This maximizes the Long-EZ’s CG envelope and minimizes the required wing sweep whereas the Vari-EZ wing needs more sweep to keep the neutral point far enough aft with the GAW1 airfoil. The E1230 airfoil has a steeper lift curve and smaller pitching moment than the GAW1. Airfoils with large pitching moments load up the canard and restrict the forward CG, or they require a larger canard which moves the neutral point forward. An airfoil with a low moment coefficient (Cm) will allow the aircraft’s CG to be farther forward. The wing’s pitching moment determines the aircraft’s forward CG limit. The steeper the curve, the farther aft the neutral point will remain. For a given set of parameters, the wing’s lift curve determines how far the neutral point moves forward as alpha increases. To combat this, the wing’s airfoil should have the steepest lift curve possible. This moves the neutral point forward and decreases the stability margin. The canard is a flapped airfoil and its lift coefficient (CL) increases at a faster rate than the wing as their angle of attack increases. In short, the following airfoil qualities had a major affect on pitch stability and CG range: A pattern developed in the aircraft’s response to different airfoils. Why would Burt specify an older, draggier airfoil for the Long-EZ? I learned the answer while investigating the Cozy wing using Airplane PDQ. The E1230 is a forward loaded, turbulent flow airfoil with higher drag than the GAW1. Burt then designed the Long-EZ in 1978 and selected the Eppler 1230 airfoil, which he also modified to reduce pitching moment. He modified the cusp to reduce its pitching moment, but the section remained a modern (at the time) laminar flow, high-lift airfoil. Airfoil Design “Airfoil optimization requires the application of science, intuition, and perseverance” When Burt Rutan designed the Vari-EZ in 1974, he selected NASA’s GA(W)-1 airfoil for the wing.
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