The third module in
the workflow is the simulation of the rig. Classical
wing theory can be used to calculate the forces acting on the sails.
The theory relies on the input of the aerodynamic characteristics of
the 2D sail sections. As a prerequisite, the program XFOIL was used to
create a database
of discrete values of the required coefficients. The theoretical
background can be found in this report.
A program Sail2D was written that interpolates in the database. It can
be downloaded here.
With these coefficients Prandtl's lifting-line
method can be used to calculate the 3D-flow around head- and
mainsail. Each sail is divided into 31 panels. The designer will get a
detailed distribution of angles of attack and force coefficients across
all panels. It is possible to optimize the trim parameters for maximum
driving force. The
theory and the validation of the program are described in this report.
Details of the program are
explained in the user's manual that can be downloaded here:
UliSail User's manual:
A zipped file with the
program UliSail_2.2 can be downloaded here
(click on picture)
If you need a CAD-model of your sails, created with UliSail, you can send an e-mail to: ulrich(at)remmlinger.com