The Aero- and Hydromechanics of Keel Yachts

645 Pages·2015·63.09 MB·English

by  J.W. Slooff (auth.)

The Aero- and Hydromechanics of Keel Yachts
J. W. Slooff
The Aero- and
Hydromechanics
of Keel Yachts
2123
J. W. Slooff
Uithoorn
The Netherlands
Every effort has been made to contact the copyright holders of the figures and tables which
have been reproduced from other sources. Anyone who has not been properly credited is re-
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ISBN 978-3-319-13274-7 ISBN 978-3-319-13275-4 (eBook)
DOI 10.1007/978-3-319-13275-4
Library of Congress Control Number: 2014956974
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To my grandchildren:
Bente, Stan, Jouke, Mirte, Tessa and Laura
Preface
The intended reader will already have found out that this is not a book with glossy
pictures by Beken of Cowes of the glamorous and fabulous sailing yachts of the
world. It is a lot more sober and a little more scientific than that.
This book has come about as a follow-up on a course on the aero- and hydro-
mechanics of sailing that was written by the author for the Heiner Sail Academy in
the Netherlands in 2002/2003. The purpose of the course was to provide yachtsmen
with (top-)amateur or (semi-) professional racing ambitions with a solid background
of the aero- and hydromechanics of sailing. The ambition of the author was to do so
in a manner that he could justify from his own background as a professional fluid
dynamicist and a cruising yachtsman, while trying to keep the material accessible
for attendees without profound academic schooling.
This, of course, is not the first book on the aero- and hydromechanics of sai-
ling. A.C. Marchaj’s “Aero- hydrodynamics of sailing” (ISBN 0-7136-5073-7) is
generally considered as ‘The Bible’ on the science and technology of sailing. And
rightly so; it contains an incredibly broad and deep treatment of almost all aspects
of sailing technology. Many readers, however, may find it difficult to find their
way in Marchaj’s book, in particular if their objective is to find out in a relatively
straightforward way about how and why sail boat performance depends on the con-
figuration and trim of boat and sails.
While working on this book a new, very valuable volume on the science behind
sailing yachts and their design appeared on the horizon: Fabio Fossati’s “Aero-Hy-
drodynamics and the Performance of Sailing Yachts” (ISBN 978-0-07-162910-2).
Fossati’s book provides an excellent description of the state of the art (2007 level)
of fluid dynamic technology as applied to sailing yachts. It also addresses the phy-
sical mechanisms of sailing in considerable depth.
At the other end of the spectrum there are numerous books on the subject of a
more popular nature. Many of these are directed at the yachtsman that is interested
in the ‘what’ and ‘how’ but not too much in the ‘why’ of boat configuration and boat
trim. Few provide explanations of the mechanisms involved in a way that is scien-
tifically justified. An excellent exception is formed by Frank Bethwaite’s “High
Performance Sailing” (ISBN 978-1-4081-2491-8).
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viii Preface
It is the author’s impression that there is a substantial gap between Marchaj’s
‘bible’ as well as Fossati’s ‘volume a vela’ and the more popular books on sailing.
This book tries to bridge that gap. For this purpose the material is presented in a
form that, on the one hand, is scientifically justified and consistent according to
the author’s best knowledge. On the other hand it also aims at facilitating on-board
utilization of the knowledge that is acquired.
It is of course up to the reader to judge whether the author has succeeded in
realising this objective. The author hopes, however, that his 50 years of experience
in fluid dynamics and his 35 years of experience as a (cruising) yachtsman have
contributed to the objective to create a ‘New Testament’ of sailing mechanics.
February 2004/2013 Joop Slooff
Uithoorn, The Netherlands
About the Author
Johannes (‘Joop’1) W. Slooff is a (retired) fluid dynamicist by profession. He is also
a cruising yachtsman (not yet retired).
In 1964 he obtained his degree in aeronautical engineering at Delft University of
Technology in the Netherlands, also having followed the Diplome Course at the Von
Karman Institute for Fluid Dynamics (VKI) in Rhode-St. Genèse, near Brussels in
Belgium.
In 1965 he joined the National Aerospace Laboratory (NLR) in Amsterdam, The
Netherlands, as a research scientist in aerodynamics, with airfoil and wing design
and applied computational aerodynamic design methodologies as his main topics of
research. Much of this research was done in support of and in close collaboration
with the former Fokker Aircraft Company.
In 1976 he was appointed as head of the Theoretical Aerodynamics Department
of NLR and in 1986 as chief of the Fluid Dynamics Division, a position he held
until his retirement in 2001. From 1987 to 2001 he was also a part-time professor in
