Boat International - June 2018

circumnavigation back in 1973-4.
“Since then it’s always been in the
back of my mind that DSS would
work,” he says, “but like all radical
ideas, taking it forward needed a
great deal of expensive development
work, and the impetus from a client
who believed in it sufficiently to
take a risk.”
After a few false starts it was
Gordon Kay, an experienced
offshore racer and the owner of
Infiniti Yachts, who provided the
impetus. As early as 2001, Kay had
been in talks with Welbourn about
a new “unlimited” maxi yacht, and
after three years of design and tank-
testing the project had progressed to
a complete design that Kay describes
as “pretty cool”.
Sadly, the project was halted
when the sponsor was taken over, but
work on the DSS foil did not stop.
Heartened by the good results from
computer simulations, Welbourn
played around with practical tests
when time allowed, trying out fixed
foils on a variety of scale models and
full-sized sportsboats, as well as
more formal tank-testing at the
Wolfson Unit in Southampton and at GKN in
Cowes on the Isle of Wight. “Not only did these
prove that stability and speed were significantly
increased by the foil,” explains Welbourn, “but
they also gave unexpected results. These
demonstrated a clear reduction in pitching that

made the yacht better upwind in a choppy
sea, while also smoothing the airflow over the
sails, which made them more efficient. This
was our first serious glimpse of success and
enabled Gordon to persuade a client to build
the first Infiniti 37.”
This yacht proved the foil’s eiciency beyond
doubt but, as Welbourn explains, “the foil needs
to travel at a certain speed through the water
before it attains maximum efficiency, and
because of this it was sure to work even better on

a larger, faster boat”. That boat was to be

Maverick, designed to be the world’s fastest 14

metre, with a specific aim to win ofshore races

of 600 miles or more with a Corinthian crew of

just six. It was a tough ask, but one thatMaverick

has delivered with some significant class victories

and second place overall in both the RORC

Middle Sea and Transatlantic races.

Maverickalso demonstrated the adaptability

of the foil system as the yacht’s midships, where

her DSS foil case would normally be fitted, is

occupied by her canting keel mechanism. So

instead of a single through-hull foil case that

would allow a foil to be deployed on either side of

the hull,Maverickhas two scimitar-shaped foils

that retract into sheaths positioned in the bows

of the yacht. “While being slightly heavier than a

simple through-hull mechanism,” says Kay, “this

system brought another unexpected benefit:

when gybing in strong winds – a nightmare

scenario for most sailors – both foils could be

extended to give her the reassuring stability of a

child’s bike with trainer wheels!”

Maverickis certainly fast and, despite

a handicap system that tries to level the playing

field for all competitors, she is a regular race

winner. But, surely, this is of little interest to

the owner of a bluewater cruising superyacht?

There is one person who disagrees, and he is the

experienced owner of a string of significant

cruising sailers, the last of which wasCanova,

a 34 metre Baltic 112. “Canovawas my fourth

Baltic and my first custom build,” he says, “and

she was specifically designed to make a cruising

circumnavigation with a minimum number of

in-port stopovers. This meant that she had to be

safe, comfortable and perform well.”

The challenge to designers Judel/Vrolijk

was, therefore, to provide suicient fuel capacity

and storage to permit such autonomy, while

maintaining excellent sailing performance.

Launched in 2011,Canovaproved pretty

successful. “My family and I made the cruise,

and while we never made the anticipated

circumnavigation, she performed magnificently

on three Atlantic crossings as well as the

intervening cruises.” But, he adds, “we didn’t

get it absolutely right as there are always

improvements to be made. We could have

done with more volume, and then there was the

“Likeallradicalideas,it

needed a great deal of

expensive development”

http://www.boatinternational.com | June 2018

Pitching

reduced

• therefore
  smoother
  airflow

Forward force

increased

Heeling

force

Lift

Foil also provides

fore and aft stability,

reduces pitching and

makes airflow across

sails more efficient thus

giving improved drive

Lighterkeel=lighterboat,which

meansbetteracceleration

Aero/hydrodynamically

shaped foil adds to

righting moment,

allowing lighter keel

●Sailing boat

equipped with

Dynamic Stability

System (DSS) foil

●Normal sailing boat

Sails drive

boat forward...

...but also

cause boat

to heel

Drag of hull

and keel

As boat heels,

averyheavy

keel counteracts

heeling force

(righting moment)

ILLUSTRATION: SON OF ALAN - FOLIO ART