Just a quickie: This week I painted this again to have a better image in the script of my aerodynamics lecture. I learned something about CAD-programs in the meantime. Basically, it is the result of some theoretical considerations about multi-wing configurations for minimized induced drag; done in late 2008. Despite the cross-influence between both planes, a biplane has actually a lower induced drag than a monoplane for a given total wing span and weight. This is because, when the distance between the planes is greater than zero, the mentioned cross-influence is always weaker than the induced velocities imposed on a lifting vortex by its own wake vortex sheet. In this particular case there are two pairs of wings with an aspect ration of 40 each that provide a lifting surface equal to a monoplane having AR=20. However, the induced drag calculated by a lifting line method delivers an induced drag that is equal to a AR-27-monoplane. On the other hand Reynolds-number are only half of the respective monoplane, leading to limited maximum lift as well as higher viscous drag. Major problems are probably structural issues originating from the slender wings or, more likely, from torsion in the open cockpit section between those two large moments of inertia. ---------------------------------------------------------------------------- Three view added. the Wheelchair General CVI Labwindows 4.0.1 Grapher 2.0.3 AutoCAD 2011 Corel Photopaint 7 Notepad