Feature 1
nor are they very much like skiffs, which implement the kspline in the Friendship
are generally sailed flat, not heeled. The Framework, a parametric hull modelling
new hull series should be developed from and computer-aided engineering (CAE)
recent planing keelboat hulls. It would system. This system was an ideal host for
also cover a range of shapes that might the kspline, because it allows a designer
be suitable for next-generation designs, to define a hull shape by creating a
which would be lighter than present-day set of lines, such as waterlines and
boats because they would be built from sections. Crucially, this software skins
more advanced materials. the designer’s framework with a set of
When Raymond visited Auckland faired bspline surfaces, fully compatible
in December 2008 for the Royal with industry-standard analysis, design,
Institution of Naval Architects (RINA) and manufacturing software. Testing
High-Performance Yacht Design
hull number 14 from raymond’s systematic
and practice had shown that the kspline
conference, he had been thinking about
series (credit: Jérémie raymond).
integrates well with Friendship’s existing
how he might create this systematic series design tools, including the fspline, a fair
of hull shapes. He needed a system that two-dimensional curve.
would integrate well with computational perspective, it was interesting because The author’s demonstration was based
fluid dynamics (CFD) applications, so it its shape is controlled by the values of a on a medium-displacement cruising
was essential to use software that would small number of parameters. Used as an yacht hull. To show how a designer might
produce a fair surface. Only specialist hull underwater section, the curve is defined use the kspline, he created a family of six
modelling software would do. But he knew by its breadth, depth, cross-sectional area hulls. All of these hulls shared the same
it would be a tedious and time-consuming (with respect to a horizontal datum such centreplane and waterline curves, and
task to create his hulls with existing yacht as a waterline), deadrise angle, and two because he did not alter the immersed
design software. parameters that control the curvature in area of any section, all six hulls had the
That was before he heard about the the floor and bilges. Adjusting the value same nominal displacement. Heeled
Friendship Framework and the kspline. of any parameter modifies the shape. at 30 degrees, their waterlines showed
The kspline was developed by the The author attended the conference noticeable differences.
author, New Zealand yachtsman and to introduce his invention to the yacht But that was not what captured
writer, Kevin Cudby. It was designed design community. Over the previous Raymond’s attention. The demonstration
for creating parametric section curves year, he had worked with Potsdam- hulls had been created on a low-cost
for yacht hulls. From Raymond’s based Friendship Systems GmbH to laptop computer: The little number-
cFD simulation of
hull number 1 at a
trim angle of one
degree, and a
boat speed of 25kts
(credit: Jérémie
raymond).
Ship & Boat International March/April 2010 27
SBI_MarApr10_p26-27-28.indd 27 26/02/2010 12:22:21
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