pole- rigged and sprit- rigged boats
were tested in the twisted flow wind tunnel. |
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RECENT RACE
RESULTS FOR NORTH GRADIENT SERIES SPINNAKERS
CMAC
1-2-3-4-5-6-7-8-9-10 overall
Whitbread Race
1-2-3-4-5-6-7 overall
(to date)
ILC-40 World Championship
1-2-3-4-5-6
Rolex Maxi World Cup
1-2-3-4-5-6
European IMS Championship
IMS 1 & 2
1-2-3-4-5-6-7-8-9-10
German IMS Championships
IMS 1: 1-2-3-4-5-6-7-8
IMS 2: 1-2-5-6 |
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