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With the continually rising cost of fuel, the demand for more
fuel-efficient vessels seems only logical. This paper outlines
the author’s significant gains in this area over 14 years of
research and development in appendage design with appli-
cation to long-range displacement and semi-displacement
vessels.
INTRODUCTION
This paper is a follow-up to the work published in the SNAME
2000 paper
Development of a 47-foot Modern Trawler
Yacht.
That paper discussed the work done to date and its
application in a small ocean-going yacht. Since that time
the volume of work has expanded considerably as well as
being applied to larger vessels both in retrofit and new-build
construction. For those who have not had the opportunity to
read that paper and/or are not familiar with this work, here
is a brief recap.
Over 14 years ago, the author initiated an in-house research
project with the goal of increasing the efficiency of long-
range motoryachts. The intent was to achieve a hull form
that was efficient over a wide range of displacement and
high semi-displacement speeds. The basic scenario was for
a long-range vessel capable of serious ocean passages such
as transatlantic or better, at displacement speed, with a
comfortable motion, good stability characteristics and with
very good fuel economy. Once over to the Mediterranean or
other long distance cruising waters, the vessel could power
around at higher semi-displacement speeds in order to keep
up with faster local yachts, while still maintaining the same
high degree of comfort and fuel efficiency, and then return
across the Atlantic in a displacement mode. This would b
achieved not by re-inventing naval architecture, but inste
refining it by utilizing and enhancing the current technolo
A comparable analogy would be the progression of the in
nal combustion engine, from the first inefficient version t
its modern-day efficiency. One of the first engines (1890)
was a 1.1 liter motor capable of 4 hp @ 900 rpm (Daimle
Maybach).
Today that same size production motor with today’s effici
carburetors, turbo chargers, header exhaust, fuel injectio
and careful intake and exhaust porting can develop over
100 bhp @ 6000 rpm while still being lighter and more fu
efficient than the original model. The basic principles of
combustion and even the general design of these motors
have not changed greatly from the initial concept but fine
tuning the design has brought huge gains. Much of this h
been brought about by bolting on better carburetors, tune
air intake and exhaust systems, etc. In that same spirit, t
principles of a good basic hull design were evaluated and
then methods looked at to increase efficiency by utilizing
enhanced “bolt-on” appendages.
Market Response:
The main reason any of this work is even made possible i
the huge and still-growing interest in long-range motor-
yachts, also known as passagemakers. As aging baby-
boomers retire with a record amount of wealth, in good
health and with a thirst for adventure, they look to the ca
bilities of the fishing trawlers and crabbers and ask if it is
possible to achieve that seaworthiness in a motoryacht.
By Patrick J. Bray
Bray Yacht Design and Research
www.brayyachtdesign.bc.ca
Fig. 1 Fox 86, Config. A
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