5. Ultimate sail loads

5.1 Analysis of the critical load concept

The concept of critical elastic buckling load is associated with an ideal plate. Consequently :

• it postulates an indefinitely elastic material, whereas the latter has a finite yield point;

• it ignores structural imperfections, in particular the presence of residual stresses resulting from manufacturing procedures (rolling of sheets and sections used for stiffening) and fabrication (welding to join sheets together and fix the stiffening);

• it assumes that the plate is initially perfectly flat, and thus ignores any geometric imperfections, in particular the inevitable flatness defects resulting from rolling, but above all from the...