Relax II. Aeroelastic membrane computation


Relax II has been developed over many America's Cup campaigns and many complex membrane design projects. It incorporates all we have learned in 20 years of practice.

Relax II is a complete interactive, fully non-linear Finite Element code to analyses fabric structures using a state of the art relaxation method.

Relax II's special sail analysis features make it extremely efficient for modelling the most innovative sailplans. It's unique flexibility enables it to predict the behaviour of almost any large-displacement structure. Unlimited accuracy is attainable due to it's sophisticated meshing controls and it's advanced elasticity models (including the critical anisotropic wrinkling capability) .

Relax II's parametric capability combined with it's goal-seeking and optimisation features make it a powerful tool for inverse design.

Relax II's comprehensive interfacing and flow control tools permit it to be integrated into a wider system for such tasks as aeroelastic analysis, yacht performance or a full multi-user yacht simulator.

Relax News:

RBS: Relax II analysis for medium size sailmakers

SailPack is fully compatible with Relax II

New features for innovative development & team working

Relax II brief Specifications:

Parametric preprocessor specifically for membrane structures, accepting model description by combinations of:

•  Unstressed 3D shape

•  Cutting pattern

•  X-Y-Gaussian Curvature.

Data interfaces

•  Specific to the sailmaking industry.

•  Public format

Material modeling:

•  Filament-laid and/or Orthotropic materials.

•  A good wrinkling model.

Bending elements, slide lines, etc.


Nonlinear FEA.

Program Flow control for the aero/structural iteration.

Aero code control by:

•  Linked code

•  Shell

•  Socket.

A constrained optimizer geared for expensive samples.



•  Full 3D graphics using Techsoft's HOOPS.

•  Deformed shape output in various public file formats.

Database interface

•  output for run logging.

•  input for batch control.

Socket connections

•  External control of the code by another

•  Control of external processes

A macro language.





strOOna is a low-cost large-deflection stiffness-based finite element code with a programmable object-oriented database.

strOOna's superelement creation facility provides the active mast to Relax II using it's scripting language and socket communications.

strOOna is a powerful tool for exploring and developing rules-based structures. It is especially efficient for the formfinding of structures where conventional methods would be unstable, such as membrane/arch combinations and automatic tuning of yacht masts.

strOOna's large-displacement formulation permits rotations up to 180 degrees.

StrOOna News:

December 2003. Version 2.3 has a significant improvement in accuracy and stability at large deflections.