Advanced Search provides additional search options providing the ability to narrow your search by combining multiple search variables.
Note that by default, the Date Range set to 2017 will return all results from a text search. You can select both Date Range settings to narrow the returned results.
Velocity prediction programs (VPPs) are valuable design tools that allow designers to parametrically study yacht
performance. The three main components of a VPP are an aerodynamic force model, a hydrodynamic force model and an algorithm
to balance the forces. VPP force models can be derived from many sources such as model testing, empirical or analytic formulations,
computational fluid dynamics (CFD) or often a combination of these. This paper describes an approach to VPP force modeling based
on Reynolds Averaged Navier Stokes (RANS) CFD. RANS CFD captures turbulent flow effects important for sailing such as
separation, viscous drag and wakes. The aerodynamic forces are calculated using steady state RANS and the hydrodynamic forces
are calculated using free surface RANS Volume of Fluid (VOF) with OpenFOAM. VOF simulations are computationally expensive
and many data points are needed for the VPP force models. A cost effective approach to running VOF simulations using OpenFOAM
and cloud computing is described. This approach allows the method to be used on a wide range of projects and not only those with
large R&D budgets such as the America’s Cup and Volvo campaigns. The force models are derived by direct interpolation of CFD
data using both structured and unstructured data point sampling. As a test case the method is applied to analyze three keel options for
a 125’mega-yacht as well as make comparisons to flat water sailing performance. Modelling turbulent flow effects is especially
important for mega-yachts because they have many drag producing design features.
A Refinement of the Methods Used to Determine the Balance of a Sailing Vessel during the Design Phase, with Application to Sail Design and Subsequent Sail Selection and Sailing Operations
The thrust of this paper is, first, to attempt to define the
relationship between the individual sails, both together and
separately, and the hull with somewhat more precision, and
secondly, to develop a calculation tool to better establish
this relationship, and to better anticipate the vessel's over
all sailing behavior. Because of those factors that effect
balance including and beyond those addressed by the
traditional design approach as taught by most current texts
on sailboat balance, the need for the factor "lead" will
never go away. However, by including, as will be
demonstrated, an additional balance factor, specifically the
longitudinal sheet positions, into the balance equations
during the design phase, sailboat balance can be predicted
with better accuracy. The primary objective of this
refinement will be the ability to design sail profiles,
especially the complement of headsails, which will result in
the least (adverse) change of balance when changing from
one headsail to another, and which can be applied to either
new designs, or to existing boats in need of out-of-balance
remedies. This would mean that each anticipated sail
combination can be analyzed for its lead, and therefore
adjusted during the design phase to insure that proper helm
is maintained from one combination to the next.
Uncertainties in the Wind-Heel Analysis of Traditional Sailing Vessels: The Challenges it Presents for Forensic Analysis of Sailing Vessel Incidents
There are many uncertainties in the interpretation of
full-scale sailing vessel data taken under dynamic
conditions, and even more uncertainties when
forensic analysis is attempted based only on
survivor’s recollections. Frequently, the analysis is
based on static equilibrium assumptions, sometimes
modified to steady-state motions of the wind and
heeling response of the vessel. Dynamic conditions
are generally non-deterministic and statistical
methods must be used. Even more complicated is the
non-stationary random process nature of most
accidents.
In the wind-heel research carried out on Pride II, it
has been shown that wave action frequently adds
uncertainty to the correct attribution of contributions
to establishing the cause of the resulting heeling
action. The best data are found in steady 10 to 20
knot wind strengths in minimum waves found in the
lee of a shoreline. This criteria can be interpreted as
minimizing the uncertainties in characterizing the
wind-heel performance of a given sail combination at
normal angles of heel...
The Effects of Streamlined Rigging on Sailboat Performance
The design of sailboat rigging influences the yacht's performance through the change in vertical center of gravity. windage, and ability to control the shape of the rig. In the past, designers have attempted to minimize this drag through the use of streamlined shapes...
The Influence of Heel on the Bare Hull Resistance of a Sailing Yacht
For the useful prediction of the performance of a sailing yacht using a generic Velocity Prediction Program (VPP) an accurate assessment of the hydrodynamic and aerodynamic forces and moments involved is essential...