applied computational aerodynamics at the Aerospace Faculty of Delft University
of Technology.
He has served on several national and international advisory committees such as
the Fluid Dynamics Panel of the former Advisory Group for Aeronautical Research
and Development (AGARD) of NATO, the Research and Technology Organisation
(RTO) of NATO, the Applied Aerodynamics Committee of the American Institute
for Aeronautics and Astronautics (AIAA), the Group for Aeronautical Research and
Technology in Europe (GARTEUR), the Technical Advisory Committee of the Von
Kármán Institute for Fluid Dynamics in Belgium and the Scientific Advisory Coun-
cil of the Maritime Research Institute of the Netherlands (MARIN). In 1996 he de-
livered the 36th Lanchester Lecture for the Royal Aeronautical Society in London.
He is the 1997 recipient of the Von Kármán Medal of AGARD/NATO, in recogni-
tion of his outstanding contributions to that organisation. He is also a Fellow of the
American Institute for Aeronautics and Astronautics.
His activities in sailing started in 1977 with the acquisition of a 28-foot crui-
sing sloop. In 1980 he became involved, through MARIN, with the development
1 Pronounced as “Yoap Sloaf  ”.
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x About the Author
of the 12-m yacht Australia II for the 1983 America’s Cup campaign. He proposed
the concept of the winged keel and was responsible for the computational fluid
dynamic modelling, performed at NLR, that substantiated the performance poten-
tial of the concept2. In the 1980s he was also involved in keel research performed at
Delft University of Technology by Gerritsma and Keuning.
After his (early) retirement in 2001 he wrote a course on the aero- and hydrodyna-
mics of sailing for the Heiner Sail Academy.
He also became involved, as a technical-scien-
tific advisor, in the ABN-AMRO campaign
for the 2005–2006 Volvo Ocean Race.
From 2008 through 2012 he has lectured on
the aero- and hydrodynamics of sailing at an
annual special course on sailing yacht techno-
logy at the faculty of Maritime Technology of
Delft University.
He is (co)-author of about 40 conference
papers and journal articles on fluid dynamic
topics, including some on the hydrodynamics
of sailing yacht keels.
Since 1986 he owns a 33-foot cruising
sloop with a shallow draught winged keel and
winged rudder of his own design.
…when tide and wind are gone:
drying out on a winged keel…
2 For an account of his involvement see: “Who really designed Australia II?” by Barbara Lloyd,
Nautical Quarterly, Spring 1985.
Acknowledgements
No one works completely alone and, although I have done almost everything for
this book by myself, there are a number of people that have played an essential
stimulating or supporting role.
My addiction to the science of sailing probably started around 1980 when Peter
van Oossanen, then project manager at MARIN, asked me to join him in the design
research for the America’s Cup winning, 12-m yacht Australia II.
About 30 years later Alexander Vermeulen, long-time friend from my years of
studying in Delft, and once-a-year sailing mate, volunteered to, critically, proof-
read what I had produced for this book. Sadly, he did not live long enough to wit-
ness the completion of our work. He died while scrutinizing Chap. 6.
Jouke van der Baan, another long-time friend from my years of studying in Delft,
my co-skipper once a year, when we sailed a week or so around the Frisian Isles
with Alexander Vermeulen, continued the proof-reading where Alex had stopped.
Lex Keuning, recognized expert in ship hydromechanics, with whom I shared a
common interest in sailing and its technology since we first met over 35 years ago.
He kept me up-to-date in sailing yacht technology during the decade when I was too
busy to keep track of what was going on. More recently he gave me the opportunity
to share my knowledge on the scientific aspects of sailing with the students and the
other lecturers of the annual, so-called ‘minor’ course on the technology of sailing
at Delft University of Technology.
Roy Heiner, professional racing yachtsman, gave me the opportunity to play a
small role in the ABNAMRO Volvo Ocean Race campaign and to learn what ocean
racing people consider to be important.
Last but not least my best and oldest friend Robbert van der Mije, sailing and
travel companion for many, many years, always searching the internet for news on
sailing that he thought I could use.
Finally my wife Lia, whom I should have mentioned first and before all. When
I retired after a fairly busy professional career she must have thought that, finally,
it was her turn to receive attention. Not quite so, I am afraid. After half a year of
cleaning up and completing some technical/scientific work that I had started, but
never finished, during my time at NLR, I was caught, once more, by the science of
sailing. Again, my wife did not get the attention she deserved, without complaining.
I beg her to forgive me for my addiction.
